How to Test a GM 3.6L Timing Chain
- Set up your labscope to scope 3 channels at a time. Attach a back probe to each lead and make sure your scope is grounded properly
- Locate the two bank 1 camshaft position sensors and crankshaft position sensor, back probe the middle wire of each sensor to acquire a signal Watch
- Unplug VVT solenoid connectors to ensure engine is in base timing
Tip : It may be difficult to access crankshaft position sensor connector on AWD vehicles, an alternative connection at ECM connector may be necessary
- Adjust your labscope software to get a useable pattern, recommended settings (0-10V scale, 20m/dv time base). Watch
- Label channels with their corresponding sensors to aid in waveform analysis Watch
- Pause the waveform and zoom in on one full engine cycle or two crankshaft revolutions. This will make it easier read waveform and to check the cam/crank timing Watch
- Check pattern of bank 1 intake camshaft position sensor signal, compare with known good pattern Watch
- Check pattern of bank 1 exhaust camshaft position sensor signal, compare with known good pattern Watch
- Locate the two bank 2 camshaft position sensors. Back probe the middle wire of each sensor connector to acquire a signal Watch
- Acquire waveform using same voltage and time scale and zoom in on one full engine cycle or two crankshaft revolutions. Watch
- Check pattern of bank 2 intake camshaft position sensor signal, compare with known good pattern Watch
- Check pattern of bank 2 exhaust camshaft position sensor signal, compare with known good pattern Watch
- If your waveform analysis shows your cam/crank timing is off, mechanical engine timing will need to be checked and repaired.
Tip : Other components can cause the cam/crank timing to be off electronically, make sure to check for: Timing Chain Problems - A shifted reluctor wheeland for: Valve Timing (VVT) Issues if your waveform shows a cam/crank correlation problem