OBD-II Generic Error Code P2798: How to Fix It

Q: Is it safe to drive with a P2798 code?

It is not recommended to drive long distances with a P2798 code active. The auxiliary transmission fluid pump assists in keeping the transmission cool and lubricated. Driving without it functioning properly — especially under heavy load, towing, or in hot weather — risks overheating the transmission, which can cause costly internal damage. Short, low-demand trips to get to a shop are generally okay, but address the issue as soon as possible.

Q: What vehicles commonly get the P2798 code?

P2798 most commonly appears in hybrid vehicles and vehicles with dual-clutch or continuously variable transmissions (CVTs) that use an electrically driven auxiliary fluid pump. Brands such as Toyota, Honda, Ford, General Motors, and Chrysler have models with these systems. Always consult a vehicle-specific service manual, as the exact pump location and circuit specifications vary by make and model.

Q: Can a bad fuse cause P2798?

Yes. A blown fuse in the auxiliary transmission fluid pump circuit is one of the simplest and most common causes of P2798. Always check fuses first before moving on to more complex diagnostics, as a blown fuse is an inexpensive and easy fix.

Q: How much does it cost to fix a P2798 code?

Costs vary widely depending on the root cause. Replacing a fuse or relay may cost just a few dollars. Repairing damaged wiring can range from $50 to $300 depending on labor rates and extent of damage. Replacing the auxiliary transmission fluid pump itself typically costs between $150 and $600 for parts, plus 1–3 hours of labor. PCM diagnosis or replacement is more expensive and can exceed $1,000 at a dealership.

Q: Can low transmission fluid cause P2798?

Low transmission fluid alone is unlikely to directly trigger P2798, but it can stress the auxiliary pump and contribute to related faults. Always check the transmission fluid level and condition as part of your diagnosis. Correcting a low fluid level may also help resolve any related transmission temperature codes appearing alongside P2798.

Abstract

Error code P2798 means the vehicle's powertrain control module (PCM) has detected an abnormally low voltage or signal in the control circuit for the auxiliary transmission fluid pump. This pump helps circulate transmission fluid for cooling and lubrication, especially in hybrid vehicles and those with active cooling systems. If left unaddressed, this fault can lead to overheating of the transmission, increased wear, and potential transmission damage.