4L80-E / 4L85-E Automatic Transmission
DTC P0977
Circuit Description
The 2-3 shift solenoid (SS) valve controls the fluid flow acting on the 2-3 shift valves. The solenoid is a normally-open exhaust valve. With the 1-2 SS valve, the 2-3 SS valve allows 4 different shifting combinations. The solenoid attaches to the control valve body within the transmission. The 2-3 SS valve receives voltage through the ignition voltage circuit. The transmission control module (TCM) controls the solenoid by providing the ground path on the 2-3 SS valve control circuit.
When the TCM detects a continuous short to voltage in the 2-3 SS valve control circuit, then DTC P0977 sets. DTC P0977 is a type A DTC.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P0977 2-3 Shift Solenoid (SS) Control Circuit High Voltage
Conditions for Running the DTC
^ The system voltage is 8-18 volts.
^ The engine is running for 5 seconds or greater.
Conditions for Setting the DTC
The TCM detects a short to voltage in the 2-3 SS valve circuit for 4.4 seconds.
Action Taken When the DTC Sets
^ The TCM requests the engine control module (ECM) to illuminate the malfunction indicator lamp (MIL).
^ The TCM commands maximum line pressure.
^ The TCM inhibits 4th gear.
^ The TCM freezes transmission adaptive functions.
^ The ECM records the operating conditions when the Conditions for Setting the DTC are met. The ECM stores this information as Freeze Frame and Failure Records.
^ The TCM records the operating conditions when the Conditions for Setting the DTC are met. The TCM stores this information as Failure Records.
^ The TCM stores DTC P0977 in TCM history during the second consecutive trip in which the Conditions for Setting the DTC are met.
Conditions for Clearing the DTC
^ The ECM turns OFF the MIL after the third consecutive drive trip in which the TCM does not send a MIL illumination request.
^ A scan tool can clear the DTC.
^ The TCM clears the DTC from TCM history if the vehicle completes 40 warm-up cycles without an emission related diagnostic fault occurring.
^ The TCM cancels the default actions when the ignition is OFF long enough in order to power down the TCM.
