What Does P079D Mean?
The TCM has detected slippage in transmission friction element D. This internal clutch or band assembly is failing to fully engage when commanded, causing rotational speed differences across the element. The driver may notice RPM flaring, soft or slipping shifts, or reduced power transfer in specific gears where element D is responsible for gear holding or driving.
Safety Warning
Unpredictable power delivery and potential loss of drive in affected gears. Avoid highway driving and heavy loads. Drive only at low speeds if necessary and schedule immediate repair. Continued operation will cause accelerated internal damage.
Common Causes
35%
Worn friction element D clutch discs or band lining
25%
Low or contaminated transmission fluid
15%
Hydraulic apply circuit leak (servo piston, seals, or checkball)
15%
Valve body issue reducing apply pressure to element D
10%
Band anchor or strut failure (if element D is a band)
Diagnostic Steps
1
Consult the clutch/band apply chart to determine which gears friction element D controls.
2
Test for slip in those gears by monitoring input vs output shaft speed ratios during steady driving and shifts.
3
Verify transmission fluid level and condition — address any deficiency before further diagnosis.
4
Perform line pressure testing in the affected gear(s) to determine if hydraulic pressure is adequate.
5
If equipped with a band, check band adjustment (if adjustable) or band condition.
6
If hydraulic pressure is correct but slip continues, internal rebuild to replace worn friction material is necessary.
Estimated Repair Cost
$300 - $3,500
Parts + labor, varies by vehicle and location
The TCM has detected slippage in transmission friction element D. This internal clutch or band assembly is failing to fully engage when commanded, causing rotational speed differences across the element. The driver may notice RPM flaring, soft or slipping shifts, or reduced power transfer in specifi...
The most common cause of P079D (Transmission Friction Element "D" Slip Detected) is: Worn friction element D clutch discs or band lining
Typical repair costs for P079D range from $300 to $3,500, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Unpredictable power delivery and potential loss of drive in affected gears. Avoid highway driving and heavy loads. Drive only at low speeds if necessary and schedule immediate repair. Continued operation will cause accelerated internal damage.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P079D to identify the root cause.
OBDHut Mobile App
Scan codes directly from your car with the OBDHut app.
Coming Soon
Quick Info
Category
Powertrain
System
Automatic Transmission
Difficulty
Type
Generic (SAE)
Recommended Tools
OBD2 Scanner
A quality scan tool helps you read codes, view live data, and clear faults.
