If your OBD-II scanner displays P0112, your vehicle’s Engine Control Module (ECM) or Powertrain Control Module (PCM) has detected an abnormally low-voltage signal from the Intake Air Temperature (IAT) Sensor 1 circuit.
The generic OBD-II definition for P0112 is:
Intake Air Temperature Sensor 1 Circuit Low Input
Despite the words “low input,” P0112 usually does not mean the intake-air temperature is too low. It means the electrical voltage in the sensor circuit is below the PCM’s expected range.
Because most Intake Air Temperature sensors use a negative temperature coefficient thermistor, low signal voltage is interpreted as an extremely high intake-air temperature.
Depending on the vehicle, the scan tool may display an impossible reading such as:
- 250°F
- 275°F
- 300°F
- The highest temperature supported by the PCM
The sensor may actually be shorted internally, the signal wire may be shorted to ground, or the connector may be contaminated with moisture or conductive debris.
Replacing the sensor without testing the circuit can turn a simple wiring repair into another episode of “parts cannon diagnostics,” where perfectly good components are replaced until the owner’s wallet develops its own warning light.
Alternate Manufacturer Definitions
Depending on the manufacturer, scan tool, or service information, P0112 may appear as:
- Intake Air Temperature Sensor 1 Circuit Low
- Intake Air Temperature Sensor Low Input
- IAT Sensor Circuit Low Voltage
- Intake Air Temperature Signal Low
- Intake Air Temperature Sensor Short to Ground
- Intake Temperature Sensor Voltage Too Low
- Air Intake Temperature Sensor Circuit Low
- Charge Air Temperature Sensor Circuit Low
- IAT Sensor 1 Signal Below Threshold
- Intake Air Temperature Sensor Short Circuit
- Intake Temperature Signal Implausibly High
- Intake Air Temperature Sensor 1 Low Voltage
Although the wording differs, the underlying problem is similar: the PCM sees less voltage than expected on the Intake Air Temperature Sensor 1 signal circuit.
P0112 Quick Facts
| Item | Information |
|---|---|
| Diagnostic code | P0112 |
| Generic definition | Intake Air Temperature Sensor 1 Circuit Low Input |
| System | Engine air intake and fuel management |
| Fault category | Electrical circuit low |
| Sensor type | Negative temperature coefficient thermistor |
| Typical scan reading | Extremely high intake temperature |
| Severity | Low to moderate |
| Safe to drive? | Usually for a limited time |
| Most common causes | Shorted sensor, signal wire shorted to ground, damaged connector |
| Typical repair cost | $50–$600+ |
What Does the P0112 Code Mean?
The PCM supplies or monitors voltage through the Intake Air Temperature sensor circuit.
The IAT sensor changes resistance according to incoming-air temperature. The PCM then converts that voltage signal into a temperature value.
On most vehicles:
- Colder intake air produces higher sensor resistance.
- Higher resistance produces higher signal voltage.
- Warmer intake air produces lower resistance.
- Lower resistance produces lower signal voltage.
When the signal voltage falls below the calibrated threshold for a specific amount of time, the PCM stores P0112.
The PCM may interpret this low voltage as an extremely hot intake-air condition, even when the actual air entering the engine is cool.
Does “Circuit Low” Mean the Air Is Too Cold?
No.
This is one of the most common misunderstandings surrounding P0112.
“Circuit low” refers to low electrical signal voltage, not low air temperature.
Because of how an NTC thermistor works, the relationship is effectively reversed:
| Circuit condition | PCM interpretation |
| High resistance | Cold intake air |
| High signal voltage | Cold intake air |
| Low resistance | Hot intake air |
| Low signal voltage | Hot intake air |
Therefore, P0112 commonly causes the scan tool to show an intake-air temperature that is unrealistically hot.
What Is the Intake Air Temperature Sensor?
The Intake Air Temperature sensor measures the temperature of air entering the engine.
The PCM uses this information to estimate air density and adjust:
- Fuel-injector pulse width
- Ignition timing
- Cold-start enrichment
- Air-fuel ratio
- Turbocharger boost
- Knock protection
- Emissions controls
- Idle strategy
- Electronic throttle operation
- Transmission torque calculations
Cold air is denser and contains more oxygen than warm air. Accurate temperature data helps the PCM determine how much fuel the engine needs.
How Does the IAT Sensor Work?
Most IAT sensors use a negative temperature coefficient thermistor.
A thermistor is a resistor whose resistance changes with temperature.
For an NTC thermistor:
- Resistance increases as temperature decreases.
- Resistance decreases as temperature increases.
The PCM typically monitors the sensor using a reference or pull-up voltage and a sensor-ground circuit.
A simplified example may look like this:
| Intake-air temperature | Approximate resistance | Approximate signal voltage |
| 32°F | High | 3.5–4.5 volts |
| 68°F | Moderate | 2.0–3.5 volts |
| 104°F | Lower | 1.0–2.0 volts |
| 176°F | Very low | Below 1 volt |
Exact resistance and voltage values vary significantly by manufacturer.
Always consult the correct service information before judging a sensor by generic specifications.
What Does Sensor 1 Mean?
“Sensor 1” identifies the primary Intake Air Temperature sensor used by the PCM.
The sensor may measure air temperature:
- At the air-filter housing
- Inside the intake tube
- Inside the MAF sensor
- Before the turbocharger
- Inside the intake manifold
- At the intercooler outlet
- Inside a combined pressure-and-temperature sensor
Some engines use multiple air-temperature sensors.
For example, a turbocharged engine may include:
- Intake Air Temperature Sensor 1 before the compressor
- Charge Air Temperature Sensor after the turbocharger
- Intake manifold temperature sensor after the intercooler
Do not assume the code refers to the first temperature sensor you happen to find under the hood.
Where Is the IAT Sensor Located?
The sensor location depends on the engine and airflow-measurement strategy.
Common locations include:
- Air-filter housing
- Air-intake tube
- MAF sensor housing
- Intake manifold
- Turbocharger inlet
- Charge pipe
- Intercooler outlet
- Combined MAP/IAT sensor
- Combined TMAP sensor
On many vehicles, the IAT sensor is integrated into the MAF sensor.
If the thermistor fails internally, the entire MAF/IAT assembly may require replacement unless the manufacturer services the sensor separately.
How the PCM Detects P0112
The PCM continuously monitors IAT signal voltage.
P0112 may be stored when:
- Signal voltage drops below the calibrated threshold.
- The sensor reports an impossibly high temperature.
- The signal wire is shorted to ground.
- Sensor resistance becomes too low.
- The connector contains conductive contamination.
- The PCM detects a temperature reading outside the possible operating range.
The fault usually must remain present for a calibrated period before the code sets.
Some vehicles may store P0112 immediately, while others require:
- A cold start
- A specific engine runtime
- A certain vehicle speed
- Multiple drive cycles
- Comparison with coolant or ambient temperature
Typical Voltage Conditions for P0112
The exact trigger voltage varies by vehicle, but P0112 often sets when the IAT signal drops near the bottom of its expected range.
A typical circuit may operate between approximately:
- 0.2 volts when extremely hot
- 4.8 volts when extremely cold
The PCM may set P0112 when voltage remains below approximately:
- 0.1 volt
- 0.2 volt
- 0.5 volt
These are only general examples.
Manufacturer-specific diagnostic charts must take priority.
What Temperature Does P0112 Usually Display?
A vehicle with P0112 may display an intake-air temperature near the PCM’s maximum programmed value.
Possible readings include:
- 248°F
- 266°F
- 284°F
- 300°F
- 302°F
- A fixed maximum value
The exact number is not universal.
The important clue is that the reported temperature is far higher than actual intake-air temperature, especially before the engine has been started.
For example:
| Sensor | Cold-engine reading |
| Ambient temperature | 65°F |
| Coolant temperature | 67°F |
| Intake Air Temperature | 284°F |
Unless the vehicle was parked inside an industrial oven, the IAT reading is clearly incorrect.
P0112 Compared With P0110 Through P0114
| Code | Definition | Typical issue |
| P0110 | IAT Sensor 1 Circuit Malfunction | General electrical fault |
| P0111 | IAT Sensor 1 Range/Performance | Implausible or sluggish reading |
| P0112 | IAT Sensor 1 Circuit Low Input | Signal voltage too low |
| P0113 | IAT Sensor 1 Circuit High Input | Signal voltage too high |
| P0114 | IAT Sensor 1 Circuit Intermittent | Signal drops in and out |
A simple way to remember the difference:
- P0110: The circuit has a general problem.
- P0111: The sensor reading is not believable.
- P0112: The signal voltage is too low.
- P0113: The signal voltage is too high.
- P0114: The signal is unstable.
P0112 vs P0113
P0112 and P0113 represent opposite electrical conditions.
P0112
- Signal voltage too low
- Resistance too low
- PCM calculates extremely hot air
- Commonly caused by a short to ground
P0113
- Signal voltage too high
- Resistance too high
- PCM calculates extremely cold air
- Commonly caused by an open circuit or unplugged sensor
This distinction is useful during diagnosis because the live-data temperature often reveals which electrical direction the circuit has failed.
Common Symptoms of P0112
Symptoms vary depending on the vehicle, climate, and PCM fallback strategy.
Common symptoms include:
- Illuminated Check Engine Light
- Extremely high IAT scan-tool reading
- Difficult cold starting
- Rough cold idle
- Engine hesitation
- Poor acceleration
- Reduced fuel economy
- Rich air-fuel mixture
- Lean air-fuel mixture
- Increased exhaust emissions
- Engine surging
- Misfires
- Reduced turbocharger boost
- Retarded ignition timing
- Limp mode
- Failed emissions inspection
Some vehicles may show no noticeable drivability symptoms because the PCM substitutes a default temperature value.
Check Engine Light
The most common symptom is an illuminated Check Engine Light.
P0112 may appear as:
- A stored code
- A pending code
- A permanent code
- A code accompanied by MAF, MAP, fuel-trim, or temperature-sensor faults
The warning light may remain on even if the circuit temporarily returns to normal.
Extremely High Intake-Air Temperature Reading
The clearest diagnostic clue is often an implausibly high IAT reading on the scan tool.
A reading above 200°F on a cold engine strongly suggests:
- Shorted IAT sensor
- Signal wire shorted to ground
- Connector contamination
- Incorrect wiring repair
- Faulty PCM input
Always compare IAT with actual ambient temperature and coolant temperature after a full cold soak.
Hard Starting
The PCM uses intake temperature to calculate cold-start fueling.
If it believes the incoming air is extremely hot, it may reduce enrichment during startup.
This can cause:
- Extended cranking
- Rough initial idle
- Stalling after startup
- Weak cold-weather performance
The problem may be more noticeable in cold climates.
Rough Idle
Incorrect air-density calculations can affect fuel delivery and spark timing.
The engine may:
- Idle unevenly
- Surge
- Shake
- Stall when cold
- Recover after warming up
A rough idle alone does not prove the IAT sensor is responsible, but it supports the diagnosis when combined with an unrealistic temperature reading.
Poor Acceleration
The PCM may alter timing and fuel delivery because it believes intake air is excessively hot.
Drivers may notice:
- Delayed throttle response
- Flat acceleration
- Reduced engine power
- Inconsistent performance
- Limited boost on turbocharged vehicles
The vehicle may feel normal during light driving but weak under load.
Poor Fuel Economy
An inaccurate IAT signal can disrupt:
- Air-density calculations
- Fuel injector pulse width
- Ignition timing
- Cold-start enrichment
- Closed-loop corrections
Depending on the PCM strategy, the engine may operate richer or leaner than intended.
Either condition can reduce fuel economy.
Rich or Lean Operation
Although a low-voltage IAT signal represents hot air, the PCM’s response varies.
Some vehicles may reduce fuel delivery because warm air is less dense.
Others may apply substitute values or protective strategies that result in richer operation.
The final fuel mixture depends on:
- MAF data
- MAP data
- Oxygen-sensor feedback
- Coolant temperature
- Engine load
- Manufacturer calibration
This is why fuel-trim data should be reviewed during diagnosis.
Can P0112 Cause Misfires?
Yes, although misfires are not the most common symptom.
Incorrect temperature data may contribute to:
- Incorrect startup fueling
- Lean operation
- Rich operation
- Spark-timing changes
- Combustion instability
Look for companion codes such as:
- P0300
- P0301
- P0302
- P0303
- P0304
Do not assume P0112 is the only cause of the misfire without completing a full diagnosis.
Can P0112 Affect Turbocharged Engines?
Yes.
Turbocharged engines rely heavily on intake-temperature data for:
- Boost control
- Detonation prevention
- Ignition timing
- Air-density calculations
- Intercooler monitoring
- Component protection
If the PCM believes intake air is dangerously hot, it may:
- Reduce boost
- Retard ignition timing
- Close the throttle
- Limit torque
- Enter limp mode
The result may feel like a major turbocharger problem even though the actual fault is a shorted temperature-sensor circuit.
Can P0112 Affect Transmission Operation?
Indirectly, yes.
Modern automatic transmissions often depend on PCM-calculated engine torque.
Incorrect IAT data may change:
- Calculated engine load
- Torque output
- Throttle response
- Shift pressure requests
- Shift timing
Possible symptoms include:
- Delayed shifts
- Early upshifts
- Reduced-performance mode
- Unusual throttle response
These symptoms are usually secondary to the engine-management fault.
Is P0112 Serious?
P0112 is generally considered a low-to-moderate severity code.
The engine will often continue running because the PCM substitutes a default temperature value.
However, the fault should not be ignored because it may affect:
- Cold starts
- Fuel economy
- Emissions
- Engine performance
- Turbocharger boost
- Knock protection
- Catalytic-converter health
Severity increases if the vehicle also has:
- Misfires
- Lean-condition codes
- Rich-condition codes
- Turbocharger faults
- Stalling
- Limp mode
- A flashing Check Engine Light
Can You Drive With P0112?
You can usually drive a short distance with P0112 if:
- The engine starts normally
- The Check Engine Light is steady
- No severe hesitation is present
- The engine is not misfiring
- The vehicle is not in limp mode
- No overheating or fuel smell is present
Avoid continued driving if:
- The Check Engine Light flashes
- The engine stalls
- Acceleration becomes unsafe
- Severe misfires occur
- Turbo boost is heavily restricted
- The exhaust smells strongly of fuel
- The catalytic converter overheats
A circuit fault that seems minor can become expensive if incorrect fueling damages the catalytic converter.
Can a Dirty IAT Sensor Cause P0112?
Usually not by itself.
Contamination commonly causes:
- Slow response
- Inaccurate readings
- Range/performance faults
- P0111
P0112 more strongly suggests an electrical low-voltage condition.
However, conductive contamination involving moisture, oil, metallic debris, or corrosion may create a path to ground and pull the signal voltage low.
Can a Dirty Air Filter Cause P0112?
A dirty air filter is unlikely to directly cause P0112.
A clogged filter may affect airflow and engine performance, but it normally does not pull the IAT circuit voltage below its electrical threshold.
Check the air filter during diagnosis, but do not expect a new filter to repair a shorted signal circuit.
Can an Aftermarket Intake Cause P0112?
Yes.
Aftermarket intake installation may cause P0112 through:
- Pinched wiring
- Stretched harnesses
- Incorrect extension wiring
- Damaged connectors
- Sensor contact with metal tubing
- Water intrusion
- Incorrect pin placement
- Poor-quality adapter harnesses
The intake pipe itself does not generate the code. The installation and wiring problems around it often do.
Can a Weak Battery Cause P0112?
A weak battery is not a common direct cause.
However, unstable voltage may contribute to:
- Multiple sensor codes
- Communication faults
- Incorrect PCM operation
- Reference-voltage problems
If P0112 appears with several unrelated electrical codes, test:
- Battery state of charge
- Cranking voltage
- Alternator output
- Grounds
- AC ripple
Can a Vacuum Leak Cause P0112?
A vacuum leak usually does not directly cause an IAT circuit-low code.
Vacuum leaks more commonly trigger:
- Lean fuel-trim codes
- Idle problems
- MAP plausibility codes
- MAF performance codes
However, intake work that creates a vacuum leak may also damage or disconnect IAT wiring.
Treat the timing of recent repairs as an important clue.
25 Common Causes of P0112
The most common causes include:
- Internally shorted IAT sensor
- IAT signal wire shorted to ground
- Damaged sensor connector
- Moisture inside the connector
- Corroded connector terminals
- Conductive debris bridging terminals
- Pinched intake-harness wiring
- Melted wiring insulation
- Harness chafing against metal
- Incorrect previous wiring repair
- Reversed connector terminals
- Shorted integrated MAF/IAT sensor
- Failed combined MAP/IAT sensor
- Failed TMAP sensor
- Damaged aftermarket extension harness
- Improperly installed cold-air intake
- Sensor contaminated with conductive material
- Poor sensor-ground circuit configuration
- Short between the signal and ground wires
- Water intrusion from engine cleaning
- Rodent-damaged wiring
- PCM connector corrosion
- PCM connector terminal damage
- PCM software or calibration issue
- Failed PCM input circuit
1. Internally Shorted IAT Sensor
An internally shorted thermistor is one of the most common causes of P0112.
When resistance becomes too low, signal voltage drops and the PCM interprets the reading as extremely hot intake air.
The sensor may fail because of:
- Age
- Heat
- Vibration
- Moisture
- Manufacturing defects
- Physical damage
Resistance testing can usually confirm the failure.
2. Signal Wire Shorted to Ground
The IAT signal wire may contact:
- Engine metal
- A grounded bracket
- Sensor-ground wiring
- Damaged shielding
- A crushed harness section
This pulls the signal voltage low and may produce a fixed maximum-temperature reading.
Inspect the harness near:
- Intake clamps
- Air-box mounting points
- Engine covers
- Turbocharger components
- Battery trays
- Radiator supports
3. Damaged Sensor Connector
A broken or distorted connector may allow the signal and ground terminals to contact each other.
Inspect for:
- Cracked plastic
- Bent pins
- Loose terminals
- Melted sections
- Broken locks
- Terminals pushed backward
Connector damage is especially common after repeated air-filter or intake service.
4. Moisture and Corrosion
Water intrusion can create a conductive path between connector terminals.
Possible sources include:
- Engine washing
- Heavy rain
- Missing connector seals
- Coolant leaks
- Condensation
- Flood exposure
Green or white corrosion indicates that moisture has been present long enough to damage terminal surfaces.
5. Integrated MAF/IAT Sensor Failure
Many vehicles combine the IAT sensor with the Mass Air Flow sensor.
The MAF portion may continue working while the IAT thermistor fails.
This means a vehicle can have:
- Normal-looking MAF airflow
- An extremely high IAT reading
- A stored P0112 code
Test the temperature circuit independently before replacing the full MAF assembly.
6. Aftermarket Intake Wiring Problems
Cold-air and short-ram intake installations often require the sensor connector to be moved.
Problems may include:
- Stretched wiring
- Improper extensions
- Twisted wires
- Crimp connectors without weather sealing
- Incorrect sensor adapters
- Harness contact with sharp metal tubing
Inspect any modification performed shortly before the code appeared.
7. Melted Wiring
Turbochargers, exhaust manifolds, and EGR components generate enough heat to damage nearby wiring.
Melted insulation may allow the signal conductor to contact ground.
Heat damage may be hidden beneath:
- Loom
- Tape
- Heat shielding
- Engine covers
Do not stop the inspection just because the outside of the harness looks acceptable.
8. Incorrect Previous Repair
Previous repairs may introduce:
- Wrong wire connections
- Excessive solder
- Unsealed crimp connectors
- Incorrect terminal placement
- Signal and ground wires reversed
- Poor-quality extension harnesses
A repair can look neat and still be electrically wrong.
Verify wire colors and terminal positions using the correct wiring diagram.
9. Rodent Damage
Rodents frequently damage wiring near:
- Air boxes
- Battery trays
- Firewall insulation
- Intake manifolds
- Engine covers
Partially chewed wiring may allow conductors to contact grounded components.
Look for:
- Tooth marks
- Nesting material
- Droppings
- Damaged insulation
- Food debris
10. PCM Failure
A failed PCM input circuit is possible but uncommon.
Before replacing the PCM, verify:
- Sensor resistance
- Signal-wire isolation
- Connector condition
- Sensor-ground integrity
- Scan-tool response
- PCM terminal condition
- Applicable software updates
The PCM should be the final suspect, not the opening act.
Unlike P0111, which indicates an implausible or slow sensor reading, P0112 is usually an electrical fault. The PCM is seeing signal voltage that is lower than expected, which it interprets as extremely hot intake air.
The most common causes include a shorted IAT sensor, signal wire shorted to ground, connector corrosion, moisture intrusion, damaged wiring, or a failed integrated MAF/IAT sensor.
Proper diagnosis means confirming the low-voltage condition before replacing parts.
How to Diagnose the P0112 Code
Step 1: Confirm the Code
Connect a professional OBD-II scan tool and record:
- Stored codes
- Pending codes
- Permanent codes
- Freeze-frame data
- Intake Air Temperature
- Engine Coolant Temperature
- Ambient Air Temperature
- Mass Air Flow
- Manifold Absolute Pressure
- Battery voltage
- Fuel trims
- Engine load
Do not clear the code until all diagnostic information has been saved.
The freeze-frame data may reveal whether the fault occurred:
- During a cold start
- While cruising
- Under boost
- Immediately after repairs
- Following an intake modification
Step 2: Check for Related Codes
Inspect for additional codes involving:
- Intake Air Temperature
- Mass Air Flow
- Manifold Absolute Pressure
- Engine Coolant Temperature
- Fuel trims
- Misfires
- Reference voltage
- Sensor grounds
Frequently associated codes include:
- P0095
- P0096
- P0097
- P0098
- P0099
- P0100
- P0101
- P0102
- P0103
- P0104
- P0105
- P0106
- P0107
- P0108
- P0109
- P0110
- P0111
- P0113
- P0114
- P0171
- P0172
- P0300
Several temperature-related codes may indicate a shared wiring or ground problem.
Step 3: Compare Cold-Soak Temperatures
Allow the engine to sit overnight whenever possible.
Before starting the engine compare:
- Intake Air Temperature
- Engine Coolant Temperature
- Ambient Air Temperature
These readings should normally be very close.
Example:
- Ambient: 70°F
- Coolant: 71°F
- IAT: 284°F
That IAT reading clearly indicates a fault.
Cold-soak comparison remains one of the quickest diagnostic tests for P0112.
Step 4: Review Live Data
Monitor the Intake Air Temperature value.
Watch for:
- Fixed high temperature
- Temperature above 250°F
- Reading that never changes
- Sudden drops
- Implausible values
If the sensor reports maximum temperature continuously, suspect:
- Shorted sensor
- Short to ground
- Internal PCM fault
Step 5: Perform a Visual Inspection
Inspect the complete intake system.
Look for:
- Broken connectors
- Pinched wiring
- Melted insulation
- Oil contamination
- Moisture
- Missing seals
- Broken retaining clips
- Previous wiring repairs
Many P0112 faults are discovered before a multimeter is ever connected.
Step 6: Identify the Sensor Type
Determine whether the vehicle uses:
- Stand-alone IAT sensor
- MAF/IAT assembly
- MAP/IAT sensor
- TMAP sensor
This determines:
- Wiring layout
- Expected voltage
- Service procedure
- Replacement options
Always verify the sensor configuration before ordering parts.
Step 7: Inspect the Connector
Disconnect the sensor.
Inspect for:
- Green corrosion
- White corrosion
- Bent pins
- Moisture
- Loose terminals
- Broken locks
- Damaged seals
Corrosion increases electrical problems and may pull the signal toward ground.
Step 8: Verify Terminal Tension
Using the proper terminal tester, verify the connector grips firmly.
Loose terminals can create:
- Voltage drops
- Intermittent shorts
- Repeat failures
- False sensor readings
Avoid using oversized probes that permanently spread connector terminals.
Step 9: Check for Moisture
Inspect for evidence of:
- Rainwater
- Engine washing
- Coolant leaks
- Condensation
- Flood damage
Dry the connector completely before further testing.
Repair damaged seals if moisture is found.
Step 10: Check Live Data While Moving the Harness
Observe Intake Air Temperature while gently moving:
- Sensor connector
- Wiring harness
- Engine harness
- PCM connector
Temperature changes during movement often indicate wiring damage.
Step 11: Disconnect the Sensor
Unplug the sensor.
Many vehicles immediately display an extremely cold reading.
If the scan tool changes from:
280°F → -40°F
the PCM is reacting correctly.
This suggests:
- Wiring is likely intact
- Sensor may be internally shorted
Results vary by manufacturer.
Step 12: Measure Sensor Resistance
Disconnect the sensor.
Measure resistance across the terminals.
Compare resistance with:
- Ambient temperature
- Manufacturer resistance chart
Most NTC sensors should show:
- High resistance when cold
- Lower resistance when warm
A near-zero resistance reading usually indicates a failed sensor.
Step 13: Warm the Sensor
Apply gentle heat.
Watch resistance decrease smoothly.
Sudden drops or fixed resistance indicate sensor failure.
Never use an open flame.
Unlike marshmallows, thermistors do not improve when roasted.
Step 14: Check Signal Voltage
Backprobe the connector.
Measure signal voltage with:
- Ignition ON
- Engine OFF
If voltage remains near zero:
Inspect for:
- Shorted sensor
- Shorted signal wire
- PCM input problem
Always compare with factory specifications.
Step 15: Test for a Short to Ground
Disconnect both sensor and PCM where required.
Check continuity between:
- Signal wire
- Vehicle ground
Continuity where none should exist indicates:
- Wire rubbing metal
- Melted insulation
- Harness damage
Step 16: Check Wiring Continuity
Measure continuity between:
- Sensor connector
- PCM connector
Inspect for:
- Broken conductors
- Corrosion
- Previous repairs
- High resistance
Good continuity alone does not prove the circuit is healthy.
Voltage-drop testing is equally important.
Step 17: Verify Sensor Ground
Inspect the sensor ground.
Perform:
- Voltage-drop test
- Loaded circuit test
Poor grounds may create misleading voltage readings.
Step 18: Inspect MAF/IAT Assembly
If the IAT sensor is integrated into the MAF:
Inspect:
- Sensor housing
- Connector
- Airflow element
- Shared circuits
A healthy MAF airflow reading does not automatically mean the IAT portion is functioning correctly.
Step 19: Inspect Aftermarket Modifications
Check for:
- Cold-air intakes
- Short-ram intakes
- Turbo kits
- Wiring extensions
- Poor crimp repairs
- Incorrect sensor adapters
Many P0112 codes appear shortly after intake installation.
Step 20: Inspect Heat Damage
Check harness routing near:
- Exhaust manifold
- Turbocharger
- Downpipe
- Catalytic converter
- EGR piping
High temperatures frequently melt insulation.
Step 21: Inspect PCM Connector
Inspect PCM connectors for:
- Corrosion
- Bent pins
- Water intrusion
- Loose terminals
Follow manufacturer procedures before disconnecting the PCM.
Step 22: Verify Battery Voltage
Measure:
- Battery voltage
- Charging voltage
- Cranking voltage
Typical charging voltage:
13.5–14.8 volts
Multiple electrical faults should prompt charging-system testing.
Step 23: Check Technical Service Bulletins
Search manufacturer bulletins covering:
- IAT sensors
- MAF sensors
- Wiring revisions
- Software updates
- Intake harness problems
A factory bulletin may eliminate unnecessary repairs.
Step 24: Verify PCM Operation
Only after confirming:
- Sensor
- Wiring
- Grounds
- Connector
- Signal voltage
should PCM diagnosis begin.
PCM failures remain uncommon.
Step 25: Verify the Repair
After repairs:
- Clear all DTCs.
- Cold-soak the vehicle if possible.
- Compare IAT, ECT and ambient temperatures.
- Road test.
- Monitor live data.
- Complete drive cycle.
- Recheck pending codes.
- Confirm P0112 does not return.
Never consider the repair complete until live data behaves normally.
Common Repairs for P0112
Typical repairs include:
- Replace failed IAT sensor
- Replace MAF/IAT assembly
- Repair signal wire
- Repair short to ground
- Replace damaged connector
- Repair melted wiring
- Remove corrosion
- Dry moisture-contaminated connectors
- Replace damaged extension harness
- Repair sensor ground
- Correct aftermarket intake installation
- Update PCM software
- Replace PCM (rare)
P0112 Repair Costs
| Repair | Estimated Cost |
|---|---|
| Diagnostic testing | $100–$200 |
| Connector cleaning | $20–$100 |
| Wiring repair | $100–$500 |
| Separate IAT sensor | $80–$250 |
| MAF/IAT assembly | $150–$650 |
| Intake harness repair | $150–$600 |
| Ground repair | $100–$300 |
| PCM software update | $100–$300 |
| PCM replacement/programming | $1,000–$3,500+ |
A five-dollar corroded connector can imitate a six-hundred-dollar sensor. Testing first is always cheaper than guessing.
Common Diagnostic Mistakes
Replacing the Sensor Immediately
Always verify:
- Wiring
- Voltage
- Ground
- Connector
before replacing the sensor.
Ignoring Cold-Soak Comparison
This quick test often identifies the fault within minutes.
Skipping it wastes valuable diagnostic time.
Assuming the MAF Sensor Is Bad
An integrated sensor may require MAF replacement.
However, confirm the IAT circuit first.
Ignoring Moisture
Water intrusion commonly creates low-voltage faults.
Inspect connector seals carefully.
Overlooking Heat Damage
Harnesses routed near turbochargers and exhaust manifolds frequently develop insulation failures.
Using Incorrect Replacement Sensors
Poor-quality aftermarket thermistors may have incorrect resistance values.
Use quality OEM or premium replacement parts.
Replacing the PCM First
PCM failures are rare.
Complete every electrical test before condemning the control module.
Manufacturer-Specific Notes
General Motors
Inspect:
- MAF/IAT connector
- Shared low-reference circuits
- Air-box wiring
Ford
Check:
- EcoBoost charge-air sensors
- MAF/IAT wiring
- Intake modifications
Toyota / Lexus
Compare:
- Ambient temperature
- Coolant temperature
- Intake temperature
before startup.
Honda / Acura
Inspect:
- Stand-alone IAT sensor
- Connector corrosion
- Intake manifold wiring
Nissan / Infiniti
Check:
- MAF assembly
- Air-box connector
- Harness damage
Hyundai / Kia
Inspect:
- Sensor grounds
- Connector tension
- PCM updates
Volkswagen / Audi
Verify whether the code applies to:
- IAT
- Charge-air sensor
- TMAP sensor
BMW / MINI
Inspect:
- Charge-pipe sensors
- Turbo heat damage
- Oil contamination
Mercedes-Benz
Inspect:
- Combined pressure/temperature sensors
- Wiring exposed to turbocharger heat
Subaru
Inspect:
- MAF/IAT assembly
- Intake modifications
- Filter-oil contamination
Chrysler, Dodge, Jeep and Ram
Inspect:
- Shared grounds
- Intake harness routing
- PCM software updates
Preventative Maintenance
To reduce future P0112 faults:
- Replace air filters regularly.
- Avoid excessive reusable filter oil.
- Keep connectors dry.
- Secure wiring away from heat.
- Repair broken clips.
- Use OEM-quality sensors.
- Inspect wiring after intake work.
- Repair coolant leaks.
- Inspect for rodent damage.
- Avoid unsupported wiring extensions.
Five extra minutes routing a wiring harness properly can prevent hours of electrical diagnosis later.
Frequently Asked Questions
What does P0112 mean?
The PCM has detected an Intake Air Temperature Sensor 1 signal voltage that is lower than expected.
Does P0112 mean the sensor is bad?
Not always.
Possible causes include:
- Shorted sensor
- Shorted wiring
- Connector corrosion
- Moisture
- PCM fault
What scan-tool reading usually accompanies P0112?
An unrealistically high intake-air temperature.
Can I drive with P0112?
Usually for a short period if the engine runs normally.
Avoid driving if:
- Limp mode
- Misfires
- Stalling
- Severe hesitation
- Flashing Check Engine Light
occur.
Can a bad MAF cause P0112?
Yes.
If the IAT sensor is integrated into the MAF housing, internal failure can trigger P0112.
Can moisture cause P0112?
Yes.
Moisture may short the signal to ground.
Can a cold-air intake cause P0112?
Yes.
Improper wiring or connector damage during installation is common.
Can P0112 reduce turbo boost?
Yes.
Many turbocharged engines reduce boost when intake-temperature data is implausible.
How much does P0112 cost to repair?
Repairs range from less than $100 for connector service to $650 for an integrated MAF/IAT assembly. PCM replacement is uncommon but can exceed $3,500.
What is the difference between P0111 and P0112?
P0111 indicates an implausible or slow sensor reading.
P0112 indicates the sensor signal voltage is electrically too low.
Final Thoughts
The P0112 Intake Air Temperature Sensor 1 Circuit Low Input code indicates that the PCM has detected an abnormally low electrical signal from the primary Intake Air Temperature sensor.
The most common causes include:
- Internally shorted IAT sensor
- Signal wire shorted to ground
- Connector corrosion
- Moisture intrusion
- Damaged wiring
- Failed integrated MAF/IAT sensor
The best diagnostic approach begins with a cold-soak comparison, followed by live-data analysis, resistance testing, voltage checks, connector inspection, and wiring verification before replacing any components.
Replacing the PCM should remain the last step after every other electrical possibility has been eliminated.
Related Pro Street Diagnostic Guides
Intake Air Temperature Sensor 1 Codes
- P0110 Code Explained: Intake Air Temperature Sensor 1 Circuit Malfunction
- P0111 Code Explained: Intake Air Temperature Sensor 1 Range/Performance
- P0112 Code Explained: Intake Air Temperature Sensor 1 Circuit Low Input
- P0113 Code Explained: Intake Air Temperature Sensor 1 Circuit High Input
- P0114 Code Explained: Intake Air Temperature Sensor 1 Circuit Intermittent
Intake Air Temperature Sensor 2 Codes
- P0095 Code Explained: Intake Air Temperature Sensor 2 Circuit
- P0096 Code Explained: Intake Air Temperature Sensor 2 Range/Performance
- P0097 Code Explained: Intake Air Temperature Sensor 2 Circuit Low
- P0098 Code Explained: Intake Air Temperature Sensor 2 Circuit High
- P0099 Code Explained: Intake Air Temperature Sensor 2 Circuit Intermittent
Related Air-Metering Codes
- P0100 Code Explained: Mass Air Flow Sensor Circuit Malfunction
- P0101 Code Explained: Mass Air Flow Sensor Range/Performance
- P0102 Code Explained: Mass Air Flow Sensor Circuit Low Input
- P0103 Code Explained: Mass Air Flow Sensor Circuit High Input
- P0104 Code Explained: Mass Air Flow Sensor Circuit Intermittent
- P0105 Code Explained: MAP/Barometric Pressure Circuit Malfunction
- P0106 Code Explained: MAP/Barometric Pressure Circuit Range/Performance
- P0107 Code Explained: MAP/Barometric Pressure Circuit Low Input
- P0108 Code Explained: MAP/Barometric Pressure Circuit High Input
- P0109 Code Explained: MAP/Barometric Pressure Circuit Intermittent
Complete OBD-II Code Libraries
- https://my.prostreetonline.com/dtc-doctor/b-code-obd-ii-codes/
- https://my.prostreetonline.com/dtc-doctor/c-code-obd-ii-codes/
For the strongest topical authority, interlink this article with P0110–P0114, the P0095–P0099 Intake Air Temperature Sensor 2 series, and the P0100–P0109 Mass Air Flow and MAP sensor guides.
