Hi All,

I have a 1998 Dodge Grand Caravan that will not pass inspection (for the first time ever in the 10 years I have owned the car). All emissions sensors now report not ready. The repair shop I took it to tried to get the sensors to ready by driving it through several drive cycles with no luck. They said I should continue driving it and gave me a recipe for a drive cycle that they swear by. I tried that for several weeks with no change.

Next, I replaced the battery and purchased my own OBD Scanner and have started over. Over the last several months I have run the car through many, many different drive cycle protocols and have put several thousand miles on the car since the new battery went in, and there is still no change in the ready status of any of the 5 emission sensors.

The only other symptom I can report is that about 6 months ago I had the transmission rebuilt, and the tranny shop said that they could not get proper communication between the PCM and the TCM and thought that the car had developed some electrical or computer issue. I did only the most rudimentary tests to confirm that wires which I think are the CCD bus lines between the PCM and TCM are intact, and not shorted to ground. The car seems to shift pretty well, so I did not pursue this, but now with the inspection failing, it begins to look more and more like maybe the PCM has failed.

1. Apart from taking the car to a Dodge dealer and start shelling out $, is there anything further I should do?

2. Since it's all and not just one or two sensors, I assume that if there is a defective component, it will be the PCM. Fair assumption? If I am told that the PCM is, indeed, on the fritz and I decide to try a junk yard, how specific does the PCM have to be for the car? If I get one for the right year and engine, is that sufficient?

And after installing it, is there anything else in the way of programming that a dealer would have to do to "introduce" the replacement PCM to its new home? Or can I expect the replacement PCM to light right up and function properly (assuming again that the old one was defective and the replacement a good unit)?

A lot to ask coming from a first-time poster, I know, but any help I can get would be most appreciated.

Thanks,
Peter Smick

 

Welcome to DF
To run all the monitors,I drive a least 40 miles. But I would also check the wires on the rear motor mount. Those wires go to the LDP pump.

 

Just for grins, though it takes some time, take a look at the solder joints securing the connector on the instrument cluster circuit board. It is by far the most common failure point in a CCD data bus issue. If you decide to I can link a video that explains how you get at it and make the repair. It often only takes a soldering iron and a bit of solder to fix it. I have to admit I've never read of this causing sensors not to show ready. Usually you'll see dead instruments, no cranks, shifting problems, etc. Could be the case that people with the usual bigger problems associated with the cluster connection just didn't have it happen close to an emmisions test.

FYI - one website of an ecm repair center states 70% of the ecms they receive for repair test good. That's certainly not to say your problem couldn't be the PCM but it's just food for thought. As far as required reprogramming for a junkyard PCM, I used to say get it reprogrammed period. Trouble is I've also read where for many it turns out to be just a plug and play move. So I can't say for certain if it will need reprogramming. It is best to get a PCM from the same model year and a matched security system meaning, if yours has the OEM security system, pick a van with the same system.

 

How funny! Two summers ago, my instruments began going intermittently dead and I was very proud of myself for pulling the cluster and finding exactly what you describe--a broken ground connection. I fixed that and the instruments have been fine since. I can't remember if I touched up just the broken connection or did them all. I guess I can have another look. Thanks for the tip and I'll let you know if I find something fun to report.

Peter.