The ECU controls the shift solenoids by sending an electric current through a coil of wire that is wrapped around the piston mechanism inside the solenoid. If the computer detects an unusually low voltage situation somewhere along the shift solenoid C control circuit, it will store a DTC P0979.
How severe is the code?
Diagnostic code P0979 is triggered when the ECU has trouble controlling shift solenoid C (also known as number three). Transmission problems related to this OBDII code may not be very serious at first. But they will continue to worsen and eventually render a transmission non-functional.
Symptoms
Symptoms of a P0979 include:
- Exceptionally hard shifts
- The transmission cannot shift into gear
Causes
- Low transmission fluid level
- Dirty fluid/filter
- Corroded/broken connectors and/or damaged wiring
- Malfunctioning shift solenoid
How to diagnose the code?
Diagnosing an OBDII P0979 code should begin with a check of the transmission fluid. If it is dirty or low, this OBD2 code will be triggered. Damaged wiring or broken/corroded connectors can also cause problems with a solenoid. If none of these issues are present, the shift solenoid C itself will need to be tested.
What repairs will fix P0979?
- Service the transmission
- Replace or repair damaged wiring/connectors
- Replace the shift solenoid