Service disconnect plug not fully seated or latched in its socket.; Corroded or damaged terminals at the service disconnect connector.; Broken or chafed wiring in the high-voltage interlock loop.; Faulty service disconnect switch internal contacts.; Failed high-voltage interlock loop resistor or sensor.; Battery energy control module software or hardware fault misinterpreting the signal.

DTC codes / P0Bxx · Hybrid propulsion / P0B37

P0B37High Voltage Service Disconnect Open

Q: What does code P0B37 mean?

High Voltage Service Disconnect Open. P0B37 indicates that the high-voltage service disconnect circuit has been detected as open when the battery energy control module expected it to be closed, meaning the high-voltage path is interrupted. The computer monitors the voltage or continuity across the service disconnect switch and sets this code when the signal falls outside the expected range for the high-voltage interlock loop.

P0B37 indicates that the high-voltage service disconnect circuit has been detected as open when the battery energy control module expected it to be closed, meaning the high-voltage path is interrupted. The computer monitors the voltage or continuity across the service disconnect switch and sets this code when the signal falls outside the expected range for the high-voltage interlock loop.

SystemPowertrain

Code typeGeneric (all makes)

SeverityHigh

Fix difficultyProfessional

AreaHybrid propulsion

Symptoms you may notice

Often no symptoms besides the warning light, especially if the vehicle still runs on the internal combustion engine.
The high-voltage battery may not charge or the vehicle may fail to start in electric mode.
A message on the dash may instruct the driver to service the high-voltage system immediately.
The vehicle may enter a reduced power or limp mode.
The high-voltage contactors may not close, preventing the battery from supplying power to the drivetrain.

Common causes, most likely first

Service disconnect plug not fully seated or latched in its socket.
Corroded or damaged terminals at the service disconnect connector.
Broken or chafed wiring in the high-voltage interlock loop.
Faulty service disconnect switch internal contacts.
Failed high-voltage interlock loop resistor or sensor.
Battery energy control module software or hardware fault misinterpreting the signal.

How to diagnose and fix it

Verify the service disconnect plug is fully inserted and the locking tab is engaged.
Inspect the service disconnect connector and terminals for corrosion, damage, or loose pins; clean or repair as needed.
Check the high-voltage interlock loop wiring for continuity and shorts, repairing any damaged sections.
Test the service disconnect switch for proper continuity in the closed position, replacing it if faulty.
Measure the interlock loop resistance and compare to specification; replace the resistor or sensor if out of range.
Clear the code and perform a road test to confirm the repair; if the code returns, follow the manufacturer's diagnostic flow for the battery energy control module.

Service disconnect faults that fool technicians

A service disconnect that looks fully seated can still have an open interlock circuit because the small signal pins in the connector are bent or pushed back, so always verify pin fitment and terminal drag.
The high-voltage interlock loop often includes the service disconnect, the battery pack cover, and other safety switches in series, so an open elsewhere in the loop can set P0B37 even if the disconnect itself is fine.
Some vehicles set this code after a low-voltage battery replacement or jump-start if the service disconnect was disturbed during the procedure, and a simple reseat and clear may resolve it.
The code can be stored intermittently by water intrusion into the service disconnect connector, which causes corrosion that only acts up in damp conditions; a visual inspection in dry weather may miss it.
Do not assume the service disconnect is the root cause just because the code points there; the battery energy control module can misreport an open circuit if its internal reference voltage is unstable.

Can I keep driving with P0B37?

Do not continue driving with this code active because the high-voltage system may be disabled, leaving the vehicle without electric propulsion and potentially causing a stall or loss of power. Have the vehicle inspected by a qualified high-voltage technician before driving further.

Tools that help

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Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.