QuestionNo spark on this vehicle.
I found Roland's instruction to user "Rose" regarding testing system at the coil plug:
QUOTE:
"Then we have to determine whether you are getting 12V to the coil pack when you are cranking it and also whether the 3 'drivers' for the 3 spark coils are working. If you remove the plug-in for the coil pack you will see four contacts. If you hold the plug so the locking tab is down (and the indentation is thus to the left) then the 12V primary supply voltage for the coils will be present on the upper right contact. While cranking the engine see if in fact you get a steady 12V on that contact, using a voltmeter or neon glow lamp with one lead on ground (any metal surface of the engine) and the other lead on the upper right contact. If that is present then it proves that the crank sensors, ASD and computer are o.k. as far as power to run the coil pack is concerned.
Then use the voltmeter or glow lamp to test if the other three contacts of the coil pack plug are each being momentarily grounded when you crank the engine, in synchrony with the speed of rotation (each should be grounded once for every two revolutions of the engine, so if the starter is cranking at 350 rpm the glow light should pulse about 3 times per second). Put one wire of the glow lamp on the + post of the battery for a voltage source and the other wire should be used to test each of the other three contacts of the plug: the upper and lower left and the lower right contact..."
END QUOTE.
After having replaced both the crank and cam sensors, I was advised by a tech the only thing left was the ECM. I wanted to try one last test to verify; found Roland's instruction and followed it.
I find 12v at the upper right pin of the coil plug, (while cranking, nothing at rest) coil drivers for 1/4, 2/5 pulsing as per Roland's instruction. Driver for coil 3/6 (18 ga RD/YL wire) gives me a steady light. I followed wire harness from coil plug as it travels under the intake, through a plug, then through a larger harness- found no breaches, or shorts.
Am I safe enough to assume the ECM is indeed bad and spend the $292.++ dollars to replace it? One thing I did note while working on this issue; if I crank down to the end of the battery charge, right before the starter drags down to a stop, the system will attempt to fire. By then voltage is too low to sustain proper operation of the system, so no start.
Thanks in advance for your assistance!
-=Larry=-
AnswerThis question gives me the feeling of jumping onto a raft as it's rushing downstream. So I'll do my best to keep my feet, so to speak. I would not condemn the PCM yet. Unless I missed something or there is more of a back story, these are my thoughts on your problem. You've verified that the PCM is sending a signal to the coil pack to fire off at least two of the coils. You've also verified that there is no spark output from the coils, which I hope you checked at all plug wire locations. It would seem logical at this point to suspect that the coil pack itself has failed. I would also check one other thing. Under the battery tray there is a ground lug/screw that is prone to loosen up and corrode. This ground is critical for the PCM. Check it for any looseness or corroded/broken wires.
