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How to Test a GM 3.6L Timing Chain

  1. 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
  2. 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
  3. 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

  1. Adjust your labscope software to get a useable pattern, recommended settings (0-10V scale, 20m/dv time base). Watch
  2. Label channels with their corresponding sensors to aid in waveform analysis Watch
  3. 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
  4. Check pattern of bank 1 intake camshaft position sensor signal, compare with known good pattern Watch
bank 1 intake waveform
  1. Check pattern of bank 1 exhaust camshaft position sensor signal, compare with known good pattern Watch
bank 1 exhaust waveform
  1. Locate the two bank 2 camshaft position sensors. Back probe the middle wire of each sensor connector to acquire a signal Watch
  2. Acquire waveform using same voltage and time scale and zoom in on one full engine cycle or two crankshaft revolutions. Watch
  3. Check pattern of bank 2 intake camshaft position sensor signal, compare with known good pattern Watch
bank 1 intake waveform
  1. Check pattern of bank 2 exhaust camshaft position sensor signal, compare with known good pattern Watch
bank 2 exhaust waveform
  1. 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 wheel and for: Valve Timing (VVT) Issues if your waveform shows a cam/crank correlation problem