DTC code P1860
DTC code P1860
11-19-2007, 05:07 PM
11-20-2007, 09:42 AM
DTC P1860 is a type "A" DTC and indicates a torque convertor clutch pulse width modulation solenoid electrical problem. When set it disables shift adapts and inhibits TCC functions such as the lock/unlock when in 4th-OD. Possible flaky TCC-PWM solenoid.
11-25-2007, 03:32 PM
Thanks for the help. I have been unable to find a service manual for this Buick. Let me ask this....is the TCC-PWM solenoid something that is replaceable externally, or does it require removal or disassembly of the transmission. Also, is there a troubleshooting protocol I could use or is the troubleshooting simply to replace it? Is this a common problem. Let me add that I cleared the code but it returned after less than 50 miles and 4 to 5 starts. Thanks.
11-25-2007, 07:05 PM
Do you have the 4T65E autotransaxle, GM RPO Code M15?
There should be a GM factory service manual available from Helm, Inc. The autotransaxle is covered by other specialty manuals such as the one by ATSG. If you have a 4T65E the TCC-PWM solenoid is located under the side cover assembly. Not exactly easy to replace DIY. Engine/tranny has to be dropped down on the sub-frame assembly. See pic below for part location.
You could check the input voltage (12 volts) and ground/low to the solenoid via the main electrical connector. And check the resistance of the solenoid at the respective pins on the above connector. I have the value if you would like it.
11-25-2007, 07:19 PM
Thanks, BNaylor. This has reaffirmed my desire to keep my '99 Tahoe until the steering wheel is rotted....it's easier to work on than my wife's Buick. I paid for college wrenching, but this new stuff kills me. If the engine has to be dropped to get to this thing, and I must admit I have no idea where the main electrical connector is, I probably wouldn't be able to do anything to fix this at this point anyway. I suppose I will track the harness from the transaxle upward to simply check for damage, but beyond that I'll probably take it to the dealer. Any idea how much this repair should cost? Rock Auto sells the solenoid for about $35. Thanks again.
11-25-2007, 07:52 PM
Book time is about 5 hours plus fluid and gaskets.
11-25-2007, 07:57 PM
Assuming you have the 4T65E autotransaxle the 20 way electrical connector is located driver's side top. You should see it looking in. Gray connector and the only electrical plug going to the transmission. Twist counterclockwise.
Other than maxwedge's shop book estimate and just an example once the solenoid is proven bad and replaced the local AAMCO charges around $500-$600 including the part but cost will vary depending on where you live. Good luck.
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