Code 12 display — No RPM reference pulse detected

What does Code 12 mean?

Code 12 means the engine control module (ECM) is not receiving a signal indicating the engine's rotational speed. This is often expected when the engine is not running, but if displayed during a test with the engine off, it indicates a problem.

• Engine is not running when it should be
• Problem with the crank sensor or its wiring
• Issue with the ECM or check engine light circuitry

Click steps to track your progress.

1. 1

   Ensure the engine is running as expected for the test being performed.

2. 2

   Verify the scan tool connection to the vehicle.

3. 3

   If performing a Field Service test with the ignition on but engine off, Code 12 is normal.

4. 4

   If Code 12 appears when the engine is running, check the crank sensor and its wiring.

5. 5

   If the issue persists, there may be a problem with the PCM or the check engine light circuit.