Just picked up my first Corvette a couple days ago, it's a 98, higher milage (223k) but engine and trans were replaced with new at 213k. I'm getting a p1860 code for the TCC PMW solenoid, before I take it to a shop I plan on doing some electrical troubleshooting but figured I'd ask here for previous experiences. The code only seems to show up when I am just sitting parked or driving at lower speeds, I drove 110 miles on the highway running 70-85mph and the light never came on until I slowed down and stopped to turn onto my road. I can clear the code and it shifts just fine, but when the code comes back it does slip just a little, as soon as I clear the code it shifts perfectly. This is why I was thinking it's an electrical issue but wanted to ask people with more experience what they thought. I've done a lot of reading so far about checking grounds and the C140/144 connectors under the battery, that is where I'm going to start. I do have a couple other codes but not performance related stuff (c1233/1255 and I believe a 2057).

 

Another note, it seems to affect the 2-3 shift.

 

is ur b
tcs/abs lights ?? c1255 would trigger that/??

 

Abs and TCS lights are on, I figured the 1255/1233 would cause that issue, I posted those incase they may relate to the p1860 also. My biggest concern right now is figuring out this shift issue. Were you saying it's possibly the B solenoid?

 

Since you replaced the trans what torque converter was used?

 

I did not personally replace it, I've only had the car a couple of days. Engine and trans were put in about 15k miles ago and the trans was all stock replacement including converter from what I was told.

 

Update.... today against better judgment I took someone else's troubleshooting and just went for what they said the issue was, I knew I should have dug in more myself but to late now.

Anyways, I replaced the A and B shift solenoids, I was told it was the B solenoid, replaced the filter and new fluid while I was in there. As soon as I start the car the p1860 code comes right back, nothing changed. I did some more digging and found a post for a 99 that had a similar issue, I started running through the pins checking continuity. My problem there is that all of the labeling on my connectors by the battery are worn off so I'm not 100% I had the right connector but the pin and wire color matched what was said. C140 pin E female side was good to ground, male side I had some continuity about 1.2 kOhms, c144 pin V I had open to ground on male and female side. I believe my next step should be pulling the connection at the transmission to verify wiring is good and then checking resistance at the trans for the solenoid, but I need to see if someone can verify I did check the right connections. Goose, I need ya man!! Lol

This car is a rescue project for me, needs a lot of TLC, it's my first Corvette and I want this thing performing like it should. It still shifts into all gears, the code comes up when I come to a stop or when I first start it (still in park), and sometimes with the 2-3 shift it will slip a little but I can quickly clear the code and it shifts into 3rd just fine.

 

OK let get ya rolling!
This Tech Data is applicable to the 1998 Model Year Car....

DTC P1860 TCC PWM Solenoid Circuit Electrical

Circuit Description
The Torque Converter Clutch Pulse Width Modulation Solenoid Valve (TCC PWM Sol. 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 Sol. 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 Sol. Valve circuit or the TCC PWM Sol. Valve, then DTC P1860 sets. DTC P1860 is a type A DTC.

Conditions for Setting the DTC
• The system voltage is 8-16 volts.
• The engine speed is greater than 450 RPM for 5 seconds.
• Not in fuel cutoff.
• The PCM commands first gear
• The TCC duty cycle is less than 10% or greater than 90%.
• All of the above conditions are met for 5 seconds and either of the following fail conditions occurs for 5 seconds:
- The PCM commands the solenoid ON (90%) and the voltage input remains high (B+).
- The PCM commands the solenoid OFF (0%) and the voltage input remains low (0 volt).

Action Taken When the DTC Sets
• The PCM illuminates the Malfunction Indicator Lamp (MIL).
• The PCM inhibits TCC engagement.
• The PCM inhibits 4th gear if the transmission is in hot mode.
• The PCM freezes shift adapts from being updated.
• DTC P1860 stores in PCM history.

Diagnostic Aids
• Inspect the wiring at the PCM, the transmission connector and all other circuit connecting points for the following conditions:
- A bent terminal - A backed out terminal
- A damaged terminal
- Poor terminal tension
- A chafed wire
- A broken wire inside the insulation
- Moisture intrusion
- Corrosion
• When diagnosing for an intermittent short or open condition, massage/wiggle the wiring harness while watching the test equipment for a change.

The transmission electrical connector is an important part of the transmission operating system. Any interference with the electrical connection can cause the transmission to set Diagnostic Trouble Codes (DTCs) or affect proper operation. The following items can affect the electrical connection:
Remember the following points:
• Bent pins in the connector from rough handling during connection and disconnection
• Wires backing away from the pins or coming uncrimped (in either the internal or the external wiring harness)
• Dirt contamination entering the connector when disconnected
• Pins in the internal wiring connector backing out of the connector or pushed out of the connector during reconnection
• Excessive transmission fluid leaking into the connector, wicking up into the external wiring harness and degrading the wire insulation
• Moisture intrusion in the connector
• Low pin retention in the external connector from excessive connection and disconnection of the wiring connector assembly
• Pin corrosion from contamination
• Damaged connector assembly

• In order to remove the connector, squeeze the two tabs toward each other and pull straight up without pulling by the wires.
• Limit twisting or wiggling the connector during removal. Bent pins can occur.
• Do not pry the connector off with a screwdriver or other tool.
• Visually inspect the seals to ensure that they are not damaged during handling.
• In order to reinstall the external wiring connector, first orient the pins by lining up the arrows on each half of the connector.
Push the connector straight down into the transmission without twisting or angling the mating parts.
• The connector should click into place with a positive feel and/or noise.
• Whenever the transmission external wiring connector is disconnected from the internal harness and the engine is operating, DTCs will set.
Clear these DTCs after reconnecting the external connector.


Test Description
A) Are DTCs P0740, P0753, P0758 and P0785 also set? Please respond with findings?
B) Inspect the ENG IGN1 fuse> If the fuse is open, inspect circuit 339 (PNK), the solenoids and the A/T Wiring Harness Assembly for a short to ground. Repair the circuit, the solenoids and the harness if necessary. Post up findings?
C) Power Test
1. Turn the ignition OFF.
2. Disconnect the transmission 20-way connector (additional DTCs may set).
3. Install J 39775 Jumper Harness on the engine side of the 20-way connector.
4. With the engine OFF, turn the ignition switch to the RUN position.
5. Connect a lest lamp from J 39775 Jumper Harness cavity E to ground.
Result> Is the test lamp on? Post Up results/findings?
D) TCC PWM Sol. Valve Test
1. Disconnect the A/T Wiring Harness Assembly at the TCC PWM Sol. Valve.
2. Measure the resistance of the TCC PWM Sol. Valve.
Is the resistance within the specified range? 10- 15 ohms? Post Up results/findings?
E) Shorted TCC PWM Sol. Valve wiring Test
Measure the resistance between terminal E and ground, and between terminal U and ground.
Are both readings greater than the specified value? 250 K ohms? Post Up results/findings?
F) Shorted Trans Harness test
1. Disconnect the A/T Wiring Harness Assembly at the TCC PWM Sol. Valve.
2. Measure the resistance between each of the component terminals and ground.
Are both readings greater than the specified value? 250 K ohms? Post Up results/findings?


1998 Model Year

1998 Model Year

1998 Model Year

Post all of your testing results and/or findings?
Cheers,
Goose

 

Thank you sir! I'm hoping to get out there today after work to check this. As far as the adapter goes for checking the wiring back to the engine bay, can I just use my own jumper between pins E and U or is there something special about the adapter listed?

 

The jumper harness is used to have easy access and reduce the risk of damaging the the trans connector or the engine/car side connector for pin-outs of the wires and power checks. the four green probes (two male pins and two female pins) are used the probe the jumper harness plugs power/continuity when connected to either the trans connector or the engine/car side connector.



Cheers,
Goose

 

Finally got a chance to go through most of this, all wiring and fuses were good, I didn't have that Jumper adapter so checking the wiring at the trans was a pain, I basically checked resistance back to the engine side and everything was good there. I ordered a new TCC PWM solenoid earlier this week and decided to drop the pan today and look at everything in there. Pulled the solenoid and checked resistance, it's supposed to be 10-15 ohms and was reading 22.5..... think I found the issue. Swapped it out, started the car and no CEL, victory.... took it for a drive and now I get a p0758 when it tries to shift into third, not every time, but probably 50-70% of the time... I've already replaced the A and B shift solenoids and now the TCC PWM, I changed the filter and all of the fluid. I'm hoping that once the new fluid gets run through there it will clear up but I'm not holding my breath... maybe it's time for a 4L65 swap...

 

Not sure it's time to swap out the trans just yet.....OK, let get his P0758 Code sorted out.
The 1-2 and 2-3 shift solenoid valves (also called A and B solenoids) are identical devices that control the movement of the 1-2 and 2-3 shift valves (the 3-4 shift valve is not directly controlled by a shift solenoid). The solenoids are normally open exhaust valves that work in four combinations to shift the transmission into different gears. The PCM energizes each solenoid by grounding the solenoid through an internal quad driver. This sends current through the coil winding in the solenoid and moves the internal plunger out of the exhaust position. When ON, the solenoid redirects fluid to move a shift valve.

DTC P0758 2-3 Shift Solenoid Circuit Electrical for a 1998 Model Year Car.
Circuit Description
The 2-3 Shift Solenoid Valve (2-3 SS Valve) controls the fluid flow acting on the 2-3 shift valves. The 2-3 SS Valve is a normally-open exhaust valve that is used with the 1-2 Shift Solenoid Valve in order to allow four different shifting combinations. The solenoid attaches to the control valve body within the transmission. The 2-3 SS Valve receives ignition voltage through circuit 339. The Powertrain Control Module (PCM) controls the solenoid by providing the ground path on circuit 1223.
When the PCM detects a continuous open or short to ground in the 2-3 SS Valve circuit or the 2-3 SS Valve, then DTC P0758 sets. DTC P0758 is a type A DTC.

Conditions for Setting the DTC
• The system voltage is 8-16 volts.
• The engine speed is 450 RPM for 5 seconds.
• Not in fuel cutoff
• All of the above conditions are met for 5 seconds and either of the following fail conditions occurs for 5 seconds.
- The PCM commands the solenoid ON and the voltage input remains high (B+).
- The PCM commands the solenoid OFF and the voltage input remains low (0 volts).

Action Taken When the DTC Sets
• The PCM illuminates the Malfunction Indicator Lamp (MIL).
• The PCM commands third gear only.
• The PCM commands maximum line pressure.
• The PCM inhibits TCC engagement.
• The PCM freezes shift adapts from being updated.
• DTC P0758 stores in PCM history.

Conditions for Clearing the MIL/DTC
• The PCM turns OFF the MIL after three consecutive trips without a failure reported.
• A scan tool can clear the DTC from the PCM history. The PCM clears the DTC from the PCM history if the vehicle completes 40 warm-up cycles without a failure reported.
• The PCM cancels the DTC default actions when the fault no longer exists and the ignition is OFF long enough in order to power down the PCM.

Diagnostic Aids
• Inspect the wiring at the PCM, the transmission connector and all other circuit connecting points for the following conditions:
- A bent terminal - A backed out terminal - A damaged terminal
- Poor terminal tension - A chafed wire
- A broken wire inside the insulation
- Moisture intrusion - Corrosion
• When diagnosing for an intermittent short or open condition, massage/wiggle the wiring harness while watching the test equipment for a change.

Testing
This step tests for power to the 2-3 SS Valve from the ignition through the fuse.
1. Turn the ignition OFF.
2. Disconnect the transmission 20-way connector (additional DTCs will set).
3. Install the J 39775 Jumper Harness on the engine side of the 20-way connector.
4. With the engine OFF, turn the ignition switch to the RUN position.
5. Connect a test lamp from J 39775 Jumper Harness cavity E to ground.
Is the test light ON?
NOTE> you may have done this test already troubleshooting the original fault code.

This step measures the resistance of the Automatic Transmission Wiring Harness Assembly (A/T Wiring Harness Assembly) and the 2-3 SS Valve.
1. Turn the ignition OFF.
2. Install the J 39775 Jumper Harness on the transmission side of the 20-way connector.
3. With Digital Multimeter (DMM) and J 35616-A Connector Test Adapter Kit, measure the resistance between terminals B and E.
Is the resistance within the specified range of 19- 31 ohms?
Using Digital Multimeter (DMM), measure the resistance between terminals B and E and ground.
Are both readings greater than the specified value 250 K ohms?

2-3 SS Valve Test
1. Disconnect the A/T Wiring Harness Assembly from the 2-3 SS Valve.
2. Measure the resistance of the 2-3 SS Valve.
Is the resistance within the specified range of 19- 31 ohms?
1. Disconnect the A/T Wiring Harness Assembly from the 2-3 SS Valve.
2. Using Digital Multimeter (DMM), measure the resistance from the component's terminals to ground.
Are both readings greater than the specified value 250 K ohms?


1998 Model Year

1998 Model Year

As you have already replaced the A and B solenoids, you may have a faulty solenoid or a faulty transmission wire harness which can also be replaced...

For those interested, pic of the typical trans replacement parts below, research your specific car model year for replacement applicable part numbers.

replacemce trans service parts





Cheers,
Goose

 

I am still having trouble with my 99. I am still getting code P1860 and need it cleared in order to eliminate check engine light and pass smog test.

Any help would be appreciated.
Thanks!

 

Know anybody with HPtuner or a local speed shop should be able to tune it out

 

My p1860 code ended up being the TCC PWM solenoid, it wasn't to bad to swap out, took me about an hour start to finish. Drop the trans pan, pull the filter off, swap the solenoid and put it back together. Worst part for me was refilling the trans while the car is running with straight pipes....

 

Nice, how did u narrow it down to TCC pwn sol?