Hydraulic Pump Relay Circuit Low
The P0947 code indicates that the Powertrain Control Module (PCM) has detected a low voltage condition in the hydraulic pump relay control circuit. This relay supplies power to the hydraulic pump used in automatic transmissions or brake systems. A low voltage reading suggests a short to ground, open circuit, or faulty relay, which can prevent the pump from operating correctly, leading to transmission or brake performance issues.
01. Most Common Causes
- Faulty hydraulic pump relay
- Blown fuse or wiring issues (short to ground or open circuit)
- Corroded or loose relay connector
- Failed PCM (rare)
02. Symptoms You Will Notice
- Transmission slipping or harsh shifting
- Brake pedal feels hard or requires more effort
- Check Engine Light illuminated
- Hydraulic pump not running or intermittent operation
03. Step-by-Step Diagnosis
Step 1: Use a scan tool to confirm P0947 and check for related codes.
Step 2: Inspect the hydraulic pump relay and its fuse; test relay coil and switch contacts with a multimeter.
Step 3: Check wiring and connectors for damage, corrosion, or shorts; repair as needed.
Step 4: If relay and wiring are good, test the hydraulic pump motor for proper operation.
04. Commonly Affected Makes
05. Frequently Asked Questions
Is it safe to drive with this code?▼
No, it is not safe. A low voltage condition can cause the hydraulic pump to fail, leading to loss of transmission or brake assist, which may result in an accident.
How much does it cost to fix?▼
The cost typically ranges from $50 to $150 for parts and labor, depending on whether the relay, fuse, or wiring needs replacement.