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 (PCM)
The PCM is on the high speed CAN. The PCM controls the engine for better fuel economy, emissions control, failure mode detection and storage, and all passive anti-theft system (PATS) functions. If one of the bus wires becomes shorted to ground or voltage, communications can continue at a reduced level. Check the high speed CAN circuits 1908 (WH) and 1909 (BK), between the PCM C175b and the DLC C251. Total resistance values must not be more than 5 ohms. If the resistance is more than 5 ohms, there is an open circuit in the high speed CAN, damage to the DLC C251, damage to the PCM C175b, or a problem in the in-line connector. Since both the PCM and the instrument cluster share network termination responsibilities, a problem in either of these modules can result in a high speed CAN failure. For additional PATS information, refer to ANTI-THEFT - PATS . For additional PCM information, refer to the INTRODUCTION - GASOLINE article. For removal and installation information, refer to ELECTRONIC ENGINE CONTROLS - 2.3L or ELECTRONIC ENGINE CONTROLS - 3.0L (4V) .
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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.