The PCM supplies a buffered (reference) voltage to the various information sensors and switches. The PCM monitors the input components for circuit continuity and out-of-range values. The PCM also provides performance checking. Performance checking refers to the PCM indicating a fault when the signal from an input does not seem reasonable, i.e., a Throttle Position (TP) sensor that indicates a high throttle position at low engine loads or low manifold absolute pressure sensor voltage. The input components may include, but are not limited to the following sensors and switches:

A/C Compressor Control Module (A/C Relay)
Camshaft Position (CMP) Sensor
Clutch Pedal Position (CPP) Switch
Crankshaft Position (CKP) Sensor
Electrical Load Idle-Up Signal
Engine Coolant Temperature (ECT) sensor. In addition to circuit continuity and rationality check, ECT sensor is monitored to ensure its ability to maintain a constant temperature, enabling closed loop fuel control.
Fuel Level Sensor
Fuel Tank Pressure (FTP) Sensor
Heated Oxygen Sensor (HO2S)
Knock (KS) Sensor
Mass Airflow (MAF) Sensor
Power Steering Pressure (PSP) Switch
Throttle Position (TP) Sensor
Transaxle Range (TR) Switch
Vehicle Speed Sensor (VSS)

Vehicles are equipped with different combinations of input devices. Not all devices are used on all models. To determine input device usage on a specific model, see WIRING DIAGRAMS article.

When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

• You smell fuel, burning insulation, or see smoke.

• Brakes feel soft, pull hard to one side, or make grinding noises.

• The engine overheats, stalls repeatedly, or misfires under load.

• You are missing required tools, torque specs, or safe lifting equipment.

• You are not confident in the next step or safety outcome.

Safety Warning

Input Devices: Notes

Use the Manual With the Right Hardware

When to See a Mechanic