Transmission Friction Element Slip Detected (P079A)
The P079A code indicates that the transmission control module (TCM) 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 severe internal damage.
1. Symptoms You Will Notice
- Check Engine Light illuminated
- Delayed or harsh shifting
- Transmission slipping or revving without acceleration
- Burning smell from transmission fluid
2. Most Common Causes
- Low transmission fluid level or degraded fluid
- Worn or burnt clutch packs or bands
- Faulty transmission solenoid or valve body
- Internal hydraulic leaks or pump failure
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 to identify low pressure circuits.
Step 3: Inspect wiring and connectors to solenoids; test solenoid resistance and operation.
Step 4: If no external issues found, remove transmission pan to inspect for debris and worn clutches.
4. Frequently Asked Questions
Is it safe to drive with this code?▼
No, driving with a slipping transmission can cause severe internal damage and lead to complete failure. Have it inspected immediately.
How much does it cost to fix?▼
Diagnosis typically costs $50-$150. Repairs range from a simple fluid change ($100-$250) to a full rebuild ($1,500-$3,500) depending on damage.
5. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.