Transmission Friction Element Slip Detected (P079D)
The P079D code indicates that the powertrain control module (PCM) has detected unexpected slip in one of the transmission's friction elements, such as a clutch or band. This slip occurs when the actual gear ratio differs from the commanded ratio, often due to worn friction material, low fluid pressure, or hydraulic circuit issues. Prolonged slip can cause overheating and internal damage.
1. Symptoms You Will Notice
- Hesitation or delayed engagement when shifting
- Transmission slipping or flaring between gears
- Check Engine Light illuminated
- Unusual noises (whining, buzzing) from transmission
2. Most Common Causes
- Low transmission fluid level or dirty fluid
- Worn or burnt friction plates/bands
- Faulty transmission control solenoid
- Internal hydraulic pressure leak
3. 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 transmission solenoids for damage.
Step 4: If fluid and electrical checks pass, remove transmission pan to inspect for debris and worn friction material.
4. Frequently Asked Questions
Is it safe to drive with this code?▼
No, driving with P079D can cause further transmission damage and lead to complete failure. Have it diagnosed and repaired promptly.
How much does it cost to fix?▼
Diagnosis typically costs $50-$150. Repairs range from a simple fluid change ($100-$250) to solenoid replacement ($200-$500) or a full rebuild ($1,500-$4,000).
5. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.