4L80-E Automatic Transmission
FAULT DIAGNOSISThe following checks are intended as a guide to diagnosis of possible mechanical faults in the 4L80-E hydraulic transmission unit; electrical faults are covered in the Electrical Diagnostic Manual. When the fault involves a leak, it is recommended that it is located by the use of a crack detection fluid, eg Met-L-Check, which is available in spray form and permits the leak to be located after a short test drive.
Initial Checks
Note: Before attempting diagnosis, ensure that the following settings are checked:
Transmission oil level
Note: This oil level can only be checked correctly when the transmission is at normal operating temperature
^ Ensure that the transmission is at normal operating temperature of 90°C by conducting a 15 to 20 mile road test. If starting from cold, check for presence of oil on dipstick at idle in Park to the 'Cold' reference mark before start of road test.
^ Check that the vehicle is on level ground.
^ Select 'P' Park.
^ Firmly apply the parking and foot brakes and run the engine at idle speed.
^ To ensure that the system is primed. slowly move the selector lever through all the gear positions.
^ With the engine still running, engage 'P' Park, withdraw the dipstick and wipe with a lint free cloth.
^ Replace the dipstick slowly and withdraw it noting the level.
^ Top up as required and recheck the level.
Engine Tune
Kick-down switch adjustment.
Stall Test
^ Ensure the transmission is at normal running temperature.
^ Fully apply the parking brake.
^ Start the engine.
^ Fully depress the footbrake.
^ Select position 'D'- Drive.
^ Fully depress the accelerator('kick-down' detent fully depressed).
^ Note the tachometer reading.
^ Compare the tachometer reading to the specification.
CAUTION: This test must not last more than 5 seconds. Always allow the engine to idle for at least 2 minutes between tests to allow the transmission fluid to cool down. Do not carry out more than three tests in any half-hour.
Road Test
^ Fully check all shift speeds and note. Compare the results with the specification in addition to general observations of transmission behaviour, noises, leaks etc., and consult the following Fault Finding Chart.
CAUTION: When renewing the transmission, ALWAYS flush out the oil cooler and feed and return pipes.
Electrical Checks
^ If any electrical component fault is suspected, refer to Electrical Diagnostic Manual (EDM) to verify the failure mode before a repair or replacement is attempted.
Transmission Fault Codes
Fault Finding is carried out by the use of the portable diagnostic unit (PDU). All types of fault, whether mechanical or electrical, cause transmission fault codes to be displayed on the PDU. Refer to the Electrical Diagnostic Manual (EDM) for electrical faults.
P1608 Watchdog Fault
P0702 Transmission Control System Electrical
P0705 Transmission Range Sensor Circuit Malfunction
P0706 Transmission Range Sensor Circuit Range / Performance
P0715 Input/Turbine Speed Sensor Circuit Malfunction
P0716 Input/Turbine Speed Sensor Circuit Range / Performance
P0720 Output Speed Sensor Circuit Malfunction
P0721 Output Speed Sensor Circuit Range/Performance
P0722 Output Speed Sensor Circuit No Signal
P0726 Engine Speed Input Circuit Range / Performance
P0727 Engine Speed Input Circuit No Signal
P1739 Transmission Component Slipping
P0742 Torque Converter Clutch System Stuck On
P7043 Torque Converter Clutch System Electrical
P0751 Shift Solenoid 'A' Performance
P0753 Shift Solenoid 'A' Electrical
P0756 Shift Solenoid 'B' Performance
P0758 Shift Solenoid 'B' Electrical
P1775 Transmission System Check Engine Lamp Fault
P1776 Ignition Retard Request Duration Fault
P1780 Torque Reduction Signal Malfunction
P1781 Torque Signal Malfunction Range / Performance
P1786 Mode Switch Input Malfunction
P1790 Throttle Position Signal System Range / Performance
P1791 Throttle Position Electrical Failure
P1794 System Voltage Malfunction