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Thread: No RPM Signal

  1. #1
    Tuner in Training
    Join Date
    Jun 2019
    Posts
    14

    No RPM Signal

    Hi All, I need your help. (3.6 V6 from Pontiac G6 in an MGB E67 controller)
    Recent no start.
    - Put the VCM Scanner on and noticed that I had no rpm signal or crank or cam counts during crank. No codes are set, no cam errors detected and good cranking speed. Throttle works, spark and fuel settings seem to be correct, ECT and air intake temps are OK.
    - I suspected the crank sensor but both wiring verification (5V Ok, Ground OK and Signal wire to the correct pin at the ECM) and a replacement sensor made no difference.
    - I do get a "Medium Res Count" increment when I short the sensor wire to ground or wave a metal object in front of the sensor. Similarly I get cam counts if I short one of the sensor wires (4 cams) to ground.
    - According to the diagnostic procedures, the sensors and wiring should be good and since the counts increase manually, the ECM should be OK. In any event I tried changing the ECM to a stock Pontiac G6 with no difference.
    - I was then worried that there might be something wrong with the reluctor as there had been a service bulleting about the wheel having moved and giving the wrong input to TDC. The best I could do was to check it with my finger and it seems to be OK (not loose) and the depth to the wheel is about 1/8" longer than the sensor, which is about right. If the timing is off it might cause erratic running and codes set but shouldn't affect the sensor counts/rpm.
    - I also tried a different scan tool and it too does not read any rpm during crank.

    I would appreciate any ideas or thought that you might have (other VCM settings?)
    Thanks in advance

    [B]New Info!!
    While I still get no RPM or sensor pulses, the engine tries to start if I spray ether into the intake. How is this possible if the ECM is not receiving crank and cam sensor data? Is there possibly an issue with the VCM? Any Ideas?
    [B]

    Engine runs and having borrowed a different scanner, there is an RPM registered. The VCM is not recording Fuel Inj. pulse width, RPM, crank or cam counts, MAF. It does record IAT, ECT, MPH, and spark advance. It also does not detect any codes while the stand alone scanner detected codes re. cam sensors. Any idea why the VCM isn't working properly?
    Last edited by HFV6MGB; 08-10-2024 at 03:08 PM. Reason: New Information