What Does P079C Mean?
The TCM has detected slippage in transmission friction element C. The speed sensor data shows that element C is not holding or driving its gear set properly, allowing rotational slip. This can manifest as flared shifts, loss of power, or inability to maintain speed in the gears controlled by element C.
Safety Warning
Friction element slippage causes unreliable power delivery. The vehicle may lose drive power unexpectedly, which is dangerous in traffic. Drive only at low speeds to a repair facility. Do not tow or carry heavy loads.
Common Causes
35%
Worn friction element C clutch pack (friction material worn below threshold)
25%
Insufficient transmission fluid level or severely degraded fluid
15%
Apply piston or seal leak in element C circuit
15%
Hydraulic pressure loss in element C apply circuit from valve body issue
10%
Overheated clutch material (glazed) from prolonged slip condition
Diagnostic Steps
1
Identify gears using friction element C from the transmission clutch apply chart and test for slip in those specific gears.
2
Monitor RPM flare during shifts involving element C — compare commanded vs actual gear ratios.
3
Check and correct transmission fluid level and condition before further diagnosis.
4
Perform line pressure testing in the gears where element C is applied.
5
Inspect the transmission cooler and cooler lines for restrictions that could cause overheating and fluid breakdown.
6
If pressure is adequate and fluid is good, internal friction element wear requires transmission removal and rebuild.
Estimated Repair Cost
$300 - $3,500
Parts + labor, varies by vehicle and location
The TCM has detected slippage in transmission friction element C. The speed sensor data shows that element C is not holding or driving its gear set properly, allowing rotational slip. This can manifest as flared shifts, loss of power, or inability to maintain speed in the gears controlled by element...
The most common cause of P079C (Transmission Friction Element "C" Slip Detected) is: Worn friction element C clutch pack (friction material worn below threshold)
Typical repair costs for P079C range from $300 to $3,500, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Friction element slippage causes unreliable power delivery. The vehicle may lose drive power unexpectedly, which is dangerous in traffic. Drive only at low speeds to a repair facility. Do not tow or carry heavy loads.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P079C 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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