P0978 means Shift Solenoid C Control Circuit Range/Performance. The control circuit for shift solenoid C is working but its readings are outside the expected range. It is a generic OBD-II code, so the definition is the same on any make, but the most likely cause varies by engine; confirm with a scan tool and the service information for your vehicle before buying parts.
What P0978 means
Electronically controlled automatics are run by a transmission control module (TCM), a separate box or part of the engine computer. It reads speed sensors, the range sensor and fluid temperature to decide when to shift, and drives solenoids that apply clutches and the torque converter clutch. Many basic code readers only show the generic P0700; a scan tool that reads the transmission module shows the specific fault. Check fluid level and condition first, since low or burnt fluid causes many transmission codes.
P0978 symptoms
- Stuck in one gear or limp mode
- Harsh or missing shifts
- Check engine light
Common causes of P0978
- Solenoid resistance out of range
- Corroded connector
- Internal harness damage
How to diagnose P0978
- Check transmission fluid level and condition first
- Check solenoid resistance at the case connector
- Check the circuit for opens and shorts
- Inspect the internal harness
Can you drive with P0978?
Only as needed until repaired.
P0978 tips
Transmission solenoid circuits often fail at the case connector, where fluid can wick into the pins; check it before replacing solenoids.
Will P0978 clear itself?
If the fault stops, the computer turns off the check engine light by itself after several drive cycles without seeing it again, and the code stays in memory as history for a while. Clearing P0978 with a scan tool after a repair is fine, but if the cause is still there the code returns, sometimes within one drive. Disconnecting the battery also clears codes on most vehicles, but it erases learned fuel trims and idle settings as well.
Related codes
| Code | Meaning |
|---|---|
| P0979 | Shift Solenoid C Control Circuit Low |
| P0760 | Shift Solenoid C |
| P0700 | Transmission Control System Malfunction |
Guides that help
When it is more than a sensor
If the fault turns out to be internal (worn clutches, a failed converter or a damaged valve body), compare a rebuild with a replacement in transmission rebuild vs replacement and transmission replacement cost, identify your unit with what transmission do I have?, and browse our transmissions.
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