Transmission 94 Plymouth Acclaim

Tiny
JOHGAN@TDS.NET
  • MEMBER
  • 1994 PLYMOUTH ACCLAIM
  • 4 CYL
  • FWD
  • AUTOMATIC
  • 145,000 MILES
We have a 94 Plymouth Acclaim that we use as a "beater" car. It has been very dependable. Yesterday, my husband was on the freeway and it dropped down into third gear and went for a while, then in dropped into first gear and wouldn't go above 20 mph. Is the car in "limp mode"? We have researched many possibilities including the TCM, the input/output sensors, and the adjustment of the cable. We are going to get started on the cable, before we take it to a shop. Do you think this car needs a new transmission, or that it could be a sensor, solenoid, or the TCM, or even possibly the cable to the transmission.
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Saturday, February 5th, 2011 AT 8:04 PM

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Tiny
CARADIODOC
  • EXPERT
If the symptoms occurred while driving at a steady speed that didn't require shifting to a different gear, suspect a sensor first. If the problem occurred during or right after a shift, typically an up-shift, suspect slippage in one of the clutch packs.

When the computer detects a problem, it keeps the transmission in second gear. That is "limp-in" mode that lets you drive slowly to a repair shop without needing a tow truck. Anytime it goes to limp-in there will be at least one diagnostic fault code in the Transmission Computer's memory. That code will lead to the circuit or system with the problem, not necessarily the defective part.

Caradiodoc
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Sunday, February 6th, 2011 AT 2:32 AM
Tiny
JOHGAN@TDS.NET
  • MEMBER
Thank you for your help. This is an automatic transmission. He was in stop and go traffic, the traffic opened up and he began to accelerate and it wouldn't go (he thinks into fourth). Today we worked on it and there was no check engine light or service engine light. We disconnected the battery for a bit (to see if it was a glitch - based on info we read from others) We contact sprayed the input/output sensors. The fluid is fine. We brought it back out and it ran through the gears great for 3 miles and then went back into the "limp mode." My husband was rear-ended two days prior to this occuring. He was stopped on the freeway and the man who hit him was going 20 to 30 mph. Could this have caused any of this, because we have really had great luck with this little car with a couple of other small issues. Thank you so much for your help.
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Sunday, February 6th, 2011 AT 2:53 AM
Tiny
CARADIODOC
  • EXPERT
Rear ending shouldn't affect it but you will never know until the cause is found.

The fault codes will be in the Transmission Computer (EATX). The Check Engine light is for the Engine Computer (PCM). Many aftermarket scanners won't access the Transmission Computer. To reset the computer from limp-in, all you have to do is turn the ignition switch off and restart the engine.

Disconnecting the battery will cause two problems. First, that will erase all of the diagnostic fault codes that are currently in memory. Those are the single biggest clues to the cause of the problem. When they are erased all of that valuable information is lost. Now you'll have to drive the car again until the problem acts up and hope all of the pertinent codes set again.

The second problem is the computer knows how much fluid it takes to apply each of the four clutch packs. That changes as the clutch plates wear. Unlike older transmissions that gradually developed sloppy shifts over a period of more than 100,000 miles, your computer compensates for that wear. It continually updates the timing of how it engages one gear before it releases the previous one. That results in a nice crisp shift that covers up any clutch wear until the day comes when it can't update anymore. That's when the slippage occurs. When the computer detects that slippage, it sends it to limp-in.

All of that updated shift schedule information remains in the Transmission Computer's memory. When the battery is disconnected, as when replacing it, that information is lost. The next time you drive the car, it starts out with the values programmed in at the factory. Typically it takes about a dozen shift cycles from first gear to overdrive, and a good two to five miles to relearn the characteristics of any clutch pack wear. Until that happens, it could shift real sloppy or it could shift real hard like a race car. Now you have two problems. The computer is requesting clutch engagement at the wrong times coupled with whatever is causing it to go to limp-in. The combination can result in the wrong fault codes being set.

The solution now is to have the fault codes erased with a scanner that can access the transmission computer. That should be done after the car is driven long enough to update the shift schedules. Erasing those codes won't affect the rest of the updated memory. Next, drive the car again until it goes to limp-in. Then you can have the codes read again and they should be accurate.

Caradiodoc
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Sunday, February 6th, 2011 AT 3:59 AM
Tiny
JOHGAN@TDS.NET
  • MEMBER
Thank you again for your help. We are calling a mechanic tomorrow (Monday). I will leave a follow-up on this web-site to let you know what happened. (It might take a week to find out). We have never used a site like this and it has been very informative and helpful prior to seeing a repair specialist.
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Sunday, February 6th, 2011 AT 3:36 PM
Tiny
RIVERMIKERAT
  • MEMBER
Any word on this Johgan?
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Wednesday, January 25th, 2012 AT 7:11 AM

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