What Does P079A Mean?
The TCM has detected slippage in transmission friction element A. Friction elements (clutch packs, bands, or brake assemblies) are responsible for holding or driving specific gear sets. When slip is detected, it means the friction element is not fully engaging, allowing the input and output sides to rotate at different speeds. This indicates wear, insufficient clamping pressure, or fluid issues.
Safety Warning
Transmission slippage can cause sudden loss of drive power or RPM flares during acceleration. This is a safety concern during highway merging or passing. Limit driving to low-speed, low-load conditions. Continued driving will cause rapid deterioration of the friction material and can lead to complete transmission failure.
Common Causes
35%
Worn friction element A clutch pack (friction material degraded)
25%
Low or contaminated transmission fluid reducing clamping pressure
15%
Faulty apply servo or piston for friction element A
15%
Pressure control solenoid not delivering adequate apply pressure
10%
Valve body cross-leak reducing apply pressure to element A
Diagnostic Steps
1
Identify which gear(s) friction element A is active in by consulting the transmission clutch apply chart for your specific transmission model.
2
Monitor input shaft speed vs output shaft speed in the affected gear(s) — a difference confirms actual slippage.
3
Check transmission fluid level and condition — low level or burnt fluid is the most common cause of slip.
4
Perform a line pressure test in the affected gear to verify adequate apply pressure reaches the friction element.
5
If pressure is low, diagnose the pressure control solenoid and valve body circuits feeding element A.
6
If pressure is adequate but slip persists, the friction element itself is worn and internal transmission repair is required.
Estimated Repair Cost
$300 - $3,500
Parts + labor, varies by vehicle and location
The TCM has detected slippage in transmission friction element A. Friction elements (clutch packs, bands, or brake assemblies) are responsible for holding or driving specific gear sets. When slip is detected, it means the friction element is not fully engaging, allowing the input and output sides to...
The most common cause of P079A (Transmission Friction Element "A" Slip Detected) is: Worn friction element A clutch pack (friction material degraded)
Typical repair costs for P079A range from $300 to $3,500, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Transmission slippage can cause sudden loss of drive power or RPM flares during acceleration. This is a safety concern during highway merging or passing. Limit driving to low-speed, low-load conditions. Continued driving will cause rapid deterioration of the friction material and can lead to complete transmission failure.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P079A to identify the root cause.
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Quick Info
Category
Powertrain
System
Automatic Transmission
Difficulty
Type
Generic (SAE)
Recommended Tools
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