What Does P2799 Mean?
The transmission control module has detected a high voltage condition in the auxiliary transmission fluid pump control circuit. This pump is used to maintain transmission fluid pressure during engine-off or idle conditions, particularly in hybrid vehicles or vehicles with start-stop systems.
Common Causes
35%
Short to voltage in auxiliary pump wiring harness or connector pins
30%
Failed auxiliary transmission fluid pump motor or internal short
20%
Faulty transmission control module (TCM) output driver
15%
Damaged or corroded pump control circuit connector
Diagnostic Steps
1
Step 1: Disconnect the auxiliary transmission pump connector and check for voltage at the pump side with key on - should be 0V
2
Step 2: Inspect wiring harness from TCM to pump for chafing, pinching, or short to power
3
Step 3: Measure resistance of auxiliary pump motor (typically 1-5 ohms) and check for short to voltage
4
Step 4: Monitor pump control command from TCM using scan tool while checking actual voltage at pump connector
5
Step 5: If all wiring and pump test good, suspect TCM internal driver failure
Estimated Repair Cost
$150 - $1,200
Parts + labor, varies by vehicle and location
The transmission control module has detected a high voltage condition in the auxiliary transmission fluid pump control circuit. This pump is used to maintain transmission fluid pressure during engine-off or idle conditions, particularly in hybrid vehicles or vehicles with start-stop systems.
The most common cause of P2799 (Auxiliary Transmission Fluid Pump Control Circuit High) is: Short to voltage in auxiliary pump wiring harness or connector pins
Typical repair costs for P2799 range from $150 to $1,200, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Vehicle may experience reduced transmission cooling and lubrication during idle or stop-start operation. Extended driving may cause transmission overheating and damage.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P2799 to identify the root cause.
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Quick Info
Category
Powertrain
System
Transmission Fluid Management
Difficulty
Type
Generic (SAE)
Recommended Tools
OBD2 Scanner
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