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00 Grand Prix GTP lost D, 2, and 3
michaelstarr84
Member Posts: 18
My GTP will not shidt into D, 3, or 2. I do have R and 1. While driving, in can manually upshift at the proper speeds all the way into D and drive with no problem. But when i stopped, i lost all forward gears and had to be towed. I then changed the 2 shift solenoids, the TCC, the PCS, and the main pressure switch ssolenoids. Same. Only 1 and R so i road tested it and got the same result. I then removed and rebuilt my transmission with a level 2 master kit, replaced the torque converter, and replaced the BROKEN forward band. I was so pleased with the find and the repair. Its all back in. Same thing. 1 and R only. Im baffled. Anybody? Anything?
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Comments
Do you have battery voltage to the PCM on pins 4 light green and 44 yellow /black of C1 and pin 78 brown of C2 with the key on, engine off ? If so, and you manually ground pin 4 light green at connector #1 does the transmission then shift to second gear?
P0717 is the input speed sensor circuit, and P1860 is the TCC pulse width modulated solenoid circuit. If you don't have power to the PCM on pins 4 and 44 of C1 it really should be setting P0753 and P0758 as well, you might want to double check to make sure that you were making a good connection when you tested those two pins.
Carefully inspect the transmission wiring harness connector, and the transaxle connector to make sure that all of the pins are properly in place and not damaged.
So from the beginning with this code as if nothing else has ever been done.
P0724 TCC system stuck on.
We instruct the techs to research what the code means and how the PCM runs the test. There is a switch inside the transmission that grounds a 5v signal from the PCM when the TCC is turned on. Fluid pressure opens the switch when the TCC is turned off.
At this point compare that description to what it feels like when you are driving the car, is the TCC applied and the torque convertor not able to give you multiplication or is it not applied and working normally?
With a scan tool a tech would be monitoring the TCC slip speed and using bi-directional controls to help interpret what the system is doing.
The TCC apply switch is the yellow wire at the PCM connecter pin 63 of C2. Pin U of the transmission connector. A tech might find themselves having to confirm if the PCM is reporting the true state of the circuit and have to manually prove when it is grounded or not.
Here is GM's explanation of the circuit. "The TCC release switch is a normally-closed switch. When the TCC is released, TCC release fluid pressure opens the TCC release switch which opens the TCC release pressure circuit. When the voltage on the circuit is high (switch open), the PCM recognizes that the TCC is no longer engaged.
If the PCM detects that the TCC release switch is closed when the TCC is commanded OFF, then DTC P0742 sets"
Update: amperage test produces audible solenoid clicks at pins 4 and 44 of C1 and also pin 78 of C2. Getting zero results from pin 63 of C2
The greatest irony in all of this is rebuilding the transmission, that's easy. If you were working as a tech you would not have been paid for any time that was invested beyond what the rebuild paid and every possible insult, or slap in the face that someone could have tossed your way would have been used to belittle you for not solving the electronics issue in a matter of minutes. Electronics diagnostics like this are quite often anything but easy. That's even more so when some of it requires disassembling the transmission in the car especially if there is still doubt as to whether the failure is inside or external of the transmission. There are ways to prove where the circuit failure is most of the time but they can be labor intensive and with all of the pressure that is getting placed on the tech at that time they literally get trained to simply avoid this work. That's something that the consumer is starting to recognize the result of thirty plus years of mismanagement in the trade. They don't know what has caused it, they just know that they can't find the techs that they need easily.
One thing that is still questionable is your statement that the yellow wire is grounded inside the harness. If it really is then it is not likely to be the only affected circuit. The bypass is OK to a certain degree and would be more advisable when you have an open wire, but not a grounded one. Time will tell but you might need to remove, disassemble and repair the harness.