92 Plymouth Voyager limp mode, help!!!

[lon]

I bought this 92 Plymouth Voyager couple month ago, but since I got it, it stuck in limp mode intermittently. No mater with speed, temperature, just stuck in second gear whenever he wants. What I have done is:
1. Changed transmission fluid and filter, using Mopar parts and ATF+3, the old fluid s pretty dirty though.
2. Disconnect battery for a while, retain the computer.
3. Swap the EATX relays (on right side of firewall), seems they are OK.
4. Changed TPS.
5. Get a set of input/output speed sensor from junkyard changed them on.
All those effort didn’t fix the problem. Using ignition switch method only gets 12 and 55 error code, which doesn’t really mean anything (?).

But I did find there are some noise come from alternator, which I’m quite sure the alternator bearing is failing. The charging system is working well, around 14.8v at idle. My concern is if the alternator fails intermittently which I may not notice while driving, would it cause transmission limp mode? Should it have an error code?

Many thanks advanced for any help.

[jsned]

Try using new speed sensors they are only about $20

[caravandrvr]

I have seen intermittent alternators wreak havoc on these complex electrical systems. I would suggest testing the voltage at idle with as much of a load as you can put on it. Turn on everything you've got - headlights, heater fan, flashers etc., and monitor the voltage over 20 minutes or so. If it keeps dropping then you'll know.

I concur that the sensor out of the boneyard are not to be relied upon, especially given their low cost. Perhaps they are still you issue. You can also suspect just about any other electrical part right up to the ECM.

[lon]

Updates:
Change alternator. No fix.
Change/Flush fluid again. No Fix
Clean solenoid packs harness. (Very dirty though) No fix.

OK, interesting happened here, change input speed sensor, Van instantly start “slip” while 2-3, 3-4 shifting, and get into limp mode more often, but sounds mostly happened if shift failed.

Went to AAMCO for a code scanning this morning. After road test, they said it’s binding which I thought it’s slip, the tranny are trying to apply two gears at same time. Also, the van can not power up their scanner, they said there are some communication problem, so didn’t get any code. They can find why the van can’t power the scanner for $80.00/hour, and don’t how long it’ll take.

Now what, Any ideas????

Would a TCM from a car/sedan with same size engine and tranny fits?

Thanks in advance.

[theFREAKnasty82]

that used to happen w/ older a-604 units, it would try to apply two gears at once. My suggestion is try having the TCM flash programmed.

[lon]

Put a 91 TCM on, 2-3shift is fine but lost overdrive. Took to AMMCO for computer scan, get code 53, 46. CVI 57,59, 56, 107.

Any suggestions?

[sandokana]

code 53-internal controller failure
code 46-charging system voltage too high-with this code engine light should be on

[lon]

no, there is not check engine light. Also, the ignition key method can't get any error code.

[itsme000]

Originally Posted by lon

I bought this 92 Plymouth Voyager couple month ago, but since I got it, it stuck in limp mode intermittently. No mater with speed, temperature, just stuck in second gear whenever he wants. What I have done is:
1. Changed transmission fluid and filter, using Mopar parts and ATF+3, the old fluid s pretty dirty though.
2. Disconnect battery for a while, retain the computer.
3. Swap the EATX relays (on right side of firewall), seems they are OK.
4. Changed TPS.
5. Get a set of input/output speed sensor from junkyard changed them on.
All those effort didn’t fix the problem. Using ignition switch method only gets 12 and 55 error code, which doesn’t really mean anything (?).

But I did find there are some noise come from alternator, which I’m quite sure the alternator bearing is failing. The charging system is working well, around 14.8v at idle. My concern is if the alternator fails intermittently which I may not notice while driving, would it cause transmission limp mode? Should it have an error code?

Many thanks advanced for any help.

14.8V is way high and will wreak havoc on your battery and lamps. It should be around 13.8V. Check for corroded grounding and/or failing regulator.