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4L80-E Automatic Transmission

FAULT DIAGNOSIS

The 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