Hey everyone, I'm new to the forum. Hopefully everyone can lend your expert advice. I'm helping a coworker out. She's got a 1996 Town & Country with the 3.8. She was driving it and it died instantly. They pushed it home (luckily she was just around the corner). When I initially got over there, her brother had been looking at it and said that there was no spark and that he suspected the coils.

I looked at it and I could get a fairly weak spark on cylinder 4, but nothing on 2/6. Later that day, I tried and got nothing on 2/4/6. When I say nothing, I mean I held an allen wrench in the spark plug wire with my bare hands and cranked the engine. There was NO electricity. He replaced the coils and it still didn't work.

I thought it might have been a timing chain issue, but if you look in the valve covers, the valves are moving. Obviously, this tells me the chain is still connected to the cam, but it doesn't really eliminate the possibility of a slipped tooth. (BTW, the car has 165k miles)

After some research on the internet, I came to the decision that we could look into the camshaft/crankshaft sensors. The prevailing opinion I saw was that the crankshaft sensor would kill the car if it died, but that with a faulty camshaft sensor, the engine would still run, just poorly.

I first replaced the crankshaft sensor, with no luck. We put the original back in there. This time, I had my code scanner and I plugged it up. It read a "camshaft circuit error." I was stoked. I knew that we'd tracked it down and all we had to do was replace the camshaft sensor. I purchased a new one and installed it. Still no luck. So now I'm throwing it to the experts.

Quick summary of steps so far:

Fuel pump works (plenty of fuel flowing when the schrader valve is depressed.

Sprayed starting fluid into the intake to check for fuel related no-start issues. Engine had no change in symptoms.

New coil.

New camshaft sensor.

Old crankshaft sensor. (but tried a new one w/ no change in symptoms)

Swapped out the auto-shutdown relay (term may not be correct, but it's the relay that shuts the engine down if there is a problem) Additionally, all fuses appear good.

Does anyone have any ideas what could be causing this problem? All symptoms indicate a no-spark condition, but I can't figure out why.

Thanks in advance for any help I may receive.

Mark

 

get a volt ohm meter at the coil connector u want one wire with 12v and the other 3 will have ground pulses see if u are missing any of that.

 

ChryslerTech,

I'll try that, but are we checking the Coil or something else? The coils have been replaced. What could cause any of the ground pulses to not be there?

Mark

 

just check it first u are worried about step 5 work on step one first

no u are not checking the coils u are check the voltage and grounds to the coil.

 

how about did you check ALL the fuses????

 

Here's the latest update:

Using ChryslerTech's advice and the procedure listed in Alldata's website, I troubleshot the signals going to the coil. This is what I found.

On the 12v wire, it was great. On the signal wires, one was constantly grounded and the other two were constanty high. These signal wires are supposed to be momentarily grounded to fire the coils and they come directly from the PCM.

I was unsure of whether the issue was my engine shutdown relay or possibly the camshaft/crankshaft sensors. I troubleshot it as follows: When the camshaft and crankshaft sensors are connected, the shutdown relay engages (as evidenced by a test light on the 12v signal to the coils.) If I disconnect either of these two sensors, the shutdown relay will not engage. This told me that the signals coming from the relays are working and that the PCM recognizes them. (because the PCM engages that relay).

Having said all of that, I'm not getting spark to my coils and, as much as I initially resisted this notion, I'm leaning toward a faulty PCM module. I do know that they die occasionally, it's just never happened to me (or anyone that I know).

I talked to a Service Advisor at the dealership and they didn't tell me anything that sounded cheap. They told me it would be $93 to diagnose, $93 to flash and $357 for the PCM module. (And that doesn't involve me getting the van towed to the dealership).

I've looked online and have sourced two different PCM's that would come pre-flashed (by the VIN) and ready to just plug and play. One is $150 and the other is $199. Both prices are certainly more attractive than the dealer quoted, but I'm wondering, does anyone believe that the problem is actually the PCM? Could anything else be causing the no spark signal to the coils?

Thanks for your advice.

Mark

 

where ya from? find someone with a scanner to check it. if you live around northeren IL let me know. I have a scanner. we will check it out

 

the wire that had 12v is from the asd relay
what wire colors were ground all the time? what is contently high? high what?

 

ChryslerTech,

Sorry for the confusion. I'm an electronics technician and I think I may not have been clear on what I was talking about. Because the wires that aren't the 12v wires (red/yellow tracer, dark blue/tan tracer, and grey in this case) are "ground when enabled" wires, when they are not "active", I would call them high.

Just to be clear on my testing method. When testing for the 12 volts, I used a test light. The clamp goes on the battery ground and the probe went into the dark green/orange wire. When cranking the engine, the ASD relay energizes and the 12volts is applied to the coil. (This portion worked perfectly)

The next step involved testing the remaining three wires on the coil connector. They are momentarily grounded to fire the respective coil. The ground signal comes directly from the PCM module. Because we are now dealing with a "ground when enabled" signal, I switched the clamp on the test light to the positive terminal of the battery and placed the test light into the other three wires on that connector (one at a time, of course). The dark blue/tan tracer wire lights the test light immediately and it remains on the entire time you are cranking the engine. The remaining two wires will never light the light. In a functioning engine, the light would flicker when the engine is cranking.

Because the light instantly lights and remains lit during cranking, it is a constantly grounded signal. Because the other two wires never turn the light on, they are remaining high.

I hope that clarifies what I've done.

Every step I've taken leads me back to thinking it's a faulty PCM module. I initially resisted this notion because it's certainly the least likely culprit. But I'm now convinced that the CKP/CMP sensors are working because if I disconnect either of them the ASD relay doesn't energize.

Prior to purchasing a $150 PCM, I was just looking for some consensus on that thought or some other possible causes.

Thanks again.

Mark

 

ok next step unplug the pcm connectors and check for that wire to have a ground again if there is still a ground then u have a wire that is shorted to ground from the coil to the pcm. if the ground is gone then yes bad pcm