P0B37 — High Voltage Service Disconnect Open

OBD2 code P0B37 flags a problem with the sensor and actuator circuits (high voltage service disconnect open). The car is usually drivable while you plan the repair. Common culprits: poor ground connection, corroded, loose or damaged connector, faulty sensor or actuator of the affected circuit.

powertrain (engine/transmission)

Is it safe to drive?

Short-term driving is OK In most cases the car remains drivable, possibly with reduced performance or a disabled auxiliary system. If symptoms include stalling, no-start or brake/steering warnings, treat it as urgent.

How to diagnose with an OBD scanner

Read the code and freeze frame Connect an OBD2 scanner, confirm P0B37 is stored, and save the freeze frame data — it shows engine conditions when the fault was detected.
Check for companion codes and TSBs Related codes often reveal the real root cause. Also check manufacturer technical service bulletins (TSB) for your make and model — many P0xxx issues have factory fixes or software updates. Search by VIN on the manufacturer site or nhtsa.gov.
Inspect wiring and connectors Visually inspect the wiring harness and connectors related to the high voltage service disconnect open for damage, corrosion, chafing or poor contact.
Subsystem check Measure reference voltage, ground and signal continuity at the component connector.
Subsystem check Wiggle-test the harness while watching the signal in live data — dropouts reveal broken wires.
Verify the repair Clear the code, complete a full drive cycle including the conditions from the freeze frame, and confirm P0B37 does not return.

Approximate repair cost

Repair cost depends on which component actually failed. Typical scenarios for P0B37 (parts and labor, USD, independent shop rates): Replace the faulty sensor or actuator: $150–$500; Repair wiring or connectors: $80–$250; Control module repair: $300–$1,000. Overall, fixing P0B37 usually costs between $80 and $1,000. An accurate diagnosis before buying parts saves money — the most expensive scenario is rarely the first one to check.

Common questions

What are the symptoms of P0B37?

Drivers most often notice: Check Engine Light on, possible limp mode depending on the affected component, increased fuel consumption in some cases, the affected system operates intermittently or not at all.

What does OBD2 code P0B37 mean?

What is the most common cause of P0B37?

The most common causes are: poor ground connection, corroded, loose or damaged connector, faulty sensor or actuator of the affected circuit.

How much does it cost to fix P0B37?

Replace the faulty sensor or actuator — $150–$500; Repair wiring or connectors — $80–$250; Control module repair — $300–$1,000. Exact cost depends on the root cause, your vehicle and local labor rates — a proper diagnosis is the cheapest first step.

Is it safe to drive with P0B37?

In most cases the car remains drivable, possibly with reduced performance or a disabled auxiliary system. If symptoms include stalling, no-start or brake/steering warnings, treat it as urgent.

P0B37 is a hybrid and electric vehicle-specific trouble code that points to a problem with the high voltage service disconnect circuit. This safety-related component is designed to isolate the vehicle's high voltage battery pack whenever service is required. When the powertrain control module detects that this circuit has become open — meaning the safety loop is no longer complete — it logs code P0B37 and turns on the check engine light.

The high voltage service disconnect is usually a manual plug or lever assembly that technicians use to de-energize the battery pack before performing any maintenance. The vehicle's control system constantly monitors this circuit through a feedback loop. If that loop opens unexpectedly during normal driving, the module interprets it as a safety fault. For P0B37 to set permanently, the condition must occur more than once under specific driving parameters; a single glitch typically will not trigger the MIL on its own. When the code does store, the freeze frame data captures engine load, RPM, coolant temperature, and vehicle speed at that exact moment, giving you precise conditions to replicate during diagnosis.

Common Symptoms

Check engine light is illuminated on the dashboard
Vehicle may enter reduced-power or limp-home mode depending on which system is affected
Fuel economy can drop noticeably in some configurations
The affected high voltage component may operate intermittently or fail entirely
Some models disable the hybrid functionality entirely until the fault is cleared

Common Causes

Damaged, corroded, or disconnected wiring in the high voltage service disconnect circuit
Loose or worn connector terminals at the service disconnect or control module
Blown fuse protecting the circuit from overcurrent damage
Failed driver or control circuit inside the powertrain or hybrid control module
Faulty high voltage service disconnect switch or associated sensor
Short-to-ground or open-circuit condition somewhere in the wiring harness
Software calibration error in the control module requiring an update

How to Diagnose P0B37

Connect an OBD2 scanner and confirm P0B37 is present in the stored codes. Save the freeze frame data immediately — this snapshot records the exact engine conditions when the fault first appeared, and you will need those parameters to reproduce the failure during testing.
Review any accompanying trouble codes for the same circuit. Related P0xxx codes in the same system often point directly to the failing component. Check manufacturer TSBs for your specific make and model using the VIN search at nhtsa.gov or the OEM technical portal — some P0B37 issues have documented factory fixes or software recalibrations.
Perform a hands-on visual inspection of all wiring and connectors tied to the high voltage service disconnect. Look for cracked insulation, corrosion buildup, bent pins, or any sign that the harness has chafed against body panels or brackets.
Use a multimeter to check reference voltage, ground integrity, and signal continuity at the connector feeding the service disconnect. Compare your readings against the voltage specifications listed in the service manual for your vehicle.
Conduct a wiggle test on the harness while observing the live data stream on your scanner. Any signal dropout or intermittent loss indicates a broken wire or poor connection that is not visible during static inspection.
After repairs, clear the code and complete a full drive cycle that includes the operating conditions captured in the freeze frame. Confirm that P0B37 does not reappear before considering the diagnosis complete.

Repair Options and Costs

Address the most probable and least expensive root causes before committing to expensive component replacement:

Wiring harness repair or connector replacement: $80–$250. Many P0B37 faults stem from damaged wires or corroded terminals that can be spliced or cleaned at relatively low cost.
Sensor or actuator replacement: $150–$500. If the service disconnect switch itself is mechanically failed or the associated sensor has stopped reporting, part-only pricing varies by application.
Control module diagnosis and repair: $300–$1,000. A failed driver circuit inside the PCM or hybrid control unit may require professional module-level repair or full replacement and reprogramming.

Total Repair Cost Summary

The final bill for P0B37 typically falls between $80 and $1,000 depending on which part actually caused the circuit to open. Most vehicles will only need wiring or connector attention rather than full module replacement. Spending time on a thorough electrical diagnosis before purchasing parts is the most reliable way to avoid unnecessary expense — the highest-cost scenario is rarely where you should start.

Driving Safety Verdict

Severity level: Short — the vehicle usually remains drivable after P0B37 sets, though you may notice limited hybrid functions or a noticeable reduction in available power. Treat any accompanying stalling, no-start condition, or brake/steering warnings as an immediate safety concern and discontinue driving until the fault is resolved.