P2799 code meaning
Electric/Auxiliary Transmission Fluid Pump A Control Circuit High
Powertrain system Generic code P27xx codes Check engine light
What P2799 means
P2799 is set when the control line of auxiliary pump A sits at too high a level, normally because it touches a powered wire. GM's 2025 TCM tables are the only public manufacturer description: the module measures under 0.5 Ω from the signal line to a voltage source in 20 of 25 samples spaced 100 ms apart, provided supply voltage is between 9 and 15 V, and treats the result as Type B with the MIL after two trips. The tables also show that the pump may be fed by one of several high-side drivers, and the check only runs while the relevant driver is on. CARB requires such actuator circuits to be monitored for shorts. Look for chafed harness sections near hot or moving parts and pins bridged by moisture. With the pump unusable, stop-start and pressure support at restart are lost.
P2799 at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modePossible
- Repair difficultyMedium
- Typical labor0.5 to 3 hours
- Clears after repairWhen cleared with a scanner
Symptoms of P2799
- MIL after two drive cycles
- Stop-start inoperative
- Rough engagement after an auto-start
Common causes of P2799
- Most likelyControl wire shorted to a powered circuit
- PossibleMoisture bridging pins in the pump connector
- PossibleInternal short in the pump electronics
- Less likelyFaulty high-side driver in the module
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Aux trans pump aWiring harness
What each part of P2799 means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 2 | Generic code (second SAE range): it means the same on every make. |
| 7 | Area: transmission. |
| 99 | The exact fault in that area. |
What to do next
- Note P2799 and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about P2799
What does P2799 mean?
P2799 means "Electric/Auxiliary Transmission Fluid Pump A Control Circuit High". P2799 is set when the control line of auxiliary pump A sits at too high a level, normally because it touches a powered wire. It is a generic code, so it means the same on every make.
Is it safe to drive with P2799?
Drive gently and only to a workshop. With P2799 the car can go into limp mode (reduced power) to protect itself.
Will P2799 fail an emissions test?
Yes, it can. P2799 is emissions-related, so most inspection programs fail a car while it is stored or while the check engine light is on.
How hard is P2799 to fix?
Difficulty: medium. A typical repair takes 0.5 to 3 hours of work. This is a job for a workshop.
Will P2799 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.