P0979

DTC P0979

Circuit Description
The shift solenoid (SS) valve 3 is a normally open valve that mounts into the transmission case. The SS valve 3 controls the modulator pressure to the shift valve 3, as commanded by the powertrain control module (PCM). When the PCM energizes the SS valve 3, it closes the passage to the shift valve 3, and the modulator pressure is exhausted. When the PCM de-energizes the SS valve 3, it allows the modulator pressure to apply to the shift valve 3. The PCM has a diagnosis circuit inside, to monitor the voltage level to the SS valve 3, and receives a return signal. When the PCM detects a short to ground on the SS valve 3 high control circuit, DTC P0979 sets. DTC P0979 is a type A DTC.


Conditions for Running the DTC
- No Clutch PC Solenoid Valve 1 DTCs P0746 or P0747.
- No SS Valve Performance DTC P0751.
- No Clutch PC Solenoid Valve 2 DTC P0777.
- No Clutch PC Solenoid Valve 1 DTCs P0962 or P0963.
- No Clutch PC Solenoid Valve 2 DTCs P0966 or P0967.
- No SS Valve 1 DTCs P0973 or P0974.
- No SS Valve 2 DTCs P0976 or P0977.
- No SS Valve 3 DTC P0980.
- No TCC PC Solenoid DTCs P2763 or P2764.
- No TCC Enable Solenoid DTCs P2769 or P2770.
- System voltage is greater than 11 volts.
- The engine is running.
- The vehicle is in D range for 1 second or greater.

Conditions for Setting the DTC
The PCM detects a short to ground on the SS valve 3 high control circuit for 1 second or greater.

Action Taken When the DTC Sets
- The PCM illuminates the malfunction indicator lamp (MIL).
- The PCM limits the transmission shift to 4th gear.
- The PCM records the operating conditions when the Conditions for Setting the DTC are met. The PCM stores this information as Freeze Frame and Failure Records.
- The PCM stores DTC P0979 in PCM history.

Conditions for Clearing the MIL/DTC
- The PCM 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.
- The PCM clears the DTC from PCM history if the vehicle completes 40 warm-up cycles without an emission related diagnostic fault occurring.

Diagnostic Aids
- Inspect the connectors at the PCM, the SS valve 3, and all other circuit connecting points for an intermittent condition.
- Inspect the circuit wiring for an intermittent condition.
- Inspect for a shorted SS valve 3 circuit.
- Inspect for a faulty SS valve 3.
- Inspect for a PCM internal fault.

Test Description
The numbers below refer to the step numbers on the diagnostic table.
2. During the shift solenoid valve 3 operation, listen for an audible click. Command the ON and the OFF states. Repeat the commands as necessary.
3. This step verifies that the PCM is providing voltage to the shift solenoid valve 3.
4. This step tests for an open in the ground circuit to the shift solenoid valve 3.

Steps 1 - 7:

Steps 8 - 12:

DTC P0979