4L80-E / 4L85-E Automatic Transmission

Diagnostic Chart (Part 1 Of 3):

Diagnostic Chart (Part 2 Of 3):

Diagnostic Chart (Part 3 Of 3):

Schematic:

CIRCUIT DESCRIPTION
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 SS valve is a normally-open exhaust valve that is used with the 2-3 SS valve to allow for four different shifting combinations. The 1-2 SS valve attaches to the control valve body within the transmission. The ignition voltage goes directly to the 1-2 SS valve. The VCM controls the 1-2 SS Valve by providing the ground path through circuit 1222.

When the Vehicle Control Module (VCM) detects a continuous open or short in the 1-2 SS valve circuit or the 1-2 SS valve, then DTC P0753 sets. DTC P0753 is a type C DTC. For California emissions vehicles, DTC P0753 is a type A DTC.

CONDITIONS FOR RUNNING THE DTC
The system voltage is 10-16 volts.
^ The ignition is ON.
^ The engine runs more than 475 RPM for greater than 7 seconds.

CONDITIONS FOR SETTING THE DTC
All conditions for running the DTC are met, and either of the following conditions occur for 4.3 out of 5 seconds.
^ The VCM commands the solenoid on, and the voltage input remains high (B+).
^ The VCM commands the solenoid off and the voltage input remains low.

ACTION TAKEN WHEN THE DTC SETS
^ The VCM illuminates the Malfunction Indicator Lamp (MIL) for California emissions vehicles.
^ The VCM commands maximum line pressure.
^ The VCM freezes shift adapts.
^ The VCM inhibits 3-2 downshifts above 25 MPH.
^ The VCM records the operating conditions when the Conditions for Setting the DTC are met. The VCM stores this information as Freeze Frame and Failure Records.
^ The VCM stores DTC P0753 in VCM history.

CONDITIONS FOR CLEARING THE MIL/DTC
^ For California emissions, the VCM 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 California emissions, the VCM clears the DTC from VCM history if the vehicle completes 40 consecutive warm-up cycles without an emission related diagnostic fault occurring.
^ For Federal emissions, the VCM clears the DTC from VCM history if the vehicle completes 40 consecutive warm-up cycles without a non-emission related diagnostic fault occurring.
^ The VCM cancels the DTC default actions when the fault no longer exists and/or the ignition switch is OFF long enough in order to power down the VCM.

DIAGNOSTIC AIDS
^ First diagnose and clear any engine DTCs or TP sensor codes that are present. Then inspect for any transmission DTCs that may have reset.
^ An open ignition feed on circuit 1020 can cause multiple DTCs to set.
^ Refer to Shift Solenoid Valve State and Gear Ratio table.
^ Inspect the connectors at the VCM, the AT wiring harness and all other circuit connecting points for an intermittent condition. Refer to Testing for Intermittent and Poor Connections in Diagrams.
^ Inspect the circuit wiring for an intermittent condition. Refer to Testing for Electrical Intermittents in Diagrams.

TEST DESCRIPTION
The numbers below refer to the step numbers on the diagnostic table.
4. This step tests the function of the 1-2 SS valve and the internal wiring harness.
5. This step tests the power to the 1-2 SS valve from the ignition through the fuse.
7. This step tests the ability of the VCM and the wiring to control the ground circuit.
10. This step measures the resistance of the automatic transmission wiring harness assembly and the 1-2 SS valve.