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4l80 and the limp mode of death

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Old Apr 24, 2018 | 10:25 PM
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Default 4l80 and the limp mode of death

Trans is staying in 2nd gear, and doesn’t shift. Checked codes and I’m getting solenoid a and solenoid b are both open to ground. This is an LS swapped car using a speartech harnes. Seems odd both would not work. Checked harness going into it and and all looked good. Any ideas are greatly appreciated as I absolutely hate electric problems.
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Old Apr 25, 2018 | 08:08 AM
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2nd gear is default for 4l80e with no power. Check fuse for trans. Use a multimeter and make sure you have power down to the trans.
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Old Apr 25, 2018 | 09:39 AM
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Originally Posted by MaroonMonsterLS1
2nd gear is default for 4l80e with no power. Check fuse for trans. Use a multimeter and make sure you have power down to the trans.
Which pin should I check? Can I do it key on or does it have to be running? Thanks
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Old Apr 25, 2018 | 12:05 PM
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1994 and up.
Pink/Black or Pink or Brown is key on power Pin E

Everything is powered up with the key on, it's all switched on the ground side. And the ground signal comes from the PCM. So It could be a missing ground pin in the PCM connector. Somehow the PCM detected no ground.
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Old Apr 25, 2018 | 12:06 PM
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Last edited by MaroonMonsterLS1; Apr 25, 2018 at 12:07 PM. Reason: pic link broken
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Old Apr 25, 2018 | 12:09 PM
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Originally Posted by Jays_SSZ28
1994 and up.
Pink/Black or Pink or Brown is key on power Pin E

Everything is powered up with the key on, it's all switched on the ground side. And the ground signal comes from the PCM. So It could be a missing ground pin in the PCM connector. Somehow the PCM detected no ground.
Each solenoid is grounded separately. That's why I pointed to a power issue not a ground issue. The ground for both solenoids would need to fail to have neither of them work
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Old Apr 25, 2018 | 01:08 PM
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Originally Posted by MaroonMonsterLS1
Each solenoid is grounded separately. That's why I pointed to a power issue not a ground issue. The ground for both solenoids would need to fail to have neither of them work
Grounds for all the transmission components come from one driver in the PCM. So if the ground for that driver is missing, nothings going to work.
Theres a reason the PCM detected "open to ground".
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Old Apr 25, 2018 | 01:24 PM
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This is verification that I'm not just guessing. Pink is key on power to everything. The circuit is completed by grounding the other side of the solenoids, etc, inside the PCM. All related grounds internal to the PCM usually tie to one pin that grounds to the engine block.

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Old Apr 25, 2018 | 01:26 PM
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Originally Posted by MaroonMonsterLS1
This is the internal plug and wiring colors, they are different than whats outside.

This is the external harness.



Last edited by Jays_SSZ28; Apr 25, 2018 at 01:31 PM.
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Old Apr 25, 2018 | 02:50 PM
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I’ve got power at the trans plug. I called Justin at speartech and we went through every pin and everything is where it should be. He said for the codes I’m throwing check wires 24 (grey) and 44 (dk blue) for continuity between the plug and tcm pin. Everything checks out. I’m guessing it’s the harness in the trans?
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Old Apr 25, 2018 | 03:07 PM
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Originally Posted by Mr.Bu
I’ve got power at the trans plug. I called Justin at speartech and we went through every pin and everything is where it should be. He said for the codes I’m throwing check wires 24 (grey) and 44 (dk blue) for continuity between the plug and tcm pin. Everything checks out. I’m guessing it’s the harness in the trans?
We should start at the beginning.
Did you ever drive this transmission?
What year is it?

You could try this test to get a definitive answer on where the problem is. The transmission or the wiring.

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Old Apr 25, 2018 | 05:50 PM
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I think I got it figured out. Connector had fluid in it, causing a short. I’m replacing the internal harness.
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Old Apr 26, 2018 | 03:12 PM
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Trans shifts, internal harness was the culprit. Thanks everyone for the help!
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