P2799 — Transmission fluid pump electrical circuit issue

The transmission's auxiliary fluid pump control circuit is reporting a high voltage or electrical fault. This usually means the pump is not operating correctly, which can affect transmission fluid pressure and shifting performance.

Common causes

The cause is almost always one of a few things. Here they are — P2799 rarely comes from anything outside this list:

• Damaged or corroded wiring/connectors in pump circuit
• Faulty auxiliary transmission fluid pump
• Transmission control module malfunction
• Blown fuse or relay related to pump circuit

Where to start

In the order a sensible mechanic would work — the cheap checks first, the expensive replacements only after:

1. Inspect and repair wiring and connectors for damage or corrosion
2. Check and replace blown fuses or relays
3. Test and replace auxiliary transmission fluid pump if faulty
4. Scan and reprogram or replace transmission control module if needed

That is what holds for P2799 in general. From here it depends on your engine — tell me which car it is and what it does, and I will give you the steps for it: real procedures, torque figures and diagrams instead of general advice.