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Followup To
Question -
I have a 1996 Chrysler Concorde LXi that gets stuck in "Limp mode" - no other problems or symptoms. This started after a tranny fluid change at a local 15 minute place I will not mention in case it is not their fault. If I restart the car when warmed up that usually sets shifting back to normal. I paid to have a DRB II scan done and it came up with a 21 error code - speed overdrive pressure switch. Need to know if this is something I can replace/repair or is this a dealer only? Dealer said I had four codes but deleted them and took it out for a test drive and got the #21. I am told "the code doesn't mean there is anything wrong with the switch" and for $400 the dealer will drop the pan and test it for me. Anything beyond that is extra and they won't know until they drop the pan. What do you recommend? Thank you for any help.
Answer -
Hi Gene,
I made one important error this morning:
The transmission auto shutdown relay where I suggested that you apply 12V by jumper to pin D is located diagonally across the power distribution center from where I described it, i.e., it is at the outboard-front of that center and it might be labelled relay #7. The D pin is still the one at the rear of the socket (where the four pins are arranged in a square as it were (front, back, left and right). So I hope that you haven't been thrown off by this mistake. The relay #4 I erroneously pointed you toward is the one for the engine automatic shutdown relay, which also uses its pin D for power to be supplied but to very different systems. So no damage would have been done, just no response to those switch tests, and maybe some other things clicking (like the fuel pump!) when you did the jump. My error was caused by some inadequate labelling of the '94 Chrysler shop manual which was early in the history of the LH body line.
Roland
Hi Gene,
I would suspect that the fluid that was used by the local 15 minute shop didn't mix well with the fluid that was in your trans because I have heard frequently from other owners that the fluid needs to be the MOPAR brand 7176 or there may be problems developing thereafter. When you "change" the fluid only a fraction of it is actually changed, unless you go all the way and have the unit flushed which also removes the fluid from the torque converter and the cooling unit and lines that run to the front of the car. So you end up with a mix. Did you discuss that issue with the dealer and did they think that could be the reason for the concurrent start of the problem with that immediately previous service?
I looked up the 21 code and it mentions the possible causes as: low/high fluid level in the trans (which to me might also be mimicked by a bad fluid mix);
short/open in OD pressure switch;
solenoid pack internal problem;
internal transmission problem (the bad one, if true);
electrical problem in the 60-way trans plug at the controller (pin 9 for the OD stich);
trans controller failure.
The access to the switch does involve removing the valve body which requires the pan drop so that is correct.
But you might want to get a price on a trans flush and thus complete fluid replacement. And you could remove the 60-way plug at the trans controller and compare the resistances shown on three of its pins (9, 47 and 50) to oneanother as these are three separate switch circuits which should be identical I believe when the car is shut off. I would measure the resistance between each of those pins and ground (- post of the battery, or the engine block ground strap) and also to pin D of the automatic trans shut down relay in the power distribution center under the hood (square box between the battery and the strut tower, the relay is #4, at the rear-inboard corner of the box, remove the relay and use your meter's probe on the relay pin socket which is closest to the rear of the box). If all readings for the 3 pins were not identical at those two separate points it would suggest to me that there is indeed something wrong with the OD switch in the solenoid pack/valve body. If they were identical I would lean toward the fluid flush first. Of course the OD switch might not be good and it wouldn't show up in a resistance issue. So, you might try putting 12V by jumping a wire from the battery + post to the pin socket of the trans shutdown relay where you tested the resistance, and then ground pins 9, 47 and 50, one at a time and listen for a click to come from the trans solenoid box. If they all clicked, that would be a verification of the switch being o.k. (47 is the kickdown pressure switch, 50 is the low/reverse pressure switch, and 9 is the OD pressure switch).
So that is my "amateur mechanic" suggestions for you. Please let me know what you learn and how this get resolved so I and others with a similar code will learn too.
Roland
Thank you Roland. I will do what you said and post my results back to you and your readers. In the meantime, I did ask two dealers and a private shop about flushing the tranny fluid and they all said they would do it but not by conventional flushing. They would "have to drop the transmission to drain all the fluid out of the torque converter." Otherwise, they claim, more damage will result to the transmission, especially, the torque converter.
I changed the tranny fluid to ATF+4 after this happened. It was late when I started so I left the pan off overnight. It was still trickling out fluid the next morning. Instead of 5 quarts, the tranny drained almost 10 quarts of fluid. How much is in the tranny and converter total? I was told 13 quarts. Is this right?
Are the service shops right about not using a flushing/drawing machine on the tranny? I was going to drop pan like before, Replace filter/gasket and reset pan. Fill as before - hopefully 10+ quartz of ATF+4 (I will buy from Dealership at $28/gallon - steep but the right kind). Remove return line to tranny and start engine. Bleed fluid in drive until color changes to new fluid red. I won't do this until I hear back from you. Nothing worse than making matters worse if this is not the way to purge the old fluid out. Thank you in advance,
Gene
AnswerHi Gene,
I checked the capacities and the "trans and torque converter" sump is listed at 9.9 quarts so you must have gotten a good drain. That figure may not include the torque converter entirely nor the cooler and lines, but you did get a pretty good dilution of the fluid from the quick lube, if that is indeed the problem. If you assume the whole thing is 13 quarts and the quick lube put in 4 originally what you should have now is less than a 15% mix of that fluid. On that basis my inclination would be to do the electrical testing first and if all those pass then I would probably just do the fluid drain again which would be alot less expensive than having the shop "drop the tranny" which is not cheap. If you can drain another 10 qts out you would have it below 5% which would be very hard to believe would cause a problem. And if they used ATF of the type that is equivalent to Chrysler brand it even adds more to the argument to not let them touch the tranny. That removal process is not without its risks too. Maybe it will be found by the testing to be something that just involves the valve body/pressure switch (which will require a partial drain anyhow) or if not then just doing another 10 quart gravity drain will do it.
Roland
