Auxiliary Transmission Fluid Pump Performance Issue
The P2797 code indicates that the auxiliary transmission fluid pump, which is used to maintain fluid pressure when the engine is off (e.g., during stop-start events), is not performing as expected. This pump is critical for ensuring immediate lubrication and pressure upon restart, preventing transmission damage. The powertrain control module (PCM) detects a discrepancy between commanded and actual pump speed or pressure, often due to electrical faults, mechanical failure, or low fluid level.
1. Most Common Causes
- Faulty auxiliary transmission fluid pump
- Low transmission fluid level or contamination
- Wiring or connector issues (open/short) in pump circuit
- Failed PCM or transmission control module
2. Symptoms You Will Notice
- Check Engine Light illuminated
- Transmission slipping or harsh shifting
- Delayed engagement when restarting after stop-start event
- Transmission overheating or warning messages
3. Step-by-Step Diagnosis
Step 1: Scan for additional codes and check freeze frame data.
Step 2: Inspect transmission fluid level and condition; top up or replace if necessary.
Step 3: Visually check wiring and connectors to the auxiliary pump for damage or corrosion.
Step 4: Test pump operation using a scan tool to command it on and monitor current draw or pressure.
Step 5: If pump fails electrical tests, replace the auxiliary pump and clear codes.
4. Frequently Asked Questions
Is it safe to drive with this code?▼
It is not recommended to drive long distances, as the auxiliary pump failure can lead to transmission damage, especially in stop-start traffic. Have it diagnosed promptly.
How much does it cost to fix?▼
Repair costs typically range from $200 to $800, depending on the cause. Pump replacement parts cost $100-$400, plus labor. Fluid change may add $100-$200.
5. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.