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 stop-start events or low engine RPM. The powertrain control module (PCM) monitors the pump driver circuit for proper voltage and current. A performance fault means the circuit is not operating within expected parameters, which can lead to insufficient fluid flow and potential transmission damage.
01. Most Common Causes
- Faulty auxiliary transmission fluid pump
- Open or shorted wiring in the pump driver circuit
- Failed pump relay or fuse
- Corroded or loose electrical connectors
- Defective PCM (rare)
02. Symptoms You Will Notice
- Check Engine Light illuminated
- Transmission overheating
- Harsh or delayed shifting
- Transmission slipping
- Reduced fuel economy
03. Step-by-Step Diagnosis
Step 1: Scan for codes and record freeze frame data.
Step 2: Visually inspect the pump, wiring, and connectors for damage or corrosion.
Step 3: Test the pump relay and fuse with a multimeter.
Step 4: Measure voltage and ground at the pump connector with the engine running.
Step 5: If voltage is present, test the pump by applying direct battery power; if it doesn't run, replace the pump.
04. Commonly Affected Makes
05. Frequently Asked Questions
Is it safe to drive with this code?▼
It is not recommended. Driving with a faulty auxiliary pump can cause transmission overheating and damage, leading to costly repairs.
How much does it cost to fix?▼
The cost typically ranges from $50 to $150 for diagnosis and repair, but can be higher if the pump itself needs replacement.