P2799
Electric/Auxiliary Transmission Fluid Pump A Control Circuit High
Transmission controls
Generic OBD-II
Medium
What it means
P2799 means the transmission controller detects an abnormally high (open or shorted-to-voltage) signal in the auxiliary transmission fluid pump control circuit. This electric pump keeps line pressure up when the engine idle-stops, so the usual effect is disabled auto start-stop and delayed engagement on restart — not a no-start. The cause is typically wiring, the connector, or the pump itself.
Medium
Can I keep driving? Usually yes — the main pump still runs while the engine is on; you mainly lose the auxiliary pump's help during auto start-stop, with a risk of delayed engagement.
Common symptoms
What you'll notice
- Check-engine light on
- Auto start-stop disabled or restarts feel delayed
- Brief delay or bump when the transmission re-engages after an auto restart
- Possible transmission overheating under heavy use
Common causes
Most likely first
- Open or short-to-voltage in the auxiliary pump control circuitLikely
- Faulty auxiliary transmission fluid pump or its driver/relayCommon
- Corroded or loose pump connectorCommon
- Chafed wiring between the TCM and pumpLess often
- Transmission control module output fault (rare)Less often
How to diagnose & fix
Work through it in order
- Read freeze-frame and confirm the fault is the auxiliary pump control circuit driven high.
- Inspect the pump connector and wiring for damage, corrosion, or shorts to power.
- Check the pump's power, ground, and control signal with the key on.
- Test the auxiliary pump itself for a coil open or short.
- Repair wiring or replace the pump/relay as needed, then clear and re-test.
FAQ
Quick answers
Is it safe to drive with P2799?+
Usually yes for normal driving, since the engine-driven pump maintains pressure while running. Auto start-stop function is the main thing affected.
Can I just clear P2799?+
It will come back if the wiring fault or pump problem is still present. Fix the circuit first.
Related codes
Read & clear P2799 yourself
Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.
✓ Verified name — SAE J2012 / ISO 15031-6Guidance reviewed by OBD DashX