Transmission

[skidude]

Ok guys need help with this one. Engine light is on and loss of power. Poor take off and revs 3000 rpm at 100km. Also can't get the key out of ignition. Bag on botton of steering column and key comes out. Put it back in and same problem. Had this once before and replaced igbition switch. Worked for a year and it's back again. I'm thinking either I need another ignition switch or some other part near the ignition switch. Forgot to add it's a 1997 jimmy 4x4 SLS

[blazee]

Go get the codes scanned then come back and post them. Does it shift hard between 1 - 2 and when you put it in gear? Have you tried manually downshifting to get a better take off? Do you have a remote start?

[skidude]

Found the problem. It was the ignition switch.

[blazee]

Yeah, kinda what I figured. Hopefully you got the updated switch this time.

[herkyhawki]

Blazee,
Can you tell me why you asked about remote start ?
I'm having a similar problem in a '95 and I do have remote start. What's the connection?

[blazee]

The ignition switch causes shift problems, because it doesn't supply power to the tranny on circuit 1020. The same problems can be caused by an aftermarket remote start that was either connected wrong, or has developed a broken connection causing it not to energize circuit 1020 when the device is used. A problem with the remote start is easily diagnosed, if the problem occurs only when the remote start is used and functions normally when started by the key. A problem with the ignition switch or remote start not supplying power to circuit 1020 will set one or all of the following codes: P0740, P0753, P0758, P0785, and P1860. This condition will put the tranny in "limp home mode". This mode raises fluid pressure to maximum causing hard shifts when going into reverse and hard 1-2 shifts. After the initial shift into 3rd the tranny will stay in 3rd regardless of speed, this includes take-off. Taking off in 3rd can easily be mistaken as a loss of horsepower or tranny slippage. Leading you to believe the damage is far worse than just a simple loose wire. That is how some people really get screwed by tranny shops.


Another thing that can cause shift problems is an after market air intake with a filter that has been excessively oiled. The oil that is used can be transferred to the Mass Air Flow sensor. This will cause the Grams Per Second reading to be low, which can cause poor engine performance and transmission problems such as slipping and damaged clutches or bands.

[Schrade]

I've got this one too, skidude - locked key, and the limp home 3rd gear mode, w/remote start (relationship unknown), plus 4X4 mode prob's...
Whatcha got now - what was the fix?

[blazee]

Originally Posted by cbec1999

I've got this one too, skidude - locked key, and the limp home 3rd gear mode, w/remote start (relationship unknown), plus 4X4 mode prob's...
Whatcha got now - what was the fix?

For 98-01 check for power on fuse 11:

If there is no power, that means that there is no power going to the transmission solenoids. The most common cause is an improperly installed remote start. This can also be caused by a bad ignition switch. Inspect all the remote start wiring and verify that the circuits are energized when the remote start and the key are used, if one fails to energize the circuit you have found the problem.

If there is power at the fuse, inspect the wiring from the fuse to the transmission for problems.

[dchrist]

I have this same problem - is it the actual key switch? If so what is the avg. cost and what is the difficulty to replace?

Your help is greatly appreciated...!!!

[skidude]

The part was the switch including part of the harness. Pretty simple to replace unless you have a car starter. If you do get ready for some splicing. Switch cost me 166.00 canadian from dealer

[1996GMCJimmy]

Originally Posted by blazee

The ignition switch causes shift problems, because it doesn't supply power to the tranny on circuit 1020. The same problems can be caused by an aftermarket remote start that was either connected wrong, or has developed a broken connection causing it not to energize circuit 1020 when the device is used. A problem with the remote start is easily diagnosed, if the problem occurs only when the remote start is used and functions normally when started by the key. A problem with the ignition switch or remote start not supplying power to circuit 1020 will set one or all of the following codes: P0740, P0753, P0758, P0785, and P1860. This condition will put the tranny in "limp home mode". This mode raises fluid pressure to maximum causing hard shifts when going into reverse and hard 1-2 shifts. After the initial shift into 3rd the tranny will stay in 3rd regardless of speed, this includes take-off. Taking off in 3rd can easily be mistaken as a loss of horsepower or tranny slippage. Leading you to believe the damage is far worse than just a simple loose wire. That is how some people really get screwed by tranny shops.


Another thing that can cause shift problems is an after market air intake with a filter that has been excessively oiled. The oil that is used can be transferred to the Mass Air Flow sensor. This will cause the Grams Per Second reading to be low, which can cause poor engine performance and transmission problems such as slipping and damaged clutches or bands.

Hi Blazee, what you state in this message is exactly what happens with my tranny of my 96 Jimmy SLT 2wd. P0753 and P0758 come up and it seems like my tranny starts up in third. I've trid to manually downshift it to first to get a better take off and it works. Also, i've noticed that my tranny red fuse (10amp) gets blown. This has happened about three times in the past but all I do is replace the red fuse with a new one and clear the codes at my local autozone and then its all fine.

The funny things about it is that all fo this starts right after i've replaced my trannys fluid. Also, I ve got an alarm installed on it with a Switch kill on it...im thinking, could there be a false contact causing a short circuit?

Can you give me any other advice? Thanks.

[ZL1power69]

I had a similar issue last month and it could be the same problem with your trans. I had a po 758 i think. Very common problem, especially if the trans has either been neglected or if you did a fluid change and caught something while reinstalling the pan. There are two solenoids at the rear of the valve body. What happens is that the solenoid electrical connection fails and the soleniod doesn't operate. This was the case with my truck and solenoid b (A controls reverse, B controls foward gears). The TCM defaults to only 2nd and 3rd gear with reduced pressure. Basically you have no 1st or overdrive and it feels like your driving a manual trans with a worn out clutch. You need to drop the pan and replace that solenoid, b should be the one on the right. To confirm its bad, pull the solenoid, put it on a bench and jump 12 volts to it. If you can't hear it click, then its bad. After you replace the solenoid and put the filter and pan back up, refill with dextron III fluid (go through the gears, add more fuild, take for a drive, add more fuild). The code should clear itself. Hope this helps you.
BTW, this thread is almost 3 years old. please refrain from posting old threads in the future.