Each shift solenoid is responsible for controlling different clutches and gears. If a particular shift solenoid is not performing the way it has been programmed to do, then a P0978 DTC will be saved.
How Serious is the Code?
Although the severity of a P0978 diagnostic trouble code may not seem too bad at first, the transmission problems will get a lot worse. Eventually leading to a transmission that will not shift into different gears.
Symptoms of a P0978 include:
- Harsh shifts
- Transmission may not shift into gear
- Low transmission fluid
- Dirty transmission fluid/filter
- Damaged wiring and/or corroded or broken connectors
- Shift solenoid malfunction
How to Diagnose the Code?
Transmission fluid is very important to the operation of a shift solenoid. Believe it or not, dirty or low transmission fluid can actually cause a P0978 OBDII trouble code, so that should be the first thing that is checked. Damaged wiring or broken connectors along the transmission wiring harness can also cause this OBD2 code. If no issues are found in either of these areas, then the shift solenoid C should be checked.
What Repairs Will Fix P0978?
- Service the transmission
- Replace or repair damage wiring/connectors
- Replace shift solenoid
- P0979 – Shift Solenoid “C” Control Circuit Low
- P0980 – Shift Solenoid “C” Control Circuit High