torque convertor lockup problem

I have a 96 Buick Regal 3.1 with 106k on the odometer. When driving on the highway at speed 65 and over, the lockup will not work. I can tell because of the rpms don't drop slightly. Then I get a check engine light with code 1870. I was wondering if anyone can shed some light on this?

DTC P1870 in a 4T60E transmission is a Transmission Component Slipping fault. Excessive TCC slip has been detected when the torque convertor should be engaged.

When was the last tranny service performed. ATF and screen filter?

I recently changed the fluid and filter, the old fluid did not look too bad. This problem hapens after about 10 minutes of highway driving.

the bad news 96's were terrible at loosing converters. The converter has more than likely gone south.

I recently changed the fluid and filter, the old fluid did not look too bad. This problem hapens after about 10 minutes of highway driving.


You can unplug the comverter or pull it's fuse if it has one, and still use the car as you normally do. You will use a little more fuel but it won't do any damage to the vehicle. I drove a Olds for 75k miles with the converter unplugged.

You can unplug the comverter or pull it's fuse if it has one, and still use the car as you normally do. You will use a little more fuel but it won't do any damage to the vehicle. I drove a Olds for 75k miles with the converter unplugged.

His Regal has a 4T60E RPO M13 autotransaxle. You cannot pull a fuse for just the torque convertor without losing all shifting.

The TCC lock/unlock commands go through one umbilical connector. Again, removing it will disable all shift functions not just torque convertor.

His torque convertor is not locking so I do not know what good disconnecting it will do. It sounds more like a valve body related problem with the TCC or TCC-PWM solenoid. It would be different if the torque convertor was constantly engaged, then trying to disable it would make sense.

did you clear the codes/reset the ecu/ecm/pcm? just to see if the code will return?

easy to do & worth a try <shrugs>

One thing I noticed that the problem occurs when the tranny is hot. I had an external cooler but I guess it was not doing its job. So I went to the junkyard and I set out to find the biggest tranny cooler that I could find. I ended up finding a small ac condenser about 22"x12". I flushed it out and cleaned it up. It was awkward fitting it in but I hooked it up. Then I took a long drive about 300 miles on the streets and freeways and the lockup worked like a charm :D .... at least for the moment. I have no clue as to how long it will work, who knows. At least I learned something.

did you clear the codes/reset the ecu/ecm/pcm? just to see if the code will return?

easy to do & worth a try <shrugs>

I would scan the codes and clear the codes with the my actron scanner but they would allways pop back up. I just wonder how long this tranny will last.

You've got nothing to lose at this point in time since it looks like a solid problem but have you tried any tranny additive? Lubegard or Seafoam?

Also, find the tranny umbilical cable. Should be at the top of the driver's side of the tranny. Remove it. Check for corrosion, etc. and then reseat.

around town it can last for a while but get out on the hiway using OD on a hot day its just a matter of time. like I said earlier 96 was a bad year for TC on GM cars they always seem to fail.