Shift Solenoid Control Circuit Range/Performance
The P0978 code indicates that the Powertrain Control Module (PCM) has detected a performance or range issue in the shift solenoid control circuit. This solenoid is responsible for regulating hydraulic pressure to engage specific gears in the automatic transmission. The fault may be due to electrical problems (open, short, or high resistance), mechanical sticking of the solenoid, or low transmission fluid level. This can lead to harsh or delayed shifts, transmission slipping, or limp mode.
01. Most Common Causes
- Faulty shift solenoid
- Wiring or connector damage in the solenoid circuit
- Low or contaminated transmission fluid
- Internal transmission mechanical failure
02. Symptoms You Will Notice
- Check Engine Light illuminated
- Harsh or delayed gear shifts
- Transmission slipping or stuck in gear
- Reduced fuel economy
03. Step-by-Step Diagnosis
Step 1: Scan for codes and record freeze frame data.
Step 2: Inspect transmission fluid level and condition; top off or replace if necessary.
Step 3: Visually check wiring and connectors for damage, corrosion, or loose connections.
Step 4: Test solenoid resistance and power/ground circuits with a multimeter.
Step 5: Perform a solenoid actuation test using a scan tool to verify operation.
04. Commonly Affected Makes
05. Frequently Asked Questions
Is it safe to drive with this code?▼
It is not recommended to drive long distances as the transmission may shift erratically or fail, potentially causing a safety hazard.
How much does it cost to fix?▼
Repair costs typically range from $150 to $400, including parts and labor, depending on whether the solenoid or wiring needs replacement.