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About three months ago my 96 Dodge intrepid died while driving and had to get towed hone. The check engine light had come on right as the car died. After a KOEO an audible chattering was coming from the fuse box, and upon inspection it was the auto shutdown relay stitching on and off – a short somewhere in the PCM’s 5v reference circuit. I was observing that while the rail was pressurized properly, the injectors were not firing. To narrow down the problem, I began removing connections to the MAP, TPS, et. al with no change in the relay stitching on and odd. I removed the cam sensor connector and viola, the relay stopped. I verified that I had my 5v reference signal at the connector as well as good ground and that my 8v outout was good as well and they all read normally, so I knew the sensor was bad. I replaced it, the car ran again with no issue.
A few days later I went to start the car and it cranked but would not start. I popped the hood, and observed three wires bare right at where they go into the actual plastic connecting piece on the connector harness for the cam sensor. Figuring that this was likely what caused the initial sensor to fail and was most likely touching the intake manifold and grounding out or even the three wires touching themselves together and creating an intermittent crank no start due to loss of signal from the cam sensor, which this engine requires to at least start. Upon “wiggling the wires” in the right position, the car started fine. So I initially used electrical tape to cover up the exposed wiring and then taped the connector harness to limit it’s movement. This effectively resolved the issue, only once a week or so flaring up, but easily and nearly instantly resolved by simply adjusting the wire position.
Over time, the tape wore from heat and the vibration of the road and the issue went from happening once a week to daily, with increasing difficulty in getting it to start. Today, it became almost every time the car was turned off, the engine would not restart. So I carefully removed all the tape and disconnected the harness to test it with a multimeter.
My initial test read the proper signal and outout, but when I measured continuity on the ground, instead of the 0.05 I got from verifying good ground at the alternator, resistance read 0.9. 9ohms? No wonder this PCM can’t detect a cam signal, there’s too much resistance in the sensor’s ground wire. The car would not start with this reading.
I conducted a second test and was able to finally get the DVOM to read the proper 0.05ohms at the ground, and the car started immediately. What this tells me is I have intermittent resistance in the ground wire of the cam sensor, causing the PCM to be unable to process the proper signal from the sensor during startup – and no cam signal means no fuel deliveryv on many of these Chrysler engines.
My question is this – I don’t have the necessary tools to trace this ground wire back with a miliamp or scope and find where this short or resistance is. Even if I did, I would have to remove the intake manifold and fuel rail to get to this harness. So, exactly where does the ground for the cam sensor go (where does it ground out at) and would it be possible to solder in a new wire at the connector itself and ground it directly to the body of the car or another suitable ground in the engine? Do I have to repair the wire because for some reason it requires grounding out at the PCM, or can the PCM in this case be bypassed as far as the ground goes?
Essentially, is this a practical temporary fix until I can repair the harness itself? Or would the actual ground wire going to the PCM need to be repaired.
Thanks a ton guys for any help.
Just wanted to give a quick update – the troubles continue into today, but I have been able to gather some more data.
Here are the DTCs for my 1996 Dodge Intrepid 3.3L V6 176,xxx
PO340 – Camshaft Position Sensor Circuit Malfunction
PO1596 – Speed Control Switch Always HighThe car will start when the resistance on the ground wire to the camshaft sensor is at the proper 0.05ohm reading. So I can tell my car will start as soon as I can get this reading. However, what was once an occasional intermittent issue has developed into every time the car is turned off, it will not restart.
I can’t seem to find any pattern to this behavior. Having an assistant hold my DVOM in place, no amount of adjustment to the wire or the connector itself will drop the resistance. So in an attempt to create a manageable and observable change in this behavior, I started at the very beginning of the entire circuit. With DVOM in place, I adjusted the positioning of the
hot batteryy terminals and observed an immediate DVOM response – reading changed from 0.39 to 0.31. Intrigued by this, I removed the hot terminal entirely and the DVOM stabilized at the wire at 0.05ohms and stayed there. I’m not entirely sure what to make of this new information yet, but from what I’ve gathered, the speed switch code could either be an additional result of a bad chasis or engine ground or the cause of the problem if that circuit is running too high and bleeding over into the PCM circuit. It’s amazing to me I can get this car to start and stay running at all, considering that according to my wiring diagram, the entire PCM circuit uses the same blk/lt blu ground wire.To me, it seems most likely that there are crossed wires or circuit bleedover somewhere – specifically, a hot wire and that black ground PCM wire touching intermittently or something. Anyone have any ideas? I really need help with this diagnosis.
(Also, I was able to note somewhat of a correlation from temperature and resistance. Seems as temp goes down, so does resistance. A friend noted light corrosion on the hot battery wire. I’m trying to figure out how to isolate the part of the circuit causing this resistance but I was able to verify by pulling a few other sensors that the resistance is shared through the circuit.
Hey guys, more follow up here. Did a key dance to get MILs and this was my result:
12 22 23 34 42 51 54 55
12 is battery disconnected within last 50 key cycles
22 is engine coolant temp input above or below expected levels (ECT shares the same ground as camshaft and on my engine, literately splits off in the harness right at these two sensors, I see normal operation so I don”‘t suspect this as an issue, most likely bleedover from can circuit errors).
23 IAT above/below expected levels (once again, this sensor is the next in the circuit from the camshaft and is on the same wiring harness that runs underneath the fuel rail – I’m suspecting ny issue lies in this harness.
34 open or shorted condition in the speed control circuit (the PO1596) probably will just pull the cruise control fuse because I don’t use it and this DTC is very annoying and counterproductive to diagnosis
42 open or shorted condition in the auto shutdown relay (from the cam sensor shorting)
51 Lean fuel/air ratio detected by excessive rich correction (this one probably set when I had a minor hydrolocking incident recently (obviously when water is introduced to the intake the engine displays a lean condition and rich response before halts to a stop. Lucky for me, it almost immediately restarted with no sign of internal damage. Just ran shoddy till she got the water out of the exhaust)
54 no cam signal detected during crank
55 End of MIL sequenceSpeaking of the hydrolocking incident, ironically since that happened I cannot get that ground wire to display any resistance whatsoever now and so the engine has started every time. I have a new CEL though now, and haven’t been able to pull the DTC yet, but it went off and stayed off, but displayed on restart so it had to have been set today so maybe when I can actually pull that with a scantool we’ll get an idea of what is happening now.
Eric O. of South Main Auto has fixed several bad grounds on Mopars. It seems to be a common problem. Since you have multiple concurrent failures it is more likely to be something they have in common. If you can get ahold of a wiring diagram you might be able to trace the ground wires to see if they are all attached together. Keep us apprised of the situation.
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