Error Code 12231
- The check engine light is off. There is no RPM signal. This code will always be present if the test is run with the engine off. Crank engine for 5 seconds. If code disappears, the RPM signal is OK. If code does not disappear, go to step 2).
- Check fuse no. 3. Check the ignition system input at pin 1 of the LH control unit.