Transmission Friction Element Slip Detected
Code P079C indicates that the transmission control module (TCM) has detected unexpected slip in a friction element (clutch or band) during operation. This means the component is not holding properly, causing a difference between input and output shaft speeds. Common causes include low or contaminated transmission fluid, worn friction plates, a faulty solenoid, or internal hydraulic issues. If left unaddressed, it can lead to severe transmission damage.
01. Most Common Causes
- Low or dirty transmission fluid
- Worn or burnt friction plates
- Faulty shift solenoid
- Internal transmission hydraulic failure
02. Symptoms You Will Notice
- Check Engine Light illuminated
- Delayed or harsh shifting
- Transmission slipping during acceleration
- Overheating transmission
03. Step-by-Step Diagnosis
Step 1: Scan for codes and check freeze frame data.
Step 2: Inspect transmission fluid level and condition; top off or replace if needed.
Step 3: Perform a transmission pressure test to identify hydraulic issues.
Step 4: Test shift solenoids and wiring for proper operation.
Step 5: If no external issues found, internal inspection may be required.
04. Commonly Affected Makes
05. Frequently Asked Questions
Is it safe to drive with this code?▼
No, driving with P079C can cause further damage to the transmission. It is best to have it diagnosed and repaired promptly.
How much does it cost to fix?▼
Cost varies: a fluid change may cost $50-$150, solenoid replacement $200-$500, and a full rebuild $1500-$3500.