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The dreaded P1860 transmission code


jhall

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Hi Gents,

My 2000 Deville is having fits.

Was driving it and started feeling bumping similar to a bad misfire. The service engine light came on, so I pulled codes and got the P1860.

I reset the code and took a test drive. Bumping occurs around 30 - 40 mph. Code was thrown again. Drove in 3rd gear and seems it's OK. Looks like the shift valve has failed - again. I don't see any visible problems with electrical connection to the transmission harness, but will check again.

At this point I am almost ready to toss in the towel. The transmission was repaired for the same issue by the first owner at 20K. I had same repair redone at about 70K. Car now has 145K and I don't look forward to climbing underneath, but I've got new rotors , brakes and CV shafts invested from earlier this year. GRRRRR!

I pulled the N* from a 1998 Deville and did time-serts plus transmission service. Was a great learning experience, but not crazy about doing major work like that on the 2000.

Body is in great shape (some paint skinned on front bumper corner) and interior is very good.

Just not sure if a repair at a shop is worth the car value - seeing value in the $1,000 to $1,300 range.

Any ideas? May be worth something to anyone that has the energy to drop the transmission.

Edited by jhall
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Look for a problem in the wiring harness and connector. There are too few miles for a genuine AC/Delco relay in a 4T80E to be giving problems.

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Just wanted to follow up and say that the 2000 Deville is done. Checked all connectors, reset code and drove it. Code came back - with rough shift - around 40 mph.

Since the repair is about the value of the car, I don't plan on keeping it.

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Too bad on the outcome. Strange that the problem keeps coming back. Can you post some pictures of the car?

Kevin
'93 Fleetwood Brougham
'05 Deville
'04 Deville
2013 Silverado Z71

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Do you suspect the rough shifting is due to the loss of shift-adapt after the P1860 is triggered? Are all shifts affected? Did you check for corrosion at the underhood 10 A transmission fuse (which also feeds the 1-2 and 2-3 solenoids)?

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