P0977

DTC P0977

Circuit Description
The shift solenoid 1 and the shift solenoid 2 operate together in order to electronically control the shifting of the transmission from 1st gear to 4th gear (overdrive). The Powertrain Control Module (PCM) outputs the system voltage in order to perform the following actions:
^ Turn on (energize) either solenoid.
^ Turn off (de-energize) either solenoid.
The PCM performs the above actions when necessary.

The transmission shifts with the combination of both solenoids turning on and off. The shift solenoid 1 is normally ON in the 1st and the 2nd gears. The shift solenoid 1 does not operate in the 3rd and the 4th gears. The shift solenoid 2 is normally ON in the 2nd and the 3rd gears. The shift solenoid 2 does not operate in the 1st and the 4th gears. The 4th gear (overdrive) is obtained when both of the shift solenoids are not operating.

The scan tool can be used to turn the shift solenoids on or off to verify proper operation. Monitoring the operation of the solenoids can also be done using the scan tool during a road test.

Conditions for Setting the DTC
The voltage detected at PCM terminal 1 is 5.5 volts or higher when the PCM commands the shift solenoid 2 OFF.

Action Taken When the DTC Sets
^ DTC P0977 stores.
^ The PCM enters the fail-safe mode.
^ The Malfunction Indicator Lamp (MIL) turns on.

During the fail-safe mode operation, 3rd gear operates instead of the 1st and the 2nd gears when the manual selector is in DRIVE range. The torque converter clutch does not engage.

Diagnostic Aids
Inspect for the following conditions:
^ An open shift solenoid 2
^ Open electrical circuits between the shift solenoid 2 and the PCM
^ A faulty PCM

The following conditions may cause an intermittent:
^ A reduced connection
^ A broken wire inside the insulation

Inspect the PCM harness connectors for the following conditions:
^ Backed out terminals
^ Improper mating
^ Broken locks
^ Improperly formed or damaged terminals
^ Reduced terminal-to-wire connections

If DTC P0977 cannot be duplicated, the information included in the Scan Tool Freeze Frame data may be useful in determining the vehicle operating conditions when the DTC set.

DTC Confirmation Procedure
1. Turn the ignition switch to the LOCK position.
2. Connect the scan tool to the Data Link Connector (DLC).
3. Turn the ignition switch ON.
4. Use the scan tool in order to clear the following items:
^ DTC P0977
^ Any pending DTCs
5. Start the engine.
6. Apply the brake pedal firmly
7. Shift the manual selector to DRIVE range. Remain in DRIVE range for 10 seconds.
8. Release the brake, then accelerate the vehicle in DRIVE range. Continue driving for 10 seconds at 30 km/h (20 mph). Increase vehicle speed to 80 km/h (50 mph) for 10 seconds.
9. Stop the vehicle.
10. Use the scan tool in order to test for a pending DTC.

Test Description
The numbers below refer to the step numbers on the diagnostic table.
1. The Powertrain OBD System Check prompts the technician to complete some basic checks and store the freeze frame data on the scan tool if applicable. The scan tool creates an electronic copy of the data taken when the fault occurred. The information then stores in the scan tool for later reference.
3. This step tests the shift solenoid 2 circuit for a short to voltage.
4. This step tests the shift solenoid internal coil resistance.
5. This step tests shift solenoid 2 circuit for an open.
6. This step inspects the condition of the transmission internal electrical harness for damage.
7. This step tests for a reduced electrical connection that may have set DTC P0977.
8. This step tests for a faulty PCM.

Steps 1 - 10:

Steps 11 - 14:

DTC P0977