4L80-E / 4L85-E Automatic Transmission

Diagnostic Chart:

Schematic:

Circuit Description with 4L80-E / 4L85-E Automatic Transmission
The Powertrain Control Module (PCM) energizes the Torque Converter Clutch Pulse Width Modulated (TCC PWM) solenoid valve by grounding circuit 418. This blocks the exhaust for TCC signal fluid and allows filtered 2-3 drive fluid to feed the TCC signal circuit. When the vehicle's operating conditions are appropriate for TCC application, the PCM begins the TCC duty cycle to approximately 30%. This allows TCC signal fluid pressure to move the converter clutch shift valve into the apply position and direct regulated apply fluid to the torque converter. The PCM then increases (ramps) the duty cycle to approximately 60%, where regulated apply fluid pressure, applies the converter clutch. The vehicle application determines the TCC apply rate. Once the TCC applies, the duty cycle immediately increases to approximately 70% to achieve full apply pressure, in the regulated apply fluid circuit.

The TCC PWM solenoid valve is de-energized by the PCM opening circuit 418. This action allows the TCC signal fluid to exhaust through the solenoid and blocks filtered 2-3 drive fluid from entering the TCC signal circuit. The loss of fluid pressure in the TCC signal circuit releases the TCC.

If the PCM detects low TCC slip when the TCC is commanded OFF, then DTC P0742 sets. DTC P0742 is a type B DTC.

CONDITIONS FOR RUNNING THE DTC
^ The system voltage is 8.0-18.0 volts.
^ The engine speed is greater than 475 RPM for greater than 7 seconds.
^ No OSS DTCs P0502 or P0503.
^ No ISS DTCs P0716 or P0717.
^ No TFP manual valve position switch DTCs P1810, P1815, P1816, P1817 or P1818.
^ No TCC PWM electrical DTC P1860.
^ No TCC Stuck OFF DTC P0741.
^ No MAP DTCs.
^ TCC duty cycle is 0%.
^ Commanded gear is not 1st.
^ TFP manual valve position switch indicates D4.
^ TFT is 20-130°C (68-266°F).
^ The APP angle is greater than 15%.
^ The engine torque is 176-644 N.m (130-475 lb ft).
^ Engine speed is less than 3,200.

CONDITIONS FOR SETTING THE DTC
^ TCC slip is greater than -10.0 RPM, but less than 10.0 RPM.
^ All conditions for running the DTC are met for 3.0 seconds for 4 occurrences.

ACTION TAKEN WHEN THE DTC SETS
^ The PCM illuminates the Malfunction Indicator Lamp (MIL).
^ The PCM commands maximum line pressure.
^ The PCM freezes shift adapts.
^ The PCM stores DTC P0742 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
^ If the TCC is mechanically stuck ON, with the parking brake applied and any gear range selected, the TCC fluid mechanically applies the TCC. TCC fluid mechanically applying the TCC can cause an engine stall.
^ A stuck or skewed APP sensor may set DTC P0742.
^ First, diagnose and clear any engine DTCs 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.
3. This step tests the mechanical state of the TCC. When the PCM commands the TCC solenoid OFF, the slip speed should increase.