Each shift solenoid is responsible for controlling different clutches and gears. If a particular shift solenoid does not operate as it has been programmed to, a DTC P0978 will be recorded.
How severe is the code?
Although the severity of a diagnostic code P0978 may not seem too bad at first, transmission problems will worsen, eventually leading to a transmission that will not shift gears.
Symptoms
Symptoms of a P0978 include:
- Harsh shifts
- The transmission cannot shift into gear
Causes
- Low transmission fluid
- Dirty fluid/filter
- Damaged wiring and/or corroded or broken connectors
- Malfunctioning shift solenoid
How to diagnose the code?
Transmission fluid is very important for the operation of a shift solenoid. Believe it or not, dirty or low transmission fluid can actually trigger an OBDII fault code P0978, which should be the first thing to check. Damaged wiring or broken connectors along the transmission wiring harness can also cause this OBD2 code. If no issues are detected in either of these areas, the C shift solenoid should be checked.
What repairs will fix P0978?
- Service the transmission
- Replace or repair damaged wiring/connectors
- Replace the shift solenoid