4L80-E / 4L85-E Automatic Transmission

Diagnostic Chart:

Schematic:

Circuit Description with 4L80-E / 4L85-E Automatic Transmission
The 1-2 Shift Solenoid (SS) valve controls the fluid flow action on the 1-2 and the 3-4 shift valves. The 1-2 88 valve is a normally-open exhaust valve that is used with the 2-3 shift solenoid (SS) valve to allow tour different shifting combinations.

When the Powertrain Control Module (PCM) detects a 2-2-3-3 gear ratio, then DTC P0751 sets. DTC P0751 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 088 DTCs P0722 or P0723.
^ No ISS DTCs P0716 or P0717.
^ No TFP manual valve position switch DTCs P1810, P1815, P1816, P1817 or P1818.
^ No shift solenoid electrical DTCs P1842, P1843, P1845 or P1847.
^ TFT is 20-130°C (68-266°F).
^ The APP angle is greater than 10%.
^ The vehicle speed is greater than 3.2 km/h (2 mph).
^ The engine torque is 108-644 N.m (80-475 lb ft).
^ The engine speed is below 3,750 RPM.
^ Not in Four Wheel Drive Low.
^ No Four Wheel Drive DTC P1875.
^ No TCC PWM solenoid valve DTC 1860.
^ No MAP DTCs P0106, P0107 and P0108.

CONDITIONS FOR SETTING THE DTC

Stuck Off (for two occurrences)
^ First gear is commanded with a ratio equal to second gear for greater than 1.5 seconds.
^ Fourth gear is commanded, with TCC applied or locked, with a ratio equal to third gear for greater than 3.5 seconds.

Stuck On (for five occurrences)
Second gear is commanded and the gear ratio equals first gear for greater than 2.2 seconds.

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 P0751 in the 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
^ Verify that the transmission meets the specifications in the Shift Speed table.
^ Other internal transmission failures may cause similar shift patterns.
^ First, diagnose and clear any engine DTCs or APP sensor codes that are present. Then inspect for any transmission DTCs that may have reset.
^ Refer to Shift Solenoid Valve State and Gear Ratio table.

TEST DESCRIPTION
The numbers below refer to the step numbers on the diagnostic table.
2. This step tests the function of the TFP manual valve position switch.
3. This step tests whether the scan tool commanded all the shifts, or whether all the shift solenoids responded correctly, but all the shifts did not occur.