Jump to content
CaddyInfo Cadillac Forum

Help!! Code P056


Recommended Posts

Hello, I have a 1994 SLS and lately the car has been doing a little rough shifting. It does not happen all the time, only once in a while. When changing gears, you can sometimes feel a pull. I checked the codes since the service engine soon light is on, this is what I got P056 and the descrition I found for this code is the following, Transaxle Input Speed Sensor Circuit Problem. I have the Chilton book, but can't find were this sensor is located or how it's replaced. Can anyone help me??? Images would be appreciated.


Link to comment
Share on other sites

The input speed sensor has been discribed as "the $20 part, $2000 deep inside the trans". You won't find it in a Chilton manual nor will you find it without disassembling the trans.

Link to comment
Share on other sites

Hi Caddyjag,

I had the same problem couple years ago. I ended up using this stuff from Napa called TRANS- something (can't remember the exact name) but it did the trick. The way it works: You just pour it in with the tranny fluid (make sure you siphon out equal amount of tranny fluid beforehand). Next you drive the car like a madman, making sure the the car goes through many shifts for about 60 miles. Then you drain the tranny fluid and at this time cleaning or changing the filters is a good idea. Close her back up and add fresh tranny fluid. That was 2 years ago and my tranny still feels smooth.

Now this may not be your problem and i would check to see what some of the other fellers have to say.


"Burns" rubber

" I've never considered myself to be all that conservative, but it seems the more liberal some people get the more conservative I become. "

Link to comment
Share on other sites

Here is a search result from p056, (30-days and older). It has pictures, etc and there were other relavant posts.


I would guess that this tranny speed sensor is probably a non-contact, magnetic flux device that counts the chain drive teeth.

These are used a lot in industrial equipment to measure motor rpm and virtually any other low or high speed gear application - so they are fairly relaiable. Heat, oil, dirt etc - should not be a factor - unless heat, vibration or something else is changing the distance between the pickup head the gear teeth or interfering (metal shavings :( ).

These type of pickup devices generate a very weak electrial pulse that can be subject to interferance. Have any wires been re-routed lately or new electrical equipment installed? <_<

The speed sensor may be comparing road speed to tranny speed to determine slip etc. When its signal quality is doubted, the tranny may default to a "protective mode", meaning stouter shifts - and perhaps even 2nd gear starts and traction/stability disabled (since it is part of the overall engine/tranny/suspension confidence network).

It is interesting that numerous posts have reported that it can fail, recover after some "differant type of driving" and then be OK for some period of time.

Good luck :)

Add power to leave problems behind. Most braking is just - poor planning.
Link to comment
Share on other sites

The P056 error code is a fairly common error, of the Transmission Speed Input Sensor.

It is a small low cost part, deep in the transmission. If you do not have constant hard shifting, ignore it. The error is most often an intermittent problem.

One source of the error has been pretty much identified. The spark plug wires and/or the heater motor.

The wire loom that carries the transmission sensor is located at the fire wall, behind the spark plug wires. The wires have often been moved from their original location when the spark plugs have been serviced or for some other repair in that area.

Organize the spark plug wires in a neat manner. Pull them toward the coil pack and secure them with nylon tie strap(s).

Move the small wire loom at the fire wall as far away from the spark wires and the heater motor as you can and secure it with nylon tie strap(s).

I use black tie straps and they are pretty much invisible.

Clear the codes and hopefully it will stay away.


Drive'em like you own 'em. - ....................04 DTS............................


Link to comment
Share on other sites


This topic is now archived and is closed to further replies.

  • Recently Browsing   0 members

    • No registered users viewing this page.
  • Create New...