Transmission Friction Element Slip Detected
Code P079E indicates that the transmission control module (TCM) has detected unexpected slip in one or more friction elements (clutches or bands) within the automatic transmission. 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
- Delayed or harsh gear engagement
- Transmission slipping during acceleration
- Check Engine Light illuminated
- Overheating transmission
2. Most Common Causes
- Excessive wear of the friction pack for element E
- Hydraulic pressure leak in the element E circuit
- Faulty or stuck pressure control solenoid valve
- Damaged O-ring or accumulator piston seal
- Improper transmission fluid level or condition (low, contaminated, wrong type)
- Internal mechanical issues with the oil pump or valve body
- Faulty transmission input or output speed sensor
- TCM software update required
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 solenoids; test solenoid resistance.
Step 4: Perform a stall test or road test to confirm slip pattern.
4. Frequently Asked Questions
Is it safe to drive with this code?▼
No, continued driving can cause severe internal damage and complete transmission 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 solenoid replacement ($300-$800) or 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.