P0353 Misfire Nightmare – Throwing in the Towel - '96 T&C
 

About 15 minutes after replacing the PCM for a no-start problem, our 1996 Town & Country 3.8 suddenly started misfiring and generated a code P0353. It’s a fault related to the #3 coil circuit. There were no warning symptoms. One moment it's fine, the next it isn't.

This van had always run great. I was sure this problem was a bad rebuilt PCM so after testing the #3 coil circuit and wiring for continuity per Chrysler specs, I had another PCM sent out. The second PCM was installed and the engine has the same misfire and throws the same code.

Thinking I had tested something incorrectly, I installed a new coil. Same problem. I even cut and jumpered the #3 circuit control wire directly from the PCM to the coil. Same problem. Used a light tester to see if the #3 circuit control wire was actually getting the ground signal from the PCM to the coil. It is.

A mechanic on another site was diagnosing a similar problem for a customer and insisted the customer change spark plugs because he was running platinums. Our van had Bosch Dual Platinum plugs for about 70k miles and ran stellar. Great plugs. This time I went cheap and installed Autolite Platinums. I really don’t see how these plugs could be part of the problem, but I pulled the two plugs associated with circuit #3 and swapped them with two others that are working fine. Same problem. I installed new plug wires as a last ditch effort. It was a waste of $30 and a whole lot of time.

Everything in that circuit, literally, from the PCM to the spark plugs, has been replaced or swapped with good working parts. I am absolutely baffled and ready to scrap the thing.

When you hardwired the control circuit wire, did you take the existing wire out of the mix or did you go parallel? If there is a voltage bleedover in the wiring harness then hardwiring and leaving the existing wire connected will throw you off.

I cut the RD/Y wire at the PCM connector and at the coil connector and used a new section of 16-gauge wire. After the test I soldered the ends of the stock wire back together and used heat shrink at the solder joints.

Later I used a light tester at the coil connector and got a good, bright flash so the existing wire is fine. My bypass control wire test was more desperation than anything. Kind of like the plug wires.

Unless someone has put a hex on the van, there has to be a logical explanation for what's going on. It would be helpful to know exactly what signal the PCM is getting from where to generate the P0353 code. The only source I can see is the #3 circuit control wire itself. There is no other monitoring for the ignition system or spark plugs that I am aware of.

The coil ignition and control system is really simple and since I now have extra plug wires, I'm thinking of getting a couple of Bosch dual platinum plugs because I know they work well with this engine, connect them to two extra wires and the circuit #3 coil outputs, ground the plugs and see if they spark. If not then maybe a try at a new coil again.

This isn't rocket science. B+ feeds all three coil circuits via a single wire. Each pair of circuit coils is then briefly grounded at the appropriate intervals to create spark. It can't be this difficult. I must be missing something obvious.

Problem solved...sort of
 

I always find it irritating when the initiator of a thread finds a solution then just goes on their merry way and never bothers to follow up with what they found. So with that in mind, here's how I fixed the problem with my van-

I sold it.

Movin' on...