Is my car stuck in limp mode?

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mysterymau0521

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Colorado
Vehicle Details
1997 Thunderbird LX 4.6L OHC
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97 Thunderbird lx 4.6l with a replaced (used) 4r70w transmission

A bit ago I lost my first gear and received a code for the shift solenoid. I also didn't have 4th gear and the O/D OFF light was flashing. I took it to the shop because it was still under warranty. The replaced the solenoid and that did not help. they think it may be the valve body but I have no idea (I have no knowledge of transmissions). I recently got it back and it is doing the same as before. I also still have a misfire in cylinder 4. I am going to replace the intake manifold as I definitely have a vacuum leak under there. Do these cars have a "Limp Mode" and could any of these issues be causing that?
 
The transmission will stay in 2nd gear in limp mode. At first glance it sounds like there's probably a wiring fault in the harness for the trans; the solenoids themselves rarely go bad and when there's an electrical code for them it's usually harness related. With 30 years of heat cycling on the wiring, if it was disturbed enough during replacement it could have been just enough to cause an issue.
 
Correct; limp mode is 2nd gear only. It is the only gear where both shift solenoids are off, therefore when electrical gremlins plague the transmission it is the only gear available when the manual lever is in "D".

Here's a brief chart that shows the behavior of the shift solenoids for each gear:

Gear​
Shift solenoid 1​
Shift solenoid 2​
1​
On​
Off​
2​
Off​
Off​
3​
Off​
On​
4​
On​
On​

If you don't have 1st or 4th, it's a problem with shift solenoid 1 - again, most likely the wiring, rather than the solenoid itself.
 
theterminator93 said:
The transmission will stay in 2nd gear in limp mode. At first glance it sounds like there's probably a wiring fault in the harness for the trans; the solenoids themselves rarely go bad and when there's an electrical code for them it's usually harness related. With 30 years of heat cycling on the wiring, if it was disturbed enough during replacement it could have been just enough to cause an issue.
Click to expand...
do you know where i could buy a trans wiring harness?
 
theterminator93 said:
Correct; limp mode is 2nd gear only. It is the only gear where both shift solenoids are off, therefore when electrical gremlins plague the transmission it is the only gear available when the manual lever is in "D".

Here's a brief chart that shows the behavior of the shift solenoids for each gear:

Gear​
Shift solenoid 1​
Shift solenoid 2​
1​
On​
Off​
2​
Off​
Off​
3​
Off​
On​
4​
On​
On​

If you don't have 1st or 4th, it's a problem with shift solenoid 1 - again, most likely the wiring, rather than the solenoid itself.
Click to expand...
thats odd because i definitely do have 3rd gear
 
It's not in limp mode; it's just a fault with SS1. Troubleshoot the harness to isolate the break. It may be in the trans harness or it may be in the vehicle harness that comes through the dash into the trans tunnel.

Start by measuring the resistance from the trans harness connector. If it's infinite there's an issue in that section; replace the damaged section of wire there, or narrow it down to bad connector or the like. If resistance is 0 or near 0 it may be shorted. If it's within spec, repeat the tests from the PCM to the trans harness connector with it connected. If there are issues you know the trans harness itself is fine and the issue lies with the vehicle harness between the PCM and trans (or the junction) and that section needs service.

Check the tech articles section for Jerry's Thesis; it lists the pins you need to test as well as the resistance values. Having the factory EVTM will make it easier still.
 
Last edited:
MadMikeyL said:
Your comment that the trans is still under warranty makes me wonder if they put a 98+ trans in your 96. The connector pinout is different, and the later trans will plug in, but won’t work properly.
Click to expand...
mine is a 97 not a 96 and it was working fine for a while. it only started after i replaced one of my 02 sensors
 
Sounds like you have a loose connection or broken wire in there. Those can be difficult to troubleshoot, I find it best to put an ohm meter, one lead on each end of the wire then jiggle and squeeze the wires in snap sections watching the resistance. Hopefully you’ll see a chance and can narrow down a small section of wire that’s the culprit.
 
What color is the plug on the pass side of the trans? The car wiring plug is white, but I mean the plug it plugs into, mounted to the trans.
 
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