Questionput in another transmission and used the computer that came with it. drove it around after installation. no speed odomater and check engine light stayed on. changed computer to the one that originaly came with the car and after 60 miles of driving the only thing i have now is reverse and low?.everything worked for awhile up till that last 2 miles. is there a setting on the computers or is the trani bad?. this was a used trani.also can it be possiable that i have a bad computer?.how or where do i take it to get checked out?. Thanks for any help. Jim
AnswerHi Jim,
I'll take the questions in the order you listed:
The odometer and speedo depend upon the distance sensor which is mounted on the top of the transaxle housing extension and is an electical pulsation unit (3 wires). If the wiring looks o.k., then it may be that the gear on the sensor has been damaged when a former owner pulled out the right half-axle without first removing the sensor. I believe you can get a new gear at a dealer, or get the unit from a wreck, or use the one from your original tranny unit. The sensor is held on by a bolt, so just pull it out and inspect the gear for damage.
The check engine light is operated by the engine controller (computer) which is independent of the transaxle controller (computer) for the most part, though they exchange some information. The engine controller stores fault codes that you can readout with your ignition key. Just switch it:off-on-off-on-off-on within an elapsed time of 5 seconds. Then watch the check engine light to begin to flash, pause, flash, pause, etc. Count the number of flashes before each pause, make a mental note or write down the numbers. The last two sets of flashes will be 5 in each. Then take the numbers as recorded and pair them off to form two-digit numbers; thus the last number will be "55" which is the code for "end of readout". You can look up the codes at www.allpar.com/fix/codes.html Repeat the readout as often as you like to be sure to get the numbers correct.
Let me know if you need some help interpreting what they mean. So that will address any problem with the engine. You should get a code 15 (no distance sensor signal), for example.
The trans uses that sensor signal also, so correcting that might be of some help in its behavior. But, I can't be sure that will solve things. The trans running situation you have now is called "limp-in" mode, which it goes into when it sees one of about 30 possible problems. The trans computer also stores fault codes describing what is wrong with the way it sees the trans to be running. Unfortunately it doesn't have a self-readout capability, so you need to either go to a shop or Chrysler dealer that has a reader (it plugs into an outlet under the driver's end of the dash), or get a reader with a proper interconnect plug and that works with the Chrysler system. The codes will give you a reason for the limp-in but will not tell you exactly what to do to fix it. I have the manual for '92 for the tranny and can give you some ideas once you have the codes readout. I hope it is something with the valve body, fluid, internal pump, etc. so that it doesn't require removing the trans and tearing it apart. The unit is finicky about using only the Chrysler brand of fluid so if you didn't use that you might try changing out the fluid and replacing the filter. If you did that, you could also check to see if there is any significant amount of debris lying in the drain pans when you drop them. Such debris is a sign of damage, usually requiring the rebuild of the trans. according to the manual.
The computers do have the ability to accept upgraded instructions (usually with an accessory tool at a Chrysler Dealer shop). I think you would want to use the controller that came with the unit, because the controller instructions were no doubt modified from year to year, unless the used unit is also a '94 in which case they are probably interchangeable.
So let me know what you learn and feel free to ask any more questions.
Roland
