QuestionQUESTION: 1995 Dodge Grand Caravan ES. 240k on it, owned since new and I do most of my own work. The instrument cluster started going out on me recently (speedo, tach, gauges all went flat) after a while it would come back on. Everything else worked ok and the car would drive fine. Pulled the cluster out of the dash re-soldered some connections on the circuit board, checked out connections in the dash etc. put it back in, still had the intermittent problem.
Then what started to happen was that the tranny (new tranny @ 170K, well maintained) would go into "limp mode" when the cluster would go out. Sometimes if I went under the hood with the engine off and jiggled a few of the the wiring harnesses, everything would be fine for a while. I tried cleaning the contacts to the PCM and TCM, that didn't do it. Replaced the input and output speed sensors, no change. Figure its a bad wire someplace but I can't find it. Could it possibly be a bad PCM or BCM? Also, I can't find a DRB scan tool, do you think the dealer will read the TCM codes for a fee even if I may not have them do the repair? Any ideas would be greatly appreciated.
Thanks in Advance,
Brent053
ANSWER: Hi Brent,
Based on the cluster going 'out' when the trans goes into 'limp' I believe that this is related to a problem with the CCD+ and CCD- communication system. It knits together the pcm, tcm, bcm, overhead console, cluster, data link connector (under the dash) and data link connector in the engine compartment via a pair of twisted wires (violet/brown) and (white/black). There are also two splices under the dash buried in a thick harness near the cowl panel on the left side.
The problem could be with one of the two wires being shorted to ground or to 12V, or just an open connection at a crucial spot, or the failure of one of those many components that are part of the bus.
My thought would be to indeed try to get a readout via the rectangular black 8-pin socket under the dash on the driver side using either a DRB II or an exquivalent Snap-on tool of that vintage that have the appropriate software to see and display what it sees as wrong. You don't have to go to a dealer but you might find an autoelectric shop with a Snap-on that will do the reading. Either a dealer or such a shop will do the readout for a fee without making a committment to do the repair. I am in the SF Bay area in California if you happen to be near and have a DRB II. Other than that, inspecting all those devices' plugs and shaking the harnesses is the only thing I can suggest.
Roland
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QUESTION: Roland:
I think I found the short and got the instrument cluster working again however, the tranny is still in limp mode. Is there someway to clear the PCM/TCM codes without the DRB scan tool. I've heard of a couple ways to do it but I'm not sure if their safe or not. One is to unhook the neg battery terminal and then turn the ignition key to on for 15-20 minutes. Then hook up the neg. terminal again. The other is to unhook both neg and pos terminals and hold them together for 30 seconds. Your thoughts are certainly appreciated. Thanks.
Brent053
ANSWER: Hi Brent,
Usually codes are cleared simply by disconnecting the - post cable clamp from the battery and then reconnecting it. No risk of doing that. A 'soft reset' involves doing that clamp removal and as well after taking off the - clamp touch it together with the + clamp for a half a minute, then reconnect the - clamp to the battery. That not only cancels the codes but also discharges any capacitors in the electronics that are connected to the battery. If that doesn't get you out of limp mode, then a readout of the tcm memory with a reader plugged in under the dash is the next step. Let me know what codes you get and we'll go from there. I believe the reader has to be a DRB II or similar level Snap-on to access and retrieve the TCM codes which still in '95 were 2-digit numbers, just like for the PCM so they overlap and you have to have a reader that can communicate which memory it wants to communicate with.
Roland
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QUESTION: Hi Roland:
Per your suggestion, I had the codes pulled and they came up with code 43 which they said indicates a problem with the OD Solonoid Circuit. They said it could be a bad connection between the TCM and the Solonoid Pack. I'm hoping that is the case and that I don't have a transmission that is shot. Still in Limp mode though. What do yopu recommend?
Thanks,
Brent053
AnswerHi Brent,
It could simply be an problem in the solenoid pack which generally is replaced as a whole unless you want to try and repair it. The wiring should be check first:
The OD solenoid connection is pin 60 of the tcm to pin 6 at the solenoid pack. The OD pressure switch circuit is pin 9 of the tcm to pin 3 at the solenoid pack. If those are continuous and not shorted to ground when you have both plugs removed from their sockets then presumably there is a problem with the solenoid proper and so you would try replacing the solenoid pack. You can do that yourself because it is on the outside of the transmission. You simply remove the input speed sensor, then the sound cover, and finally the three screws (vertical) that hold the pack in place. Watch to be sure the gaskets are all back in place.
Roland
