QuestionQUESTION: Okay guys I'm at wits end with this vehicle, 98 dodge startus 2.4 doch, here's the thing it won't start! Checked the connecter, wiring, changed out the cam sensor and no start but if I leave the cam sensor unplugged it'll start! Now it shouldn't start with out the signals right? Checked for continuity to PCM and I'm good. Everything is within spec. Would greatly appreciate any help I could get!
ANSWER: Hi Yue,
It could be that the cam sensor is shorted to a voltage source which messes up the synchronization of the injectors entirely and when it is unplugged there is a 'no signal' default to a condition where paired injectors are fired instead of individual which allows for the engine to run although not as good as it could (similar to the spark timing situation). The spark timing is set by the crank sensor only and because there are 2 coils for the 4 cylinders two spark plugs will always fire regardless of the cam reference signal being present or not.
I would plug in the cam sensor and test for voltage to pulse between the signal and signal ground wires by inserting pins through the insulation of those wires at the pcm plug. The sensor signal is on pin 33 and the ground is on pin 43 (tan/yellow and black/light blue, respectively). You would put the ignition switch in the 'run' position and then turn the crankshaft via the crank pulley bolt. The voltage signal should change from 5v to 0.3v once per revolution of the crankshaft. If you don't get pulsing then either the orange wire at the sensor doesn't have 8 volts on it (which comes from pin 44 of the pcm) or the sensor is not properly spaced relative to the spinning magnet on the camshaft, or the magnet is degraded.
Please let me know what you learn.
Roland
PS I have heard of this before so you are not unique.
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QUESTION: Sorry for the slow response I took a few days off. But I just checked it and yes we are getting a signal from 5v to .03v but I just noticed that the specs you have listed is 5v to .3v could this be the problem? I dont know where to go from here! Got a friend to bring by a PCM and installed that one but nothing still, even with the cam sensor unplugged it wont start with the second PCM. Any ideas??
ANSWER: That pulsing to 0.03V is ok for the 4 cyl cam sensor according the the Haynes manual. It would be good to verify it at the pcm plug of that signal wire just in case it is 'open'. I can't recall the situation with the crank sensor, have you checked its pulses? The the fact that it will start with the old pcm and not the replacement pcm (when the cam is unplugged suggest something is wrong with one or the other pcm, but I don't know which. But again, check that signal wire for continuity and try shaking the harness while you measure.
Roland
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QUESTION: Hey Roland figured this out last week, but hadn't had a chance to reply. First I would like to take this time to thank you and the site. Second of all the problem was timing, it jumped, don't know how or why everything seems okay that's involved with the timing belt( belt,tensioner, etc). It makes sense now why it wouldn't start with the cam sensor plugged in, man those stupid obd2 codes pointed me to the right direction but I was stupider for even not considering it. But thanks again and I don't know how to rate you but I'm sure if there's a way I'll figure it out eventually.
AnswerHi Yue,
By "timing, it jumped" I assume you mean the cam/crank timing marks were 'off'. Please let me know if otherwise. It is an interesting phenomenon that you discovered. I will try to keep it in mind if anyone else has this symptom.
If you would like the 'rate' me, notice the 'thank/rate' tab which should be below this answer. Thank you.
Roland
