Hydraulic Pump Relay Circuit High
The P0948 code indicates that the powertrain control module (PCM) has detected a high voltage condition in the hydraulic pump relay control circuit. This relay controls power to the hydraulic pump used in automatic transmissions or brake systems. A high voltage reading suggests a short to battery voltage, a faulty relay, or a wiring issue. This can lead to improper pump operation, affecting transmission shifting or brake assist.
1. Symptoms You Will Notice
- Check Engine Light illuminated
- Transmission shifting issues or harsh engagement
- Brake assist malfunction (if applicable)
- Hydraulic pump running continuously or not at all
2. Most Common Causes
- Faulty hydraulic pump relay stuck in the open position
- Short to voltage in the relay control circuit wiring
- Corroded, damaged, or loose electrical connections at the relay or control module
- Damaged PCM or TCM with internal circuit driver failure
- Poor ground connection in the relay control circuit
3. Step-by-Step Diagnosis
Step 1: Scan for codes and record freeze frame data.
Step 2: Visually inspect the hydraulic pump relay and its wiring for damage or corrosion.
Step 3: Test relay operation using a multimeter; check for voltage at the relay coil and switch terminals.
Step 4: Check for shorts to battery voltage in the control circuit from PCM to relay.
Step 5: If wiring and relay are good, test PCM output for proper voltage; replace PCM if faulty.
4. Frequently Asked Questions
Is it safe to drive with this code?▼
It is not recommended. Driving may cause transmission damage or loss of brake assist, leading to unsafe conditions.
How much does it cost to fix?▼
Typically $50-$150 for relay replacement and wiring repair. PCM replacement can cost $500-$1000.
5. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.