P2798
Electric/Auxiliary Transmission Fluid Pump A Control Circuit Low
Transmission (auxiliary fluid pump)
Generic OBD-II
Medium
What it means
P2798 means the transmission controller detects low voltage on the control circuit for the auxiliary (electric) transmission fluid pump. That pump keeps transmission line pressure up when the engine auto-stops on stop-start and hybrid systems. With it not driven properly you can get harsh engagements after restarts and loss of the stop-start feature; it is generally not a no-start.
Medium
Can I keep driving? Usually yes, but on stop-start/hybrid vehicles you may get harsh re-engagement after an auto-restart and auto stop-start may be disabled; avoid heavy use until fixed.
Common symptoms
What you'll notice
- Harsh or delayed engagement after a stop-start auto-restart
- Auto stop-start disabled or warning displayed
- Possible transmission overheating during heavy low-speed use
- Check-engine light on with the code stored
Common causes
Most likely first
- Open, shorted-to-ground, or high-resistance wiring to the auxiliary pumpLikely
- Corroded or loose auxiliary-pump connectorCommon
- Faulty auxiliary transmission fluid pump or its control driver/relayCommon
- Blown fuse feeding the auxiliary pump circuitLess often
How to diagnose & fix
Work through it in order
- Check the auxiliary-pump fuse and connector for corrosion or looseness.
- Measure the control circuit for opens, shorts to ground, and voltage drop against spec.
- Command the pump with a scan tool (if supported) and confirm it runs and draws normal current.
- Replace the auxiliary pump or repair the wiring/driver as indicated, then clear and re-test.
FAQ
Quick answers
Is it safe to drive with P2798?+
Generally yes for normal driving. The main effects are loss of stop-start and possible harsh restarts; avoid extended heavy low-speed towing until repaired.
Can I just clear P2798?+
It returns if the circuit fault is still present. Repair the wiring or pump so the auxiliary pump is controlled correctly.
Related codes
Often seen with P2798
Read & clear P2798 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