Transmission Friction Element Slip Detected
The P079F code indicates that the transmission control module (TCM) has detected unexpected slip in one or more friction elements (clutches or bands) inside the automatic transmission. This slip is measured by comparing input and output shaft speed sensors; when the difference exceeds a calibrated threshold, the code sets. Common causes include low transmission fluid, worn clutches, valve body issues, or faulty solenoids. If left unaddressed, this can lead to severe transmission damage.
01. Most Common Causes
- Low or contaminated transmission fluid
- Worn or burnt friction plates
- Faulty shift solenoid or valve body
- Internal transmission leaks or pump failure
02. Symptoms You Will Notice
- Delayed or harsh shifting
- Transmission slipping during acceleration
- Check Engine Light illuminated
- Overheating transmission
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 TCM and solenoids.
Step 4: If fluid and electrical checks pass, internal disassembly may be needed to inspect clutches and bands.
04. Commonly Affected Makes
05. Frequently Asked Questions
Is it safe to drive with this code?▼
No, continued driving can cause severe internal damage. Have the vehicle towed to a shop.
How much does it cost to fix?▼
Diagnosis is $50-$150. Repairs range from a simple fluid change ($100-$200) to a full rebuild ($1,500-$3,500).