Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Powertrain Control Module
The Powertrain Control Module (PCM) is located in the engine compartment. The PCM is the control center of the vehicle that controls the following:
- Fuel metering system.
- Transmission shifting.
- Ignition timing.
- On-board diagnostics for powertrain functions.
The PCM supplies either 5 or 12 volts to power various sensors and switches. This is done through resistances in the PCM. The resistance is so high in value that a test light does not illuminate when connected to the circuit. In some cases, even an ordinary shop voltmeter does not give an accurate reading because the voltmeter's resistance is too low. Therefore, a DVOM with a minimum of 10 megohms input impedance is required to ensure accurate voltage readings.
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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.