4L80-E / 4L85-E Automatic Transmission

Diagnostic Chart (Part 1 Of 3):

Diagnostic Chart (Part 2 Of 3):

Diagnostic Chart (Part 3 Of 3):

Schematic:

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 Vehicle Control Modulator (VCM) controls the TCC PWM solenoid valve by providing a ground path. 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 VCM 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 C DTC. For California emission vehicles DTC P1860 is a type A DTC.

CONDITIONS FOR RUNNING THE DTC
^ The engine is running greater than 475 RPM for 7 seconds.
^ No shift solenoid DTCs P0751, P0753, P0756, or P0758.
^ No system voltage DTC P0560.
^ Commanded gear is first.

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 VCM commands the TCC PWM solenoid valve to OFF (0%) and the voltage input remains low (zero volts).
^ The VCM commands the TCC PWM solenoid valve to ON (100%) and the voltage input remains high (B+).

ACTION TAKEN WHEN THE DTC SETS
^ The VCM illuminates the malfunction indicator lamp for California emission vehicles.
^ The VCM inhibits TCC engagement.
^ The VCM inhibits 4th gear.
^ The VCM freezes shift adapts from being updated.
^ The VCM records the operating conditions when the Conditions for Setting the DTC are met. The VCM stores this information as Freeze Frame (Calif. only) and Failure Records (Calif. and Federal).
^ The VCM stores DTC P1860 in VCM history.

CONDITIONS FOR CLEARING THE MIL/DTC
^ For California emissions, the VCM 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 VCM clears the DTC from VCM history if the vehicle completes 40 consecutive warm-up cycles without an emission related diagnostic fault occurring.
^ For Federal emissions, the VCM clears the DTC from VCM history if the vehicle completes 40 consecutive warm-up cycles without a non-emission related diagnostic fault occurring.
^ The VCM cancels the DTC default actions when the fault no longer exists and/or the ignition switch is OFF long enough in order to power down the VCM.

DIAGNOSTIC AIDS
^ First diagnose and clear any engine DTCs or TP sensor codes that are present. Then inspect for any transmission DTCs that may have reset.
^ Inspect the connectors at the VCM, the AT wiring harness and all other circuit connecting points for an intermittent condition. Refer to Testing for Intermittent and Poor Connections in Diagrams.
^ Inspect the circuit wiring for an intermittent condition. Refer to Testing for Electrical Intermittents in Diagrams.

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 VCM and wiring to control the ground circuit.
8. This step tests the resistance of the TCC PWM solenoid valve and the internal wiring harness.