'97 intrepid in limp mode: code 0731

QuestionEdit

QUESTION: Our 97 Intrepid 3.3 is in limp mode. We have a second car for parts to repair. Behind the battery there is an electronic device (I don't know the name) that was loose and when removed and reconnected the car ran correctly for about 24 hours, so we suspect an electrical problem. Since then we have replaced the EATX relay with no effect.

We have seen advice to test or replace the solenoid pack and the transmission control module. I do not know where either of these are located or how to change them. Is this advice going in the right direction and can I find a diagram of the transmission and components online? What other steps would you suggest?

ANSWER: Hi Chris, There are two electronic pack between the battery and the power distribution center box, the forward one being the transmission controller, the rear one the engine controller. I would recommend that you get a diagnotic readout of the transmission control module memory using a plug-in code reader that goes into a socket under the dash. Find out the 4-digit numbers that are store in both the engine and the transmission controller memories, ask what the numbers mean, and what the repair might be. Then get back to me with a follow-up question and we'll compare notes. There is no point in throwing parts at the 'limp mode' until you have the fault code numbers. You can often get a free code readout at a nationwide auto parts store, such as Autozone or for $40 at an independent shop. Please 'rate' my answer (see below). Thanks, Roland

---------- FOLLOW-UP ----------

QUESTION: HI Roland, We have the codes -p0731, p0432, p0700 - I understand that 731 refers to gear ratio and speed sensors, so we changed the sensors, since we have the spare car here. It did not help, so it would seem we are down to a wiring problem? Any other ideas?

Thanks, Chris

ANSWER: Hi Chris, The 0432 means that the catalytic converter efficiency on the right cylinder bank has degraded and needs replacement, unless you have evidence of an exhaust manifold to cat. converter leak in which case try repairing tne leak condition. The 0700 confirms the presence of a specific trans code, the 0731. That one, while it says there is a speed ratio error doesn't specifically implicate the speed sensors as the problem but also of course the wiring of them, and then a great many other possible causes. About the only two that don't involve removal of the trans, other than the wiring, are malfunctions in the solenoid pack or the pressure switch assembly which are removed by dropping the pan of the trans and removing those parts for inspection and servicing as found. So doing that might be worth it compared to remove/rebuild. But if you have high mileage on the unit then you might give up on those and go for the rebuild. There are numeous reasons for slippage of the internal parts, too numerous to list unless you intend to do the rebuild yourself. The wiring check from the sensor plug to the TCM is simple: the common ground wire on pin 1 of the plugs goes to pin 13 of the TCM plug, while the signal from the input sensor on its pin 2 goes to pin 52 of the TCM plug, and the outpur sensor signal goes to pin 14 at the TCM. So check those wires for continuity. Please "rate" my answer. I appreciate your earlier rating/nomination and in fact you are permitted to do that again with each new question you submit. Thanks,

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QUESTION: HI Roland, Thanks for the help. We have continuity on 13 and 14, but not on 52. It seems unlikely that the wire itself is broken since they are well protected so I am assuming that the most likely place is the actual connections. Can the harness to the TCM be changed? It looks like it is two pieces, but I did not want to force it apart if it was not supposed to separate. I have not checked for continuity on the wire separate from the connectors, but I can do that.

Any other ideas on how I should proceed?

Thanks, Chris

AnswerEdit

Hi Chris, I would suggest that you use fine pins to probe through the insulation on the red/black wire near the plugs, to see if the wire is open or the disconnect is between the wire probe pins and the nearby plug pin. Depending upon what you find there may be a 'fix' that doesn't involve replacing the entire harness which may be either complex or costly (unless you can get one at a wrecking yard). I don't know the details of replacing the harness so let's determine where the 'open' is located. In one respect, if the discontinuity is the issue, that is much better than there being an actual problem inside the transmission! If you would care to 'rate/nominate' again feel free to do so as you can do so with each answer I provide.

Roland