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Chrysler Repair/'98 minivan: limp-in mode when speedo quits

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QUESTION: in my 1998 voyager the speedo started to work intermittently and it wont shift out of second gear when the speedo quits working. i changed the speed sensor and that hasnt fixed the problem. checked the TCM and it seems to be working properly, do you have any other suggestions? also just so you know, when the speedo decides to work, it shifts through all gears perfectly.

ANSWER: Hi Richard,
I would focus first on the output speed sensor and its circuit. Was that the speed sensor that you changed out? If not, then do so. You should check its wiring; the dark blue/black wire should be connected to pin 13 of the transmission control module, while the red/black wire (on pin 2 of its plug) should be connected to pin 52 of the tcm. Shake the harness gently while checking the continuity of those wires.
The other thing to do is a fault code readout using a plug-in code reader. A nationwide auto parts store, such as Autozone, will often do that for free. Or an independent shop will do it for around $40. Get the specific fault codes numbers, ask what they mean, and what t advise. Then write back and we'll compare notes with the shop manual.
Please 'rate/nominate' this answer/me (see the PS below).
Thanks,
Roland

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

QUESTION: Thank you for your prompt response. We have already tried to have the code read and it says it can't read it.. And on the in dash all the drive features are light up(D,R,P, ECT) we know the TCM is good bc we tested it in another vehicle, but the code reader isn't able to communicate with the transmission so is this possibly a PCM issue? Thank you again for your time.

Answer
Hi Richard,
The gear lights all being 'on' does mean that there is an issue with the digital data about which gear is in use from the TCM not getting to the PCM at least, and there could be an overall issue with the digital data bus that connects the TCM, PCM, BCM, and several other components because the code readout balks. It may be to your advantage to try a more sophisticated code reader which might give you some specific answer as to exactly what is sees is wrong with the data bus. You could then either unplug the various modules one at a time and see if that changes things or you could measure the voltages on the data bus wires to focus in on which wire is 'bad'.  
There are a couple of trouble-shoot procedures that I can copy from an '04 manual I have on a CD and attach them to an email which I would send to you directly. To do that I need to know your email address, but don't us the @ symbol, instead use "at", otherwise the address will be automatically erased. Also mention which (L) engine you. Also, I can photo copy and postal mail you a couple of pages from the '98  hard copy manuals about the data bus system and its trouble- shoot. I would need your postal mailing address to do that.

Some other things to check: fuse 15 in the power box in the engine compartment might have an intermittent output due to a subtle crack in its wire so look closely at that. Similarly check fuses 2 and 10 in the cabin fuse box. Check the continuity of the wire that connects from the TCM to the PCM and carries the speed sensor signal: white/orange from pin 58 of the TCM to pin 66 of the PCM. Also check the continuity for the data bus wires from the TCM to code reader socket: pin 4 and 43 of the TCM to pins 11 and 3 at the code reader, respectively. Also check from pin 7 of the TCM to pin 65 of the PCM (pink wire). Gently shake the harness while checking for continuity.

Thanks for the rating/nomination, both of which you can do again if you feel so inclined.
Thanks,
Roland  

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Roland Finston

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Get a Free Fast answer to your repair question about a Chrysler/Dodge/Plymouth car, minivan, SUV, or truck. Problems with electronically controlled engines and transmissions as well as body wiring problems are my specialty. This free troubleshoot advice forum helps you diagnose faults, minimize repair costs or do-it-yourself.

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I have do-it-yourself experience (50+ years) and a library of 100 1982-2012 Chrysler factory shop manuals and 20 multi-manual Chrysler Corp. CD's.

I was voted "Top Expert" 2010-2015, here at AllExperts, and have answered 20,000+ questions.

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Five decades as a 'do-it-yourselfer' on domestic and imported cars.

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Yahoo Autos Group called The Chrysler Lebaron Club (co-moderator)

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Advanced degrees in Physics/bruised knuckles

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"Top expert" of 2010, 2011, 2012, 2013, 2014 and 2015 here at Allexperts. Quickest "average response time" at Allexperts (currently no. 1).

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