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Communities > Diagnostics > USA Cars > no cranking signal for ign/fuel
no cranking signal for ign/fuel

3053 Views 7 Replies Latest reply: 2017-04-23 22:01:43


  •   Level 3   
    (55) points
    bestresultscarcare
    2015-11-10 09:29:29

     I'm throwing this out there, as I have been stumped. 97 Jeep wrangler 2.5. Car quit while driving. Had code for crank sensor. Found crank sensor wire against exhaust manifold, one wire grounded (5v supply). Replaced sensor, still no ign/fuel activation while spinning over (it does initially power up when key is turned on) re-tested crank signal, initially ok (received 5v on/off on signal wire / next time testing (done repeatedly) found 5v continuous on the signal wire (gray/blk) . I now have 5v being sent out from ecm on the signal input wire. Same on cam signal input wire. It is not the ecm. I cannot find problem. Any ideas?????

    thanx, Kirk


  •   Level 9   
    (5837) points
    Ashraf

    2015-11-10 12:15:13 (Reply to:bestresultscarcare)

     Have you checked all the fuses..............? It could be when the sensor wire was shorting to the exhaust it could be it has blown some fuses..............well I know the sensor wire is coming from the ECU but, worth checking the fuses..........................

  •   Level 2   
    (47) points
    autotech

    2015-11-10 21:17:15 (Reply to:Ashraf)

    The cam and crak sensor share a common pcm ground c150 check at pcm look for
    ground that feeds both sensors check at connactor for the ground if not work your
    way back to pcm also check pcm powers and grounds. Good luck

  •   Level 6   
    (489) points
    tech54

    2015-11-12 20:55:14 (Reply to:bestresultscarcare)

                  Aleady got good feedback from Ashraf on the voltage supply that the hall-effect needs to maintain a magnetic field and Auto-tech talked about the ground needed also to maintain that magnetic field for switching. I'm following your description unplugged on the CMP and CKP signal wires the PCM is supplying 5 volts so the hall-effect does a pull down of that signal line so if at 5 volts all the time you won't have ignition or injection that's your problem. I doubt mechanically you could have an issue with both the distributor and flywheel windows used by CMP and CKP. Recheck the orange wire for power cranking (load test) and also the ground cranking (load test). You didn't mention if CMP is working but you could try a by-pass test (quick tap repeated ground with test light) to check for spark and noid.Scanner graphing RPM with enough taps might verify PCM sees signal. Noid light and spark checker to verify PCM did it's job. Good luck

  •   Level 7   
    (1473) points
    Kevin H

    2017-04-18 01:36:16 (Reply to:tech54)

     I would unplug the crank sensor and make sure you have a ground there. If your signal wire is stuck high, that tells me that the sensor is not pulling the signal to ground. The sensor will not be able to pull the signal to ground if it has no ground supply to it. The ground being supplied by the PCM, it is possible that you have a broken ground between the sensor and the PCM.

  •   Level 7   
    (817) points
    spikeoo7

    2017-04-19 02:33:01 (Reply to:bestresultscarcare)

     try another crank sensor if not  OEM

  •   Level 7   
    (862) points
    SmogTech87

    2017-04-23 19:15:41

     Almost two years has been passed since he posted the problem. He never reply the outcome!.

  •   Level 7   
    (1473) points
    Kevin H

    2017-04-23 22:01:43 (Reply to:SmogTech87)

     Wow Smog! I never noticed the dat on his post. I thought it was recent. I have to start paying attention to that.
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