The P0393 OBD-II trouble code means the powertrain control module has detected voltage above the expected range in the Camshaft Position Sensor “B” circuit on Bank 2.
On a Hall-effect sensor, the signal may remain stuck at its high-voltage state instead of switching normally as the camshaft rotates. Common causes include a signal wire shorted to voltage, an open sensor ground, an open signal circuit held high by the PCM, connector contamination or a sensor that can no longer pull the signal low.
P0393 does not automatically prove the camshaft-position sensor has failed. The sensor’s power supply, ground, signal wire, connector and PCM input all require testing.
Sensor B commonly monitors the exhaust camshaft on a DOHC engine, but manufacturers can define it differently. Bank 2 is the cylinder bank that does not contain cylinder number one. Confirm both before testing, unless replacing the wrong camshaft sensor sounds like a particularly inefficient weekend project.
P0393 Quick Reference
| Item | Details |
|---|---|
| Trouble code | P0393 |
| Code definition | Camshaft Position Sensor “B” Circuit High Input Bank 2 |
| System affected | Bank 2 camshaft-position monitoring |
| Likely sensor | Usually the Bank 2 exhaust camshaft sensor |
| Fault type | Sensor B signal voltage above the expected range |
| Common causes | Short to voltage, open ground, failed sensor, damaged connector or PCM input fault |
| Common symptoms | Check Engine Light, hard starting, rough running, hesitation or reduced power |
| Typical severity | Moderate |
| Safe to drive? | Possibly for a short distance if the engine runs normally |
| Repair difficulty | Intermediate electrical diagnosis |
What Does the P0393 Code Mean?
P0393 indicates that the Bank 2 Camshaft Position Sensor B signal remains above the voltage range expected by the PCM.
The PCM expects the sensor waveform to switch or alternate as the camshaft trigger wheel rotates. If the signal remains high, cannot transition low or exceeds its normal voltage range, the PCM may store P0393.
Depending on circuit design, the PCM may detect:
- Signal continuously stuck high
- Voltage above the expected signal range
- Missing low-side transitions
- Signal shorted to reference voltage
- Signal shorted to battery voltage
- Open sensor ground
- Failed sensor pull-down circuit
- Open signal wire held high by an internal PCM pull-up
- PCM input-circuit fault
P0393 describes the electrical condition detected by the PCM. It does not identify which component caused it.
What Does Sensor B Mean?
On many dual-overhead-cam engines:
- Sensor A monitors the intake camshaft
- Sensor B monitors the exhaust camshaft
This convention is common but not universal.
Before diagnosis, confirm:
- Whether Sensor B monitors the intake or exhaust camshaft
- Its exact physical location
- Connector pinout
- Sensor type
- Supply-voltage specification
- Ground circuit
- Expected waveform
The manufacturer’s service information should make the final determination.
What Does Bank 2 Mean?
Bank 2 is the cylinder bank that does not contain cylinder number one.
Bank 2 is not universally the driver side, passenger side, front bank or rear bank. Its physical location depends on engine design.
P0393 normally applies to V-type or opposed engines with two cylinder banks. Inline engines generally have only Bank 1.
Use the cylinder-numbering diagram or firing-order information to identify Bank 2 accurately.
How the Camshaft-Position Sensor Works
The camshaft-position sensor monitors a toothed, slotted or magnetized trigger wheel attached to the camshaft, actuator or phaser.
As the camshaft rotates, the sensor generates a waveform. The PCM uses this signal to determine:
- Camshaft position
- Cylinder identification
- Sequential fuel-injection timing
- Ignition timing
- Variable-valve-timing operation
- Startup synchronization
- Misfire-monitoring accuracy
- Camshaft-to-crankshaft relationship
Two common sensor designs are used.
Hall-Effect Camshaft Sensor
A Hall-effect sensor normally has three circuits:
- Power or reference voltage
- Sensor ground
- Digital signal output
The signal switches between defined high and low voltage states as the trigger wheel passes the sensor.
A circuit-high condition may occur when:
- The signal is shorted to the supply circuit
- The signal is shorted to battery voltage
- The sensor ground is open
- The sensor cannot switch its output low
- The signal wire is open and held high by a PCM pull-up
- The PCM input is defective
Magnetic Camshaft Sensor
A magnetic or variable-reluctance sensor commonly has two wires and generates an alternating-current waveform.
Its voltage increases with camshaft speed. A manufacturer may interpret excessive amplitude, incorrect circuit bias or introduced external voltage as a high-input condition.
The correct voltage test depends on the actual sensor and PCM circuit. Do not apply Hall-effect specifications to a magnetic sensor because both components happen to live near a camshaft.
Symptoms of a P0393 Code
Possible symptoms include:
- Illuminated Check Engine Light
- Extended cranking
- Hard starting
- Engine cranks but does not start
- Rough idle
- Engine hesitation
- Reduced power
- Poor throttle response
- Misfire-like operation
- Increased fuel consumption
- Engine stalling
- Variable valve timing disabled
- Limp-home mode
- Difficult hot or cold starting
- No noticeable symptoms beyond the warning light
Some PCMs can continue operating using other camshaft sensors and the crankshaft-position signal. The engine may run under a backup strategy while variable valve timing is disabled.
If the starter turns the engine normally but it refuses to run, use the engine cranks but won’t start diagnostic guide to check spark, injector command, fuel pressure and engine synchronization.
Common Causes of P0393
Potential causes include:
- Signal Wire Shorted to Reference VoltageDamaged insulation may allow the signal circuit to contact the sensor-supply wire.
- Signal Wire Shorted to Battery VoltageThe Sensor B signal may contact an ignition or battery-positive circuit.
- Open Sensor GroundA Hall-effect sensor may remain at its high output state when its ground connection is lost.
- High Resistance in the Sensor GroundCorroded or loose terminals can prevent the sensor from pulling its output to the expected low state.
- Failed Bank 2 Camshaft Position Sensor BInternal electronics may hold the signal high or prevent normal switching.
- Open Signal WireIf the PCM uses an internal pull-up resistor, an open signal wire may remain at a high voltage.
- Oil-Contaminated ConnectorEngine oil may bridge the signal terminal to the sensor-supply circuit or interfere with terminal contact.
- Water IntrusionMoisture and corrosion can cross-connect adjacent terminals.
- Bent or Spread Connector TerminalPoor contact can leave the signal electrically floating or interrupt the sensor ground.
- Damaged Wiring HarnessWiring near the cylinder head may become melted, pinched or rubbed against a powered circuit.
- Improper Aftermarket WiringRemote-start equipment, piggyback computers or prior harness repairs can introduce voltage into the signal circuit.
- Incorrect Replacement SensorA sensor with the wrong electrical design may not produce the voltage pattern expected by the PCM.
- Charging-System OvervoltageExcessive charging voltage may affect sensor and PCM circuits, usually while producing other high-input codes.
- Poor PCM GroundA shifted PCM ground reference can make sensor voltage appear higher than expected.
- PCM Input-Circuit FailureAn internal PCM fault may hold the Bank 2 Sensor B input high or interpret the signal incorrectly.
- Incorrect Sensor-to-Trigger RelationshipA Hall-effect sensor may remain in one state if the trigger is damaged or outside the sensing range, although this more commonly causes performance-related codes.
How Serious Is P0393?
P0393 is normally a moderate-severity trouble code.
The vehicle may continue running if the PCM can use another camshaft-position input, but it may experience:
- Extended cranking
- Reduced power
- Rough running
- Poor fuel economy
- Disabled variable valve timing
- Intermittent stalling
- A no-start condition
Diagnosis should be scheduled promptly.
Do not continue driving if the engine stalls, misfires severely, loses substantial power or displays a flashing Check Engine Light.
P0390 Through P0393 Compared
These codes affect the same Bank 2 Sensor B circuit but identify different fault conditions.
| Code | Definition | Primary diagnostic focus |
| P0390 | Sensor B Circuit Malfunction Bank 2 | General electrical failure or unusable signal |
| P0391 | Sensor B Circuit Range/Performance Bank 2 | Implausible waveform, timing or response |
| P0392 | Sensor B Circuit Low Input Bank 2 | Signal voltage below the expected range |
| P0393 | Sensor B Circuit High Input Bank 2 | Signal voltage above the expected range |
P0393 should remain focused on the high-voltage condition rather than general sensor failure or camshaft timing.
P0393 vs. P0348
P0348 is the corresponding high-input code for Camshaft Position Sensor A on Bank 2.
| Code | Bank | Sensor | Fault |
| P0348 | 2 | Sensor A | Circuit high input |
| P0393 | 2 | Sensor B | Circuit high input |
On many DOHC engines, P0348 applies to the Bank 2 intake camshaft sensor while P0393 applies to the Bank 2 exhaust camshaft sensor.
P0393 vs. P0368
P0368 applies to Sensor B on Bank 1.
| Code | Bank | Sensor | Fault |
| P0368 | 1 | Sensor B | Circuit high input |
| P0393 | 2 | Sensor B | Circuit high input |
If both codes appear together, inspect shared sensor grounds, PCM grounds, system voltage and reference circuits before replacing both sensors.
P0393 vs. P0394
P0393 indicates a signal that remains consistently above its expected voltage range.
P0394 indicates that the Bank 2 Sensor B signal becomes intermittent or temporarily disappears.
A damaged connector can cause either code, but P0393 should own the stuck-high and excessive-voltage search intent.
How to Diagnose the P0393 Code
The correct procedure begins with identifying the sensor design and expected voltage range.
1. Confirm P0393
Connect a capable scan tool and record:
- P0393
- Current, pending and history codes
- Freeze-frame information
- Engine RPM
- Battery voltage
- Engine coolant temperature
- Vehicle speed
- Engine load
- Camshaft synchronization
- Crankshaft synchronization
- Bank 2 Sensor B position data
- VVT command data
Do not clear the code before recording its freeze-frame conditions.
2. Check for Related Codes
Look for codes involving:
- P0390 through P0394
- Bank 2 Sensor A
- Bank 1 Sensor B
- Crankshaft-position sensors
- Sensor reference voltage
- System overvoltage
- PCM grounds
- Module communication
- Camshaft correlation
Several circuit-high codes appearing together suggest a shared ground, charging-system or PCM problem.
3. Identify Bank 2 and Sensor B
Use factory service information to confirm:
- Cylinder number-one location
- Bank 2 location
- Sensor B location
- Intake or exhaust designation
- Sensor type
- Supply voltage
- Ground circuit
- Signal range
- PCM connector terminals
Do not test a sensor based only on which connector is easiest to reach.
4. Inspect the Sensor and Connector
Switch the ignition off and inspect:
- Connector lock
- Terminal tension
- Bent or pushed-back pins
- Oil contamination
- Water intrusion
- Corrosion
- Damaged seals
- Cracked connector housing
- Incorrect sensor installation
Oil inside the connector can bridge adjacent terminals. Clean the connector and locate the source of the contamination.
5. Inspect the Wiring Harness
Follow the Bank 2 Sensor B wiring toward the PCM.
Look for:
- Signal wiring rubbed against a supply circuit
- Melted insulation
- Harness contact with exhaust components
- Pinched wiring beneath covers or brackets
- Improper splices
- Aftermarket wiring
- Oil-soaked loom
- Stretched conductors
- Damage from previous engine repairs
Pay particular attention to sections where powered and signal wires run together.
6. Check Battery and Charging Voltage
Measure:
- Battery voltage with the engine off
- Minimum cranking voltage
- Charging voltage at idle
- Charging voltage under electrical load
- Alternator ripple
- Engine and PCM ground voltage drop
An overcharging alternator can raise circuit voltage and may generate multiple high-input codes.
Correct charging-system faults before continuing with sensor diagnosis.
7. Verify Sensor Supply Voltage
For a Hall-effect sensor, confirm the specified supply voltage.
The sensor may use:
- Five volts
- Eight volts
- Battery voltage
- Another regulated supply
Do not assume that a measured five volts is correct simply because five volts is common. Compare the reading with service information.
8. Test Sensor Ground
Back-probe the ground circuit and perform a voltage-drop test while the sensor is operating.
An open or high-resistance ground may prevent the sensor from switching its output low.
Inspect:
- Sensor ground terminal
- Shared ground splice
- Cylinder-head grounds
- Engine-to-body ground straps
- PCM grounds
Repair any excessive voltage drop before replacing the sensor.
9. Measure the Sensor B Signal
Use a high-impedance digital multimeter or oscilloscope.
During cranking or engine operation, a Hall-effect signal should switch between its specified high and low states.
A P0393 waveform may show:
- Signal continuously at its supply voltage
- Signal continuously near battery voltage
- No low-side transitions
- Low state that remains above specification
- Voltage exceeding the circuit’s normal high state
- Signal remaining high with the sensor disconnected
A multimeter may average a switching signal and hide brief transitions. An oscilloscope is the preferred tool.
10. Check for a Short to Voltage
Disconnect the sensor and PCM according to the manufacturer’s procedure.
Test the isolated signal circuit for continuity to:
- Sensor-supply voltage
- Ignition voltage
- Battery-positive wiring
- Adjacent powered sensor circuits
- VVT solenoid wiring
- Alternator wiring
Move the harness while observing the meter.
Do not measure resistance on a powered circuit.
11. Check for an Open Sensor Ground
If the signal remains high with the sensor connected, verify ground integrity under load.
Do not ground the circuit blindly. Follow the manufacturer’s procedure and use an approved fused jumper only when specified.
Grounding the wrong PCM circuit can turn a manageable sensor code into a module-programming appointment.
12. Isolate the Sensor
Observe signal voltage with Sensor B connected and disconnected.
Possible results include:
- Voltage returns to normal with sensor disconnected: internally failed sensor
- Voltage remains excessively high with sensor disconnected: wiring short or PCM input bias
- Signal changes when an approved ground is restored: ground-circuit fault
- Voltage is normal at sensor but high at PCM: harness or connector problem
Interpret disconnected voltage using the wiring diagram. An internal PCM pull-up can make an open signal wire read high by design.
13. Compare Bank 1 and Bank 2 Sensor B
Use a multi-channel oscilloscope to compare both banks.
Compare:
- High-state voltage
- Low-state voltage
- Pulse shape
- Signal timing
- Response to engine speed
- Waveform stability
If Bank 1 operates normally while Bank 2 remains high, concentrate on the Bank 2 sensor and circuit.
If both remain high, investigate shared grounds, system voltage and PCM operation.
14. Compare the Signal at the Sensor and PCM
Measure Bank 2 Sensor B at its connector and then at the PCM.
Possible findings include:
- High at both locations: sensor, ground or wiring short
- Normal at sensor but high at PCM: harness cross-short or connector problem
- Correct waveform at PCM but incorrect scan data: PCM input or software problem
- Signal changes when the PCM connector moves: terminal damage
Testing both ends prevents the sensor from being blamed for a signal altered elsewhere in the circuit.
15. Inspect the Trigger and Sensor Air Gap
P0393 is primarily an electrical high-input code, but inspect the physical trigger if the circuit tests correctly.
Check for:
- Incorrect sensor installation
- Excessive sensor air gap
- Missing trigger feature
- Damaged reluctor
- Shifted trigger wheel
- Camshaft end play
- Wrong replacement sensor
Some active sensors may remain in one state if the trigger does not pass through the expected sensing range.
16. Perform a Heat and Wiggle Test
If P0393 is intermittent:
- Monitor the waveform during warm-up
- Move the harness carefully
- Manipulate the connector
- Apply controlled heat according to service procedures
- Cool the sensor and repeat the test
A sensor may fail internally when hot, while damaged insulation may contact a powered circuit only as the harness moves.
17. Keep Mechanical Timing in Its Lane
P0393 identifies excessive circuit voltage. It is not primarily a camshaft-timing code.
Investigate timing chains, phasers and VVT operation only when:
- The electrical waveform switches correctly
- Correlation or timing codes accompany P0393
- Abnormal mechanical noise is present
- Recent timing repairs were performed
A stretched chain does not normally short a sensor signal to five volts, despite timing components occasionally being blamed for nearly everything.
18. Check the PCM Last
Consider PCM failure only after confirming:
- Correct Bank 2 identification
- Correct Sensor B identification
- Correct sensor supply voltage
- Reliable sensor ground
- No signal short to voltage
- Proper signal continuity
- Correct sensor installation
- Good charging-system voltage
- Valid waveform at the PCM
- No applicable software update
PCM replacement may require programming, security initialization and camshaft or crankshaft relearn procedures.
Common P0393 Diagnostic Mistakes
Avoid these common mistakes:
- Testing Sensor A instead of Sensor B
- Testing Bank 1 instead of Bank 2
- Assuming Sensor B always means exhaust
- Replacing the sensor without checking its ground
- Ignoring a signal wire shorted to reference voltage
- Assuming an open signal wire must measure zero volts
- Overlooking an internal PCM pull-up
- Ignoring charging-system overvoltage
- Using a conventional test light on the signal circuit
- Grounding PCM circuits without service information
- Damaging terminals with oversized probes
- Replacing timing components for a circuit-high code
- Replacing the PCM before isolating the harness
Repairs That May Fix P0393
Possible repairs include:
- Replacing Bank 2 Camshaft Position Sensor B
- Repairing a signal wire shorted to reference voltage
- Repairing a signal wire shorted to battery voltage
- Repairing an open sensor ground
- Repairing a high-resistance sensor ground
- Cleaning oil or corrosion from the connector
- Replacing damaged terminals
- Replacing a broken connector
- Repairing an open signal circuit
- Correcting aftermarket wiring
- Installing the correct replacement sensor
- Repairing charging-system overvoltage
- Correcting sensor installation
- Repairing a damaged trigger wheel
- Updating PCM software
- Replacing and programming the PCM after confirmed failure
Estimated P0393 Repair Costs
Actual costs depend on the vehicle and root cause.
| Repair | Estimated cost |
| Diagnostic inspection | $100–$250 |
| Connector or terminal repair | $100–$400 |
| Camshaft Position Sensor B replacement | $180–$550 |
| Sensor-ground repair | $120–$450 |
| Charging-system repair | $200–$1,100 |
| Major harness repair | $350–$1,200 |
| Camshaft-reluctor repair | $600–$2,000 |
| PCM software update | $100–$300 |
| PCM replacement and programming | $800–$2,500 |
The sensor itself may be affordable. Finding a signal wire fused to a powered conductor deep inside a wrapped engine harness is where the diagnostic invoice begins doing cardio.
Can You Drive With P0393?
You may be able to drive a short distance if the engine starts, runs smoothly and does not stall.
Do not continue driving if:
- Starting becomes unreliable
- The engine stalls
- Power drops substantially
- The engine misfires heavily
- The Check Engine Light flashes
- Multiple sensor-high codes appear
- Wiring becomes hot or produces an electrical odor
Review what the Check Engine Light means for additional warning-light guidance.
How to Verify the Repair
After completing the repair:
- Reconnect every sensor and module.
- Confirm connector-terminal engagement.
- Secure the harness away from heat and moving components.
- Verify charging-system voltage.
- Clear current and pending trouble codes.
- Monitor Bank 2 Sensor B during cranking.
- Verify the signal switches between its correct high and low states.
- Compare Bank 1 and Bank 2 Sensor B waveforms.
- Warm the engine fully.
- Repeat the harness wiggle test.
- Recreate the freeze-frame conditions.
- Complete the required drive cycle.
- Perform any manufacturer-specified relearn.
- Check for pending codes.
The repair is confirmed when Bank 2 Sensor B voltage remains within specification, its waveform switches normally and P0393 does not return.
Frequently Asked Questions
What does the P0393 code mean?
P0393 means the PCM detected voltage above the expected range in the Bank 2 Camshaft Position Sensor B circuit.
Is Sensor B the exhaust camshaft sensor?
Sensor B commonly monitors the exhaust camshaft on a DOHC engine, but the manufacturer’s service information should confirm it.
Which side is Bank 2?
Bank 2 is the cylinder bank that does not contain cylinder number one. Its physical location varies by engine.
Does P0393 mean the camshaft sensor is bad?
Not necessarily. A signal shorted to voltage, open sensor ground, damaged connector or PCM input problem can produce the same code.
What is the difference between P0392 and P0393?
P0392 means the Sensor B signal is too low. P0393 means the Sensor B signal is too high.
What is the difference between P0348 and P0393?
P0348 applies to Sensor A on Bank 2. P0393 applies to Sensor B on Bank 2.
What is the difference between P0368 and P0393?
P0368 applies to Sensor B on Bank 1. P0393 applies to Sensor B on Bank 2.
Can an open sensor ground cause P0393?
Yes. A Hall-effect sensor may remain at its high signal state if its ground circuit is open or has excessive resistance.
Can an open signal wire cause P0393?
Yes. A PCM with an internal pull-up resistor may hold an open signal circuit at a high voltage.
How do you diagnose P0393?
Identify Bank 2 Sensor B, verify its supply and ground, inspect the waveform and isolate the signal circuit to test for a short to voltage.
Final Thoughts
P0393 means the Bank 2 Camshaft Position Sensor B circuit is electrically higher than the PCM expects.
Begin by identifying the correct sensor and cylinder bank. Inspect the connector, verify sensor ground and check the signal wire for contact with reference or battery voltage. Use an oscilloscope to determine whether the signal switches normally or remains stuck high.
The sensor may ultimately require replacement, but testing the full circuit first will separate sensor failure from an open ground, damaged harness or PCM input problem without volunteering for unnecessary parts replacement.
Visit the OBD-II Doctor for additional diagnostic guides or browse the complete P-series OBD-II code reference to identify related powertrain faults.