Engine RPM Output Circuit Malfunction
The P0654 code indicates a malfunction in the engine RPM output circuit, which is responsible for sending the engine speed signal to other modules (e.g., transmission control module, instrument cluster). This circuit typically involves a dedicated wire from the PCM to other modules. When the PCM detects an abnormal voltage or signal on this circuit, it sets this code. Common causes include a short to ground or voltage, open circuit, or faulty PCM.
01. Most Common Causes
- Short to ground or voltage in the RPM output circuit
- Open circuit or high resistance in the RPM output wire
- Faulty PCM (rare)
02. Symptoms You Will Notice
- Check Engine Light illuminated
- Erratic or no tachometer reading
- Transmission shifting issues (if transmission relies on RPM signal)
- Possible stalling or poor engine performance
03. Step-by-Step Diagnosis
Step 1: Use a scan tool to verify the code and check for related codes.
Step 2: Inspect the RPM output circuit wiring for damage, corrosion, or loose connections.
Step 3: Test the circuit for shorts to ground or voltage using a multimeter.
Step 4: Check continuity of the RPM output wire from PCM to the destination module.
Step 5: If wiring is intact, test the PCM output signal with an oscilloscope or scan tool data.
Step 6: Replace the PCM if all wiring and signals are normal (rare).
04. Commonly Affected Makes
05. Frequently Asked Questions
Is it safe to drive with this code?▼
It is generally not recommended to drive long distances as the issue can cause transmission problems or stalling. Short trips may be possible, but have it diagnosed promptly.
How much does it cost to fix?▼
The cost typically ranges from $50 to $150 for diagnosis and repair, but can be higher if the PCM needs replacement.