DTC P1860 TCC PWM Solenoid Circuit Electrical. GMC Truck Savana 1999

Go to Diagnostic Aids

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 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 (PNK) to the TCC PWM solenoid valve.

Refer to Wiring Repairs in Wiring Systems.

Is the repair complete?

Install the test lamp from cavities E to S of the J 39775 .
Command the TCC PWM solenoid valve ON and OFF three times.

Does the test lamp turn ON when you command the TCC PWM solenoid valve ON, and does the lamp turn OFF when you command the TCC PWM solenoid valve OFF?

Go to Step 8

Go to Step 7

Inspect circuit 418 (BRN) for an open or short to ground.

Refer to General Electrical Diagnosis in Wiring Systems.

Repair the circuit if necessary.

Refer to Wiring Repairs in Wiring Systems.

Was the condition found?

Go to Step 9

Install the J 39775 on the transmission 20-way connector (Automatic Transmission Connector End View).
Using the J 39200 digital multimeter (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 (4.3L) or VCM Replacement/Programming (5.7L) or VCM Replacement/Programming (7.4L) in Engine Controls.

Is the replacement complete?

Disconnect the automatic transmission wiring harness assembly at the TCC PWM solenoid valve.
Measure the resistance of the TCC PWM solenoid 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 A/T wiring harness assembly for an open circuit.

Refer to General Electrical Diagnosis in Wiring Systems.

Was the condition found?

Disconnect the automatic transmission wiring harness assembly at the TCC PWM solenoid 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 General Electrical Diagnosis in Wiring Systems.

Was the condition found?

Replace the TCC PWM solenoid valve.

Refer to Control Valve Body Removal and Disassembly.

Is the replacement complete?

Replace the automatic transmission wiring harness assembly.

Refer to Internal Wiring Harness Replacement.

Is the replacement complete?

Perform the following procedure in order to verify the repair:

Select DTC.
Select Clear Info.
Select the parameters, TCC Duty Cycle, TCC duty Cycle Open/Shorted to Ground and TCC Duty Cycle Shorted to Voltage.
Operate the vehicle under the following conditions:

•	The TCC PWM Solenoid Valve is commanded ON and TCC Duty Cycle Shorted to Voltage is NO.

•	The TCC PWM Solenoid Valve is commanded OFF and TCC Duty Cycle Open/Shorted to Ground is NO.

•	Each condition is met for 5 seconds.

Select Specific DTC.
Enter DTC P1860.

Has the test run and passed?

System OK

Go to Step 1

DTC P1860 TCC PWM Solenoid Circuit Electrical Diesel

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

Circuit Description

The torque converter clutch pulse width modulation (TCC PWM) solenoid valve controls fluid acting on the converter clutch valve, which then controls TCC apply and release. The TCC PWM solenoid valve attaches to the control valve body within the transmission. Ignition voltage goes directly to the TCC PWM solenoid valve. The powertrain control module (PCM) controls the TCC PWM solenoid valve by providing a ground path on circuit 418. The current flows through the TCC PWM solenoid valve 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 on a duty cycle percent of ON time.

If 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. DTC P1860 is a type A DTC.

Conditions for Running the DTC

•	System voltage is 8.0-18.0 volts.

•	The engine is running more than 475 RPM for greater than 7 seconds.

•	Commanded gear is 1st.

Conditions for Setting the DTC

All of the above conditions are met, and either of the following conditions occur for 4.3 seconds out of 5 seconds.

•	The PCM commands the solenoid OFF, and the voltage input remains low (zero volts).

•	The PCM commands the solenoid to ON (100%) and the voltage input remains high (B+).

Action Taken When the DTC Sets

•	The PCM illuminates the malfunction indicator lamp (MIL).

•	The PCM inhibits TCC engagement.

•	The PCM inhibits 4th gear.

•	The PCM stores DTC P1860 in PCM history.

Conditions for Clearing the MIL/DTC

•	For Federal and California emissions, the PCM turns OFF the MIL during the third consecutive trip in which the diagnostic test runs and passes.

•	A scan tool clears the DTC from PCM history.

•	For Federal and California emissions, the PCM clears the DTC from PCM history if the vehicle completes 40 consecutive warm-up cycles without an emission related diagnostic fault occurring.

•	For vehicles equal to or greater than 15,000 lbs GVW, the PCM clears the DTC from PCM history if the vehicle completes 40 consecutive warm-up cycles without a non-emission related diagnostic fault occurring.

•	The PCM cancels the DTC default actions when the fault no longer exists and the ignition switch 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 backed out terminal

-	A damaged terminal

-	Reduced terminal tension

-	A chafed wire

-	A broken wire inside the insulation

-	Moisture intrusion

Corrosion

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

•	An open in the ignition feed circuit 1020, causes multiple DTCs to set.

•	First, diagnose and clear any present engine DTCs. 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 solenoid valve.

This step tests the ability of the PCM and wiring to control the TCC PWM solenoid valve ground circuit.

This step tests the resistance of the TCC PWM solenoid valve and the automatic transmission wiring harness assembly.

If the automatic transmission wiring harness assembly is open, do not repair the wiring harness. You must replace the automatic transmission wiring harness assembly.

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

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

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

Is the fuse open?

Go to Step 3

Go to Step 4

Inspect circuit 1020 (PNK), the three solenoids and the automatic transmission wiring harness assembly for a short to ground.

Refer to General Electrical Diagnosis in Wiring Systems.

Was the shorted condition corrected?

Go to Diagnostic Aids

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

Is the test lamp ON?

Go to Step 6

Go to Step 5

Repair the open or high resistance in ignition feed circuit 1020 (PNK) to the TCC PWM solenoid valve.

Refer to Wiring Repairs in Wiring Systems.

Is the repair complete?

Install the test lamp from cavity E to cavity S of the J 39775 .
Use the scan tool output control function in order to command the TCC PWM solenoid valve ON and OFF three times.

Does the test lamp illuminate when you command the TCC PWM solenoid valve ON, and does the lamp turn OFF when you command the TCC PWM solenoid valve OFF?

Go to Step 8

Go to Step 7

Inspect circuit 418 (BRN) for an open or short to ground.

Refer to General Electrical Diagnosis in Wring Systems.

Repair the circuit if necessary.

Refer to Wiring Repairs in Wiring Systems.

Was an open or short to ground condition found?

Go to Step 9

Install the J 39775 on the transmission side of the 20-way connector.
Measure the resistance between terminals E and S. Use the J 39200 digital multimeter (DMM) and the J 35616 connector test adapter kit.

Is the resistance within the specified value?

10-15ohms

Go to Step 11

Go to Step 10

Replace the PCM.

Refer to Powertrain Control Module Replacement/Programming in Engine Controls.

Is the replacement complete?

Disconnect the automatic transmission wiring harness assembly at the TCC PWM solenoid valve.
Measure the resistance of the TCC PWM solenoid valve.

Is the resistance within the specified value?

10-15ohms

Go to Step 12

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

Are both readings greater than the specified value?

250kohms

Go to Diagnostic Aids

Go to Step 13

Inspect the automatic transmission wiring harness assembly for an open circuit.

Refer to General Electrical Diagnosis in Wring Systems.

Was an open condition found?

Disconnect the automatic transmission wiring harness assembly at the TCC PWM solenoid valve.
Measure the resistance between each of the component terminals and a good 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 General Electrical Diagnosis in Wring Systems.

Was a short to ground condition found?

Replace the TCC PWM solenoid valve.

Refer to Control Valve Body Replacement.

Is the replacement complete?

Replace the automatic transmission (A/T) wiring harness assembly.

Refer to Automatic Transmission Wiring Harness Replacement.

Is the replacement complete?