DTC P1860 TCC PWM Solenoid Circuit Electrical. GMC Truck Savana 1997

Turn the ignition OFF.
Disconnect the transmission 20-way connector (additional DTCs may set).
Install the J 39775 Jumper Harness on the engine harness connector.
With the engine off, turn the ignition to the RUN position.
Connect a test lamp from the J 39775 Jumper Harness cavity E to ground.

Is the test lamp ON?

Go to Step 6

Go to Step 5

Repair the open or high resistance located in ignition voltage feed circuit 1020 to the TCC PWM Sol. Valve.

Refer to Electrical Diagnosis, Section 8.

Is the repair complete?

Install the test lamp between cavities E and S of the J 39775 Jumper Harness.
Use the scan tool in order to command the TCC PWM Sol. Valve ON and OFF three times.

Does the test lamp turn ON when you command the TCC PWM Sol. Valve ON, and does the lamp turn OFF when you command the TCC PWM Sol. Valve OFF?

Go to Step 8

Go to Step 7

Inspect circuit 418 for an open or short to ground.
Repair the circuit if necessary.

Refer to Electrical Diagnosis, Section 8.

Did you find a problem?

Go to Step 9

Install the J 39775 Jumper Harness on the transmission 20-way connector (Automatic Transmission Connector End View ).
Measure the resistance between terminals E and S. Use the J 39200 DMM and the J 35616 Connector Test Adapter Kit.

Is the resistance within the specified values?

10-15ohms

Go to Step 11

Go to Step 10

Replace the PCM.

Refer to Powertrain Control Module Replacement/Programming , Section 6.

Is the replacement complete?

Disconnect the internal wiring harness at the TCC PWM Sol. Valve.
Measure the resistance of the TCC PWM Sol. Valve.

Is the resistance within the specified values?

10-15ohms

Go to Step 12

Measure the resistance between terminal E and ground.
Measure the resistance between terminal S and ground.

Are both readings greater than the specified value?

250kohms

Go to Diagnostic Aids

Go to Step 13

Inspect the internal wiring harness for an open circuit.

Refer to Electrical Diagnosis, Section 8.

Did you find a problem?

Disconnect the internal wiring harness at the TCC PWM Sol. Valve.
Measure the resistance between each of the component terminals and ground.

Are both readings greater than the specified value?

250kohms

Go to Step 14

Inspect the internal wiring harness for a short to ground.

Refer to Electrical Diagnosis, Section 8.

Did you find a problem?

Replace the TCC PWM Sol. Valve.

Refer to Control Valve Body Removal and Disassembly, in On-Vehicle Service.

Is the replacement complete?

Replace the Automatic Transmission Wiring Harness Assembly (A/T Wiring Harness Assy).

Refer to Interior Wiring Harness Replacement, in On-Vehicle Service.

Is the replacement complete?

Begin the diagnosis again. Go to Step 1

In order to verify your repair, perform the following procedure:

Select DTC.
Select Clear Info.
Operate the vehicle under the following conditions:

•	The TCC PWM Sol. Valve is commanded ON and the volts drop to zero.

•	The TCC PWM Sol. Valve is commanded OFF and the volts increase to B+.

•	All conditions are met for 5 seconds.

Select Specific DTC. Enter DTC P1860.

Has the test run and passed?

System OK

DTC P1860 TCC PWM Solenoid Circuit Electrical Gas

Automatic Transmission Components Gas Engines
Automatic Transmission Controls Schematics Gas Engines
OBD II Symbol Description Notice
Handling ESD Sensitive Parts Notice

Circuit Description

The Torque Converter Clutch Width Modulation Solenoid Valve (TCC PWM Solenoid Valve) controls fluid acting on the converter clutch valve, which then controls TCC apply and release. The TCC PWM Sol. Valve attaches to the control valve body within the transmission. Ignition voltage goes directly to the TCC PWM Sol. Valve. The Vehicle Control Modulator (VCM) controls the TCC PWM Sol. Valve by providing a ground path on circuit 418. The current flows through the TCC PWM Sol. Valve coil according to the duty cycle (percentage of ON time). The TCC PWM Sol. Valve provides a smooth engagement of the torque converter clutch by operating on a duty cycle percent of ON time.

If the VCM detects a continuous open or short in the TCC PWM Sol. Valve circuit or the TCC PWM Sol. Valve, then DTC P1860 sets. DTC P1860 is a type D DTC. For California emission vehicles DTC P1860 is a type A DTC.

Conditions for Setting the DTC

•	The system voltage is 10-16.5 volts.

•	The engine is running and not in fuel cutoff.

•	No shift solenoid DTCs P0751, P0753, P0756, or P0758.

•	All of the above conditions are met and one of the following conditions are met for 5 seconds.

-	The VCM commands the TCC PWM Sol. Valve to OFF (0%) and the voltage remains low (zero volts).

-	The VCM commands the TCC PWM Sol. Valve to ON (100%) and the voltage remains high (B+).

Action Taken When the DTC Sets

•	The VCM inhibits TCC engagement.

•	The VCM inhibits 4th gear.

•	The VCM freezes shift adapts from being updated.

•	The VCM illuminates the Malfunction Indicator Lamp.

Conditions for Clearing the DTC

For California emissions vehicles, the VCM turns OFF the MIL after three consecutive ignition cycles without a failure reported.
A scan tool can clear the DTC from the VCM history. The VCM clears the DTC from the VCM history if the vehicle completes 40 warm-up cycles without a failure reported.
The VCM cancels the DTC default actions when the fault no longer exists and the ignition is OFF long enough in order to power down the VCM.

Diagnostic Aids

•	Inspect the wiring for poor electrical connections at the VCM. Inspect the wiring for poor electrical connections at the transmission 20-way connector. Look for the following problems:

-	A bent terminal

-	A backed out terminal

-	A damaged terminal

-	Poor terminal tension

-	A chafed wire

-	A broken wire inside the insulation

•	When diagnosing for an intermittent short or open, massage the wiring harness while watching the test equipment for a change.

•	First diagnose and clear any engine DTCs or TP Sensor codes that are present. Then inspect for any transmission DTCs that may have reset.

Test Description

The numbers below refer to the step numbers on the diagnostic table.

This step tests for voltage to the TCC PWM Sol. Valve circuit at the 20-way connector.

This step tests the ability of the VCM and wiring to control the ground circuit.

This step tests the resistance of the TCC PWM Sol. Valve and the internal wiring harness.

P1860

Step

Action

Value(s)

Yes

Was the Powertrain On-Board Diagnostic (OBD) System Check performed?

Go to Step 2

Go to:

Powertrain On Board Diagnostic (OBD) System Check (4.3L)

Powertrain On Board Diagnostic (OBD) System Check (5.7L and 7.4L)

Install the Scan Tool ®.
With the engine OFF, turn the ignition switch to the RUN position.

Important: Before clearing the DTCs, use the scan tool in order to record the Freeze Frame and Failure Records for reference. The Clear Info function will erase the data.

Record the DTC Freeze Frame and Failure Records.
If DTCs P0753, P0758, or P1860 are set, inspect the fuse.

Is the fuse open?

Go to Step 3

Go to Step 4

Inspect the following components for a short to ground.

•	Circuit 1020

•	The TCC PWM Sol. Valve

•	The Automatic Transmission Wiring Harness Assembly

Refer to Electrical Diagnosis, Section 8.

Did you find and correct a problem?

Turn the ignition OFF.
Disconnect the transmission 20-way connector (additional DTCs may set).
Install the J 39775 Jumper Harness on the engine harness connector.
With the engine off, turn the ignition to the RUN position.
Connect a test lamp from the J 39775 Jumper Harness cavity E to ground.

Is the test lamp ON?

Go to Step 6

Go to Step 5

Repair the open or high resistance in ignition voltage feed circuit 1020 to the TCC PWM Sol. Valve.

Refer to Electrical Diagnosis, Section 8.

Is the repair complete?

Install the test lamp from cavities E to S of the J 39775 Jumper Harness.
Command the TCC PWM Sol. Valve ON and OFF three times.

Does the test lamp turn ON when you command the TCC PWM Sol. Valve ON, and does the lamp turn OFF when you command the TCC PWM Sol. Valve OFF?

Go to Step 8

Go to Step 7

Inspect circuit 418 for an open or short to ground.
Repair the circuit if necessary.

Refer to Electrical Diagnosis, Section 8.

Did you find a problem?

Go to Step 9

Install the J 39775 Jumper Harness on the transmission 20-way connector (Automatic Transmission Connector End View).
Using the J 39200 DMM and the J 35616 Connector Test Adapter Kit, measure the resistance between terminals E and S.

Is the resistance within the specified values?

10-15ohms

Go to Step 11

Go to Step 10

Replace the VCM.

Refer to VCM Replacement/Programming (With KS Calibration PROM) , Section 6.

Is the replacement complete?

Disconnect the Automatic Transmission Wiring Harness Assembly at the TCC PWM Sol. Valve.
Measure the resistance of the TCC PWM Sol. Valve.

Is the resistance within the specified values?

10-15ohms

Go to Step 12

Measure the resistance between terminal E and ground.
Measure the resistance between terminal S and ground.

Are both readings greater than the specified value?

250kohms

Go to Diagnostic Aids

Go to Step 13

Inspect the internal wiring harness for an open circuit.

Refer to Electrical Diagnosis, Section 8.

Did you find a problem?

Disconnect the Automatic Transmission Wiring Harness Assembly at the TCC PWM Sol. Valve.
Measure the resistance between each of the component terminals and ground.

Are both readings greater than the specified value?

250kohms

Go to Step 14

Inspect the Automatic Transmission Wiring Harness Assembly for a short to ground.

Refer to Electrical Diagnosis, Section 8.

Did you find a problem?

Replace the TCC PWM Sol. Valve.

Refer to Control Valve Body Removal and Disassembly, in On-Vehicle Service.

Is the replacement Complete?