High Voltage Service Disconnect Circuit Low
The P0B35 code indicates that the Powertrain Control Module (PCM) has detected a low voltage condition in the high voltage service disconnect circuit. This circuit is part of the hybrid/electric vehicle's safety system, designed to isolate the high voltage battery during service. A low voltage reading suggests a fault in the circuit, such as a short to ground, open circuit, or a faulty service disconnect switch. This can prevent the vehicle from entering a safe high-voltage shutdown state, posing a safety risk.
1. Symptoms You Will Notice
- Check Engine Light illuminated
- Hybrid system warning light on
- Vehicle may not start or enter ready mode
- Reduced power or limp mode
2. Most Common Causes
- High voltage service disconnect not fully seated or improperly installed
- Corrosion or contamination on the service disconnect terminals
- Wiring or connector in the service disconnect monitoring circuit shorted to ground
- Excessive resistance in the service disconnect detection circuit
- Internal failure of the high-voltage battery control module or isolation monitoring module
- Faulty or damaged high voltage service disconnect
3. Step-by-Step Diagnosis
Step 1: Use a scan tool to retrieve all stored codes and freeze frame data.
Step 2: Visually inspect the high voltage service disconnect switch and its wiring for damage, corrosion, or loose connections.
Step 3: Using a multimeter, check the resistance and voltage at the service disconnect circuit to identify shorts or opens.
Step 4: If the switch is faulty, replace it and clear the code. If wiring issues are found, repair as necessary.
4. Frequently Asked Questions
Is it safe to drive with this code?▼
No, it is not safe. This code indicates a fault in the high voltage safety system, which could prevent proper isolation of the high voltage battery. Driving may increase the risk of electric shock or component damage. Have the vehicle towed to a qualified technician.
How much does it cost to fix?▼
The cost typically ranges from $50 to $150 for diagnosis and repair, depending on whether the service disconnect switch needs replacement or if wiring repairs are required. Labor rates vary by location.
5. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.