Question about 1997 Pontiac Grand Prix
1997 Grand Prix GT 'died' last week. Dropped new transmission in, car now goes into gear again. Now the problem is upon acceleration, for instance taking off from a stop light.. the car stalls and just barely moves past 10 mph without pushing the pedal to the floor. Once this is done the car flies upward to 50 mph and seems like it won't go any faster??? Before old transmission failed, the car would accelerate easily 0-60 mph in a lot less time. Also, ABS light stays lit & Traction control light will not stay on flashes back to 'Trac Off' setting??? Help!!! Thanks...
Hello! Although the symptoms you've described could be a result of quite a few things, I have a few questions that might help determine your problem.
1) What year/make/model did the new transmission come from?
2) Is the SES (Service Engine Soon) light on? Is it blinking?
3) Was this transmission a rebuilt or used unit?
- you could have a faulty TPS - or Throttle Position Sensor.
- you could have a problem with the input shaft piston being worn. (Hence the used vs. refurb trans question). Once the inner sealing area wears it can prevent the inner lip seal for the piston from sealing properly. You may find that revving the engine up will finally get the car to move and it will BANG into gear. This is because the pump in the transmission is working harder and moving more fluid thus allowing the added fluid to overcome the leak which prevented the clutch from either initially applying or staying applied. Another area of concern that causes this is a boost valve in the valve body, not near as common but it can cause this problem on a lessor scale.
- Trouble Code P0742 TCC Stuck ON:
When this trouble code is set the pcm will command max TCC and lock adaptive shifting. This code can be broken down into three potential problem areas as found to be common in the field.
1. This problem can be a mechanical problem. Possible causes of this could be a bad or stuck TCC switch that signals the pcm of current TCC operation. Another cause though not common is a stuck TCC switch or apply valve. If it is physically stuck in the wrong position it can cause the TCC to be stuck on all the time and even kill the engine when the vehicle is put into gear.
2. This problem can be found to be an electrical problem. If the wire from the TCC pressure switch to the pcm is grounded anywhere in the path it can throw this code. This could be a wire shorted inside the trans on the internal wiring harness or the actual engine wiring harness. If the wire is grounded the pcm thinks that TCC is on when it shouldnt be and will throw the code.
3. This problem can be a hydraulic problem. This is the most common cause of this code that I have found and stems back to a clogged TCC solenoid, not because it failed. Excessive debris in the transmission or a failing torque converter lockup clutch can cause the solenoid to have debris stuck inside and this causes a restriction in fluid flow through the solenoid. If the solenoid can not bleed off the pressure the TCC can be stuck on. If the wrong TCC solenoid is installed during an overhaul this problem can also arise as a late 4L60E solenoid is identical but does not operate the same and acts like a clogged solenoid. As mentioned in problem #1 a stuck TCC apply valve is a physical problem but causes a hydraulic problem because the fluid pressure will not properly bleed off because the valve is stuck in the wrong position instead of being able to move freely in the bore of the valve body.
Above are the common causes of this code, there are other possibilities but those are what generally causes the fault. A thorough diagnosis is the only way to determine what is really at fault and a new TCC solenoid should never be assumed as the actual problem until verified.
HTH - and thanks for using FixYa!
Posted on Feb 02, 2010
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Posted on Jan 02, 2017
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