4L80-E / 4L85-E Automatic Transmission

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 modulator (PCM) controls the TCC PWM solenoid valve by providing a ground path on CKT 418. The current flows through the TCC PWM solenoid valve coil according to the duty cycle (percentage of ON 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 in the TCC PWM solenoid valve circuit or the TCC PWM solenoid 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 Running the DTC
^ The system voltage is 8.0-18.0 volts.
^ The engine is running greater than 300 RPM for greater than 7 seconds.
^ No shift solenoid DTCs P0751, P0753, P0756, or P0758.

Conditions for Setting the DTC
All Conditions for Running the DTC are met, and either of the following conditions occur for 4.3 out of 5 seconds.
^ The PCM commands the TCC PWM solenoid valve to OFF (0 percent) and the voltage input remains low (zero volts).
^ The PCM commands the TCC PWM solenoid valve to ON (100 percent) and the voltage input remains high (B+).

Action Taken When the DTC Sets
^ The PCM illuminates the malfunction indicator lamp for California emission vehicles.
^ The PCM inhibits TCC engagement.
^ The PCM inhibits 4th gear.
^ The PCM freezes shift adapts from being updated.
^ The PCM stores DTC P1860 in PCM history.

Conditions for Clearing the MIL/DTC
^ For California emissions, the PCM turns OFF the MIL during the third consecutive trip in which the diagnostic test runs and passes.
^ A scan tool can clear the MIL/DTC.
^ For 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 Federal emissions, 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.
^ 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.
4. This step tests for voltage to the TCC PWM solenoid valve circuit at the 20-way connector.
6. This step tests the ability of the PCM and wiring to control the ground circuit.
8. This step tests the resistance of the TCC PWM solenoid valve and the internal wiring harness.