All Updated Information
The Code 41 flow chart has been updated as per the General Motors Technical Service Bulletin (TSB) listed below. All outdated information has been discarded.
- Buick 91-6E-13
- Oldsmobile 91-T-45
Code 41 will set if the engine is running and a cam sensor signal is not received by the ECM for the last 2-5 seconds.
NOTE:
Test numbers refer to test numbers on diagnostic chart.
- Verifies proper operation of circuits No. 633, 644 and 645.
- Tests circuit No. 630 from the C(3)I ignition module to the ECM.
- If harmonic balancer windows are interfacing with the cam sensor, the voltage reading may be zero. Bumping the engine with the starter will cause the condition to go away.
- If voltage reading is varying around a midpoint of 10.5 volts and connections are good, the ECM is faulty.