QuestionQUESTION: Hi, should pins 1 and 3 on the coil plug both pulsate ground when cranking with the key on? I have 12v flat on pin 2 - pulsating on pin 1 and 12v flat on pin 3- no pulsating.New cam & crank sensors - new coil - 8v on cam-crank sensors and pulsating voltage 5 - 0.3.
Thanks, Bronac
ANSWER: Hi Bronac,
Pin 3 should pulsate identically to pin 1, except alternatively in time (but you wouldn't be able to observe without a scope). Check to see if the wire from pin 3 of the coil plug to pin 2 of the pcm is connected. If it is, then I wonder if the cam sensor target magnet itself might be damaged, so you might consider replacing that. The output of the cam sensor should change voltage 4 times for every 2 revolutions of the crankshaft, approximately evenly spaced but not exaxtly. As it stands now, only 2 of the 4 spark plugs should be sparking (cylinders 2 and 4).
Roland
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QUESTION: Thanks Roland,here's the update.I think I have a ground issue in the ECM.Pin 3 has no pulse and ground all the time even with the key off.If I unplug the ECM the ground goes away.The target magnet looks OK.I also unplugged all the injectors-crank & cam sensors - TPS -MAP- and idle air sensors and the ground remained.Do you agree the ECM is bad or have more suggestions? Thanks again, Bronac
ANSWER: Hi Bronac,
I assume that you are testing right at pin 3 of the ecm, but you have checked the wire from pin 3 to the coil pack with the ecm plug removed to be sure that wire isn't grounded, correct?
I have not had experience with how the ecm might exhibit a failure except if it put out a code for that.
But if the wire is not shorted, then it would be plausible to think it is the ecm. But I know this is not an inexpensive part so don't want to 'guarantee' that replacing it will solve the problem.
Roland
PS Please 'rate' my answer, and where you see the question about 'volunteer of the month' please consider a 'yes' response. Thank you.
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QUESTION: Hi again Roland, the wire from the coil to the ECM is not shorted.No ECM codes. Anything else? At the plug to the coil I have pulse on one side and flat ground on the other- no pulse. Does this help? It tries to start but won"t.Thanks again, Bronac
AnswerYou might want to be sure that you are indeed getting the pulsing on the cam sensor as I described because if half the pulses were missing that would explain why you are only getting pulsing on one coil driver wire. If you are getting the pulsing on the cam sensor then it has to be the ecm. The magnet might be bad but not show it, except for the pulse rate being halved.
Roland
