4L80-E / 4L85-E Automatic Transmission

DTC P1860 (Diesel)












Circuit Description with 4L80-E / 4L85-E Automatic Transmission
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. 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 8-18 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 (0 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 records the operating conditions when the Conditions for Setting the DTC are met. The PCM stores this information as Freeze Frame and Failure Records.
^ 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 can clear the MIL/DTC.
^ For Federal and California emissions, the PCM clears the DTC from PCM history if the vehicle completes 40 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 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
^ An open in the ignition feed circuit 1020, causes multiple DTCs to set.
^ A short to voltage on the TCC PWM solenoid ground circuit can set P0741 and P1870.
^ DTC P1860 defaults to an elevated line pressure condition which may result in TCC partial apply. This may induce idle surge and engine stall.

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.
6. This step tests the ability of the PCM and wiring to control the TCC PWM solenoid valve ground circuit.
8. This step tests the resistance of the TCC PWM solenoid valve and the automatic transmission wiring harness assembly.
12. If the automatic transmission wiring harness assembly is open, do not repair the wiring harness. You must replace the automatic transmission wiring harness assembly.