This is a very common question we get from many customers who want to build their own street rod or wish to get a little more serious with their LS1 swap, but want to do it themselves. Unfortunately many people get caught up in the power to weight ratio gain that obviously be found by swapping a GEN III block into a lightweight car. The idea of swapping a motor found in a nearly 5000 lb F body into something in the mid 2000’s is a huge difference after all.

Sadly most of these people jump right into the swap without really taking the time to build a checklist and ensure their swap goes as smoothly as possible. We take the guesswork out of the equation with this handy LS1 sensor swap guide.

PCM Sensors

Coolant Temperature Sensor

This sensor informs the PCM whether or not the engine has reached or exceeded the operating temperature value. It utilizes a very wide range of functions, from informing the PCM when to use the startup enrichment mode (SEM) and of course when to turn on the cooling fans.

This sensor is also the one that operates the dashboard coolant temperature gauge, and is necessary to operate and run the motor in whatever swap you are putting it in.

This sensor is a 2 pin unit found in the driver side cylinder head and is connected with a standard GM weatherproof connector.

Idle Air Control Valve :

This isn’t a sensor in the true sense of the word, but this unit is vital to the operation of your GEN III motorswap.

The PCM controls the idle of the motor using this valve by opening the unit and allowing more air into the intake manifold and past the throttle body. To decrease RPM, the PCM will close this unit more to reduce the amount of air that passes by the throttle body.

The Idle Air Control Valve (IAC) is part number 17113391 and is found in the throttle body, and is connected with a 4 pin GM weatherproof connector.

Cam Position Sensor :

The camshaft position (CMP) sensor picks up it’s signal through the reluctor wheel which is at the rear of the camshaft itself. This sensor informs the PCM whether a cylinder is on the firing or the exhaust stroke, as the motor is turning the reluctor wheel interrupts the hall effect sensor by blocking the magnetic field the sensor emits.

This sensor is mounted at the rear of the engine and thorough the top of the engine block – GM Part Number 12561211. 

Crank Position Sensor :

This sensor provides the PCM with the data needed to determine engine speed and one of the main factors used to calculate injector pulse width (IPW) and ignition timing. Using a similar hall effect style of operation, another reluctor wheel  interrupts the signal in the sensor giving the PCM the data it needs.

This sensor is located above the starter at the rear of the block on the passenger side – GM Part Number 12 560 228

Air Intake Temperature Sensor :

The PCM uses this data to primarily alter where on the fuel and timing map it wishes to operate, and along with MAS it ensures your GEN III motorswap is running at optimum condition

This sensor is located in the intake tract, usually on the airbox or near the mass airflow sensor ( MAS ) and is part number 12110319 or 12160244.

Knock Sensor :

There are 2 of these sensors located on your LS1 and they are designed to detect the high-frequency vibrations and sounds caused by predetonation and knock.

By incorporating 2 sensors it allows the PCM more of a safety window in which to operate the vehicle at peak performance while maintaining a safe air/fuel mixture. These knock sensors are located beneath the intake manifold on the engine valley cover and can be accessed rather easily for service.

These sensors are part number 12589867 and are connected through a special connector that is insulated with a large weatherproof grommet to help protect the sensor and connector from the elements.

Mass Airflow Sensor :

The Mass Air Flow Sensor ( MAS ) is a vital part of your motorswap and is also something that is commonly upgraded using a Granatelli or SLP for potential power gains.

The MAS delivers necessary information to the PCM to deliver the correct fuel for the metered air entering the engine. The intake of air changes density as it expands and contracts with atmospheric pressure and temperatures. Some values the MAS measures and records is air temperature, altitude, volumetric flow and barometric pressure that the PCM interprets to determine the quantity of intake air in each piston stroke.

Many different part numbers exist for this application, especially if you are swapping in a different motor than just a LS1, part number 19207203 is the most common one. The MAS is a very easy part to recognize and is located in the intake tract before the throttle plate, connected by a 5 or 6 pin weatherproof connector.

Click here to learn How To Test a LS1 MAS

Manifold Absolute Pressure Sensor :

This sensor measures the pressure of the air in the intake manifold, which tells the PCM how much air is entering the engine and how pressurized the air is.

This unit is commonly damaged on many swaps we receive here, as its located near the rear of the intake manifold and is mounted in a way that many people either snap or break the snap clips on the connectors.

The Manifold Absolute Pressure Sensor ( MAP ) is GM part number 12614970 and is mounted on a special mount with barbed prong air ports.

Check here to learn How To Test a LS1 MAP Sensor.

Throttle Position Sensor :

This TPS sensor provides vital information to the PCM in relation to the throttle valve position, which in turn dictates how much air will be entering the engine. While F body vehicles have this sensor mounted on the throttle body, Corvettes have this sensor incorporated into the gas pedal assembly inside the cabin.

The TPS is a very commonly swapped engine part, especially for those getting their swaps from Corvettes. If you haven’t already, check out our LS1 Throttle Body Modification that allows for 100% Wide Open Throttle (WOT) operation. The TPS part number is 17123852

The Vehicle Speed Sensor (VSS) monitors road speed for cruise control, speedometer readings and fuel trims. This sensor is located inside the transmission.

Oxygen Sensors :

The Oxygen Sensors ( 02 Sensors ) are the PCM’s eyes and ears, allowing it to see just how rich or lean your engine is running. There are 4 located that you will need for your swap, the 2 front upstream 02 sensors relay vital air fuel mixture information to the PCM, while the downstream units dictate catalytic converter performance.

You may or may not want to swap in 02 eliminators for your downstream units, as they are not needed for engine operation or if you are running your vehicle off-road and do not have catalytic converters. The part numbers are as follows ; 19178928, Front left 02 sensor, 19178924, Front Right 02 Sensor

Oil Pressure Sensor :

The Oil Pressure Sensor monitors engine oil pressure and has the capability to shut down the motor if the PCM sees values that it doesn’t like. This sensor also supplies information to the dashboard oil pressure gauge and is not to be confused with the oil temperature gauge which on Corvette motors is found in the oil pan.

This sensor is located behind the intake manifold at the rear of the block near the camshaft position sensor. Because of it’s placement and height, this is another sensor that is commonly broken or damaged for many engine swap candidates. This sensor is part number 12562267

This is a complete breakdown of sensors and part numbers you will need for your engine swap, if you need further tech or further explanation to the acronyms found on this writeup please return to our LS1 engine swap guide.

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Happy motor swapping!