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, allowing technicians to safely disable the high voltage battery during service. A low voltage reading suggests a fault in the wiring, connector, or the service disconnect switch itself, potentially compromising the ability to safely isolate the high voltage system.
01. Most Common Causes
- Faulty high voltage service disconnect switch
- Open or shorted wiring in the service disconnect circuit
- Corroded or damaged connector at the service disconnect
- Failed PCM (rare)
02. Symptoms You Will Notice
- Check Engine Light illuminated
- Hybrid system warning light on
- Vehicle may not start or enter ready mode
- Reduced performance or limp mode
03. 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 digital multimeter, check the voltage at the service disconnect circuit per manufacturer specifications.
Step 4: If voltage is low, isolate the circuit and test continuity of wires and the switch itself.
Step 5: Replace any faulty components and clear the code, then test drive to verify repair.
04. Commonly Affected Makes
05. Frequently Asked Questions
Is it safe to drive with this code?▼
No, it is not recommended. This code indicates a potential safety issue with the high voltage system, which could lead to unexpected shutdown or inability to disable the battery in an emergency.
How much does it cost to fix?▼
The cost typically ranges from $100 to $300, depending on the cause. Replacing the service disconnect switch is usually around $150-$250, while wiring repairs may be less.