Transmission Friction Element Slip Detected (P079D)
The P079D code indicates that the transmission control module (TCM) has detected unexpected slip in a friction element (such as a clutch or band) during operation. This typically means the component is worn, damaged, or not receiving proper hydraulic pressure, leading to inefficient power transfer and potential transmission damage.
01. Most Common Causes
- Low transmission fluid level or dirty fluid
- Worn or burnt friction plates/clutches
- Faulty transmission valve body or solenoid
- Internal hydraulic pressure issues
02. Symptoms You Will Notice
- Transmission slipping or delayed engagement
- Harsh or erratic shifting
- Check Engine Light illuminated
- Reduced fuel economy
03. Step-by-Step Diagnosis
Step 1: Check transmission fluid level and condition; top off or replace if necessary.
Step 2: Scan for additional codes and perform a transmission pressure test.
Step 3: Inspect wiring and connectors to the transmission solenoids and TCM.
Step 4: If no external issues found, internal inspection of friction elements may be required.
04. Commonly Affected Makes
05. Frequently Asked Questions
Is it safe to drive with this code?▼
No, driving with a slipping transmission can cause further damage and lead to complete transmission failure. It's best to have it diagnosed and repaired promptly.
How much does it cost to fix?▼
Cost varies widely: a simple fluid change may cost $50-$150, while replacing friction elements or a valve body can range from $500 to $2,500 or more.