What Does P0978 Mean?
The TCM has detected that Shift Solenoid C (SS-C) is not performing within its expected operating range. SS-C typically controls hydraulic routing for third and fourth gear engagement or overdrive in many transmission designs. The solenoid is electrically connected but its mechanical output does not match what the TCM commands, resulting in shift quality problems on the affected gear transitions.
Common Causes
35%
Shift Solenoid C sticking or responding sluggishly due to contamination or wear
25%
Degraded or contaminated transmission fluid impeding solenoid function
20%
Worn valve body passages or check balls associated with SS-C
15%
Elevated wiring resistance in the SS-C circuit slowing solenoid response
5%
TCM adaptive values for SS-C operation out of calibration
Diagnostic Steps
1
Check transmission fluid level and condition — contaminated fluid is the primary contributor to shift solenoid performance issues.
2
Using the scan tool, identify which specific gear transitions are affected and correlate them with SS-C operation. Monitor commanded vs. actual gear ratios.
3
Measure SS-C resistance at the transmission connector to verify it is within manufacturer specification. Also check total circuit resistance for any added resistance.
4
Service the transmission fluid and filter, reset TCM adaptive values, and perform a comprehensive road test across multiple drive cycles to evaluate shift quality.
5
If fluid service does not improve performance, remove the valve body to physically inspect SS-C and its bore for contamination, wear, or damage.
Estimated Repair Cost
$200 - $1,200
Parts + labor, varies by vehicle and location
The TCM has detected that Shift Solenoid C (SS-C) is not performing within its expected operating range. SS-C typically controls hydraulic routing for third and fourth gear engagement or overdrive in many transmission designs. The solenoid is electrically connected but its mechanical output does not...
The most common cause of P0978 (Shift Solenoid "C" Control Circuit Range/Performance) is: Shift Solenoid C sticking or responding sluggishly due to contamination or wear
Typical repair costs for P0978 range from $200 to $1,200, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Shift quality issues on specific gear transitions can be disconcerting but are not immediately hazardous. Prolonged operation with a malfunctioning shift solenoid risks clutch pack damage and transmission overheating. Address before the condition worsens.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P0978 to identify the root cause.
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Quick Info
Category
Powertrain
System
Automatic Transmission / Transaxle
Difficulty
Type
Generic (SAE)
Recommended Tools
OBD2 Scanner
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