Auxiliary Transmission Fluid Pump Driver Circuit Performance
The P0C29 code indicates a performance issue in the driver circuit of the auxiliary transmission fluid pump. This pump is responsible for circulating transmission fluid to cool and lubricate the transmission, especially during start-stop events or low-speed operation. The powertrain control module (PCM) monitors the pump's electrical circuit for proper voltage and current. A performance fault means the circuit is not operating within expected parameters, which can lead to inadequate fluid circulation, potential transmission overheating, and reduced component lifespan.
1. Symptoms You Will Notice
- Check Engine Light illuminated
- Transmission overheating or slipping
- Reduced fuel economy
- Hesitation or rough shifting
- Transmission warning message on dashboard
2. Most Common Causes
- Faulty auxiliary transmission fluid pump (internal electric motor seized or worn)
- Open or short circuit in the pump harness (power, ground, or PWM signal)
- Corroded, loose, or damaged pump connector terminals
- Damaged internal driver in the transmission control module (TCM) or powertrain control module (PCM)
- Low or contaminated transmission fluid causing excessive mechanical load
3. Step-by-Step Diagnosis
Step 1: Use an OBD2 scanner to confirm the P0C29 code and check for related codes.
Step 2: Inspect the auxiliary transmission fluid pump fuse and relay; replace if blown.
Step 3: Visually examine the pump wiring and connectors for damage, corrosion, or loose connections.
Step 4: Test the pump circuit with a multimeter for proper voltage and ground.
Step 5: If circuit is okay, test the pump itself by applying direct power and ground to see if it operates.
Step 6: Replace the pump if it fails the bench test; otherwise, check the PCM for faults.
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 overheating and damage. Short trips to a repair shop are acceptable if the transmission is not showing severe symptoms.
How much does it cost to fix?▼
The cost typically ranges from $50 to $150 for parts and labor, depending on whether it's a simple wiring repair or pump replacement. Pump replacement may be higher if the part is expensive.
5. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.