Hello I own a 99 corvette and for several months I keep receiving code P1860. I have done reasearch to discover that this code is indicating an error with the Torque Converter Clutch Pulse Width Modulation Solenoid Valve. Since the error is indicating a short somewhere in the circuit, I have checked many engine grounds and electrical connections. Specifically G120 that the PCM should use to ground the solenoid but the code keeps returning. I have even taken the car to a transmission shop to replace the solenoid but the code keeps returning. Any help or knowledge in fixing this code would be greatly appreciated. Thanks!

 

Check out this GOOGLE search and look at this schematic and check the wires to and from the transmission at the main connector. You may need to drop the pan and check the internal wire harness inside the trans.

https://www.ls2.com/boggs/a4/DTC%20P1860%203.8.htm

Let us know what you find.

Bill

 

Bill,

I have replaced the solenoid inside the transmission but still no luck. Any other ideas? Do you know the path the physical ground wire takes? Is there a specific connector I should check for corrosion or bent pins?

Thanks

 

Still getting the code this weekend. Any other suggestions would be greatly appreciated.

 

OK let's get you a fix...for a 1999 Model Year.
Note it is very important that there are NOT any other "P" codes posted to the DIC and the only code is the "P1860". If you DO have other "P" codes, post them up as this will have a different troubleshooting path.
Circuit Description
The torque converter clutch pulse width modulation (TCC PWM) solenoid valve controls the fluid acting on the converter clutch valve. The converter clutch valve controls the TCC application and release. The solenoid attaches to the control valve body within the transmission. The solenoid receives ignition voltage through circuit 339. The powertrain control module (PCM) controls the solenoid by providing a ground path on circuit 418. Current flows through the solenoid coil according to the duty cycle (percentage of ON and OFF time). The TCC PWM solenoid valve provides a smooth engagement of the torque converter clutch by operating during a duty cycle percent of ON time. When the PCM detects a continuous open or short to ground in the TCC PWM solenoid valve circuit or the TCC PWM solenoid valve, then DTC P1860 sets.
Conditions for Running the DTC •
The system voltage is 8-18 volts. • The engine speed is greater than 300 RPM for 5 seconds. • The engine is not in fuel cutoff. • The PCM commands first gear.

After reviewing the system schematic two (2) connectors caught my attention..Connector C140 and Connector C144, (boxed in red on the below schematic).
Both Connector C140 and Connector C144 are located in the battery compartment zone...
Recommendation>
First, simple> Inspect the ENG IGN 1 fuse to see if it open or blown...Post up if this fuse is, in fact, open or blown...?
Next.
Remove the battery AND battery tray and locate and disconnect both Connector C140 and Connector C144 and inspect for corrosion on the pins, pay specific attention to the following pins;
Connector C140> Pin "E" Pink Wire.
Connector C144> Pin "V" Brown Wire
Post up your findings as this will dictate further trouble shooting steps.






Cheers,
Goose

 

Thanks for the advice. I checked the C140 and C144 connectors.
both connectors didn’t have any indications of significant corrosion. I plugged the connectors back together and drove the car and the P1860 code returned. Any other ideas? Thanks

 

Great news on the connectors. Time to start performing continuity checks on the wires (power/ground) for the solenoid looking for opens and shorts…with the battery removed from the car….



My first continuity check would be as follows to check the wiring from the battery compartment thru the transmission solenoid and back the battery compartment looking for an (open/short) in the wiring.

Example to start the wire checks..

Disconnect connectors C140 and C144

Place mutimeter probes as follows,

Connector C140 place meter probe on the MALE Pin “E” and meter probe to chassis ground, (result should be open or NO continuity).

Connector C144 place meter probe on the FEMALE Pin “V” and meter probe to chassis ground, (result should be open or NO continuity).

Next

Connector C140 place meter probe on the MALE Pin “E”

Connector C144 place black probe on the FEMALE Pin “V”

You should have a resistance reading (as you are reading the solenoid). If you have no reading, then this circuit is OPEN and you will have to move down the circuit to find the fault (s).



If the above test shows and “open” circuit, you will need to verify the transmission wire harness> at the 20-Way Connector on the transmission with the meter, check for continuity on pins “E” and “U”.

Post up your results or fix.

Cheers,

Goose

 

I performed these test and got the results that were expected. I was also able to read the resistance reading coming from the solenoid.
any other ideas?


Thanks for your help!

 

If the system wiring checks out with the car static (parked), then I suspect you are dealing with a thermal/vibration issue with the solenoid and/or a thermal/vibration issue with the internal trans wiring harness open/short.
To get a fix, further troubleshooting is needed by way of replacing the solenoid and internal trans wiring harness.
Cheers,
Goose