Shift Timing Solenoid B Range/Performance
The P078B code indicates that the Powertrain Control Module (PCM) has detected a malfunction in the shift timing solenoid B circuit. This solenoid controls hydraulic pressure to engage specific gears in the automatic transmission. The 'range/performance' aspect means the solenoid's response time or electrical characteristics are outside expected parameters, often due to internal wear, electrical faults, or transmission fluid issues.
01. Most Common Causes
- Faulty shift timing solenoid B
- Low or contaminated transmission fluid
- Wiring or connector issues in solenoid circuit
- Internal transmission mechanical failure
02. Symptoms You Will Notice
- Harsh or delayed gear shifts
- Transmission slipping
- Check Engine Light illuminated
- Reduced fuel economy
03. Step-by-Step Diagnosis
Step 1: Scan for codes and record freeze frame data.
Step 2: Check transmission fluid level and condition.
Step 3: Inspect wiring and connectors for damage or corrosion.
Step 4: Test solenoid resistance and operation with a multimeter.
Step 5: Perform a transmission pressure test if needed.
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 it can cause further transmission damage. Short trips to a repair shop may be acceptable if shifting is still possible.
How much does it cost to fix?▼
Repair costs typically range from $150 to $400, including parts and labor. Solenoid replacement is common, but additional repairs may increase cost.