Transmission Friction Element Slip Detected
Code P079B indicates that the transmission control module (TCM) has detected unexpected slip in a friction element (such as a clutch or band) during operation. This slip can be caused by low transmission fluid, worn friction plates, a faulty solenoid, or internal hydraulic issues. The TCM monitors input and output shaft speeds to determine if the gear ratio is correct; if the ratio deviates beyond a threshold, this code sets. Continued driving may lead to further transmission damage.
1. Symptoms You Will Notice
- Check Engine Light illuminated
- Harsh or delayed shifting
- Transmission slipping during acceleration
- Reduced fuel economy
2. Most Common Causes
- Low or contaminated transmission fluid
- Worn or burnt friction plates
- Faulty shift solenoid or pressure control solenoid
- Internal transmission hydraulic failure
3. Step-by-Step Diagnosis
Step 1: Scan for additional codes and check freeze frame data.
Step 2: Inspect transmission fluid level and condition; top off or replace if necessary.
Step 3: Perform a transmission pressure test to identify hydraulic issues.
Step 4: Test solenoids and wiring for proper resistance and operation.
4. Frequently Asked Questions
Is it safe to drive with this code?▼
It is not recommended. Driving with a slipping transmission can cause further damage and lead to complete transmission failure.
How much does it cost to fix?▼
Diagnosis typically costs $50-$150. Repairs can range from a simple fluid change ($100-$200) to solenoid replacement ($200-$500) or a full transmission rebuild ($1500-$4000).
5. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.