Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
DTC Advanced Diagnostics: P0979
DTC P0979 : Shift Solenoid Valve C Circuit Low
General Description
Shift solenoid valve C opens/closes the drain circuit by the transmission control module (TCM) ON/OFF commands. The switching of the fluid passages to supply/discharge the hydraulic pressure of the lock-up shift valve which controls the torque converter clutch, is done by the shift solenoid valve C ON/OFF control. The TCM commands the driver circuit to turn ON shift solenoid valve C. The driver circuit equips diagnosis function to detect and output open circuit and short circuit of shift solenoid C and returns a return signal against the TCM command. When the return signal does not match to the TCM command to turn ON shift solenoid valve C, the TCM detects a malfunction and stores a DTC.
Monitor Execution, Sequence, Duration, DTC Type
| Execution | Continuous |
| Sequence | None |
| Duration | 1.0 second or more |
| DTC Type | One drive cycle, MIL on, shift position indicator blinks |
Enable Conditions
| Condition | Minimum | Maximum |
|---|---|---|
| 12 volt battery voltage [Battery Voltage] | 11.0 V | - |
[ ]: HDS Parameter
Malfunction Threshold
The return signal does not match to the command to turn ON shift solenoid valve C for at least 1.0 second.
Possible Cause
The causes shown may not be a complete list of all potential problems, and it is possible that there may be other causes.
- Solenoid wire harness failure
- Valve body assembly failure (shift solenoid valve C)
- TCM internal circuit failure
Confirmation Procedure
Operating Condition
- Start the engine.
- While pressing the brake pedal, shift the transmission to N position/mode.
Diagnosis Details
Conditions for setting the DTC
When a malfunction is detected, the MIL comes on, the shift position indicator blinks, and a Pending DTC, a Confirmed DTC, and the freeze data are stored in the TCM memory.
Conditions for clearing the DTC
The shift position indicator comes off by turning the vehicle to the OFF (LOCK) mode. The MIL is cleared if the malfunction does not return in three consecutive trips in which the diagnostic runs. The MIL, the Pending DTC, the Confirmed DTC, and the freeze data can be cleared with the scan tool clear command.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.
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