Auxiliary Transmission Fluid Pump Control Circuit High
The P2799 code indicates that the powertrain control module (PCM) has detected a high voltage condition in the control circuit of the auxiliary transmission fluid pump. This pump is typically used in start-stop systems to maintain transmission fluid pressure when the engine is off. A high voltage reading suggests a short to power, a faulty pump, or a wiring issue.
01. Most Common Causes
- Short to battery voltage in the pump control circuit
- Faulty auxiliary transmission fluid pump
- Damaged wiring or connectors in the pump circuit
- Failed PCM (rare)
02. Symptoms You Will Notice
- Check Engine Light illuminated
- Transmission may not shift properly or go into limp mode
- Start-stop system may be disabled
- Possible transmission overheating or slipping
03. Step-by-Step Diagnosis
Step 1: Scan for other codes and check freeze frame data.
Step 2: Visually inspect the auxiliary pump wiring and connectors for damage or corrosion.
Step 3: Test the pump control circuit voltage with a multimeter; compare to manufacturer specs.
Step 4: Check the pump resistance and operation; replace if faulty.
Step 5: If wiring and pump are good, test the PCM output or reprogram/replace PCM.
04. Commonly Affected Makes
05. Frequently Asked Questions
Is it safe to drive with this code?▼
It is not recommended to drive long distances as the transmission may lose pressure, leading to damage. Limp mode may limit speed.
How much does it cost to fix?▼
Repair costs typically range from $200 to $600, depending on whether the pump or wiring needs replacement. PCM replacement can be more expensive.