B3137 – All Door Lock Circuit Low (BCM)

System: Body | Standard: ISO/SAE Controlled | Fault type: Circuit Low

Definition source: SAE J2012/J2012DA (industry standard)

B3137 – B3137 – All Door Lock Circuit Low (BCM)

B3137 means the body control module (BCM) has detected that the electrical circuit used to command or monitor the all-door lock function is reading lower than expected (a “circuit low” condition). In real-world terms, this B3137 code commonly shows up when the power lock system behaves inconsistently—doors may not lock from the switch, remote, or automatic locking feature, or they may lock only sometimes. Because this is a body (not powertrain) diagnostic code, it does not affect engine drivability or emissions directly, but it can create a security and safety inconvenience. The exact circuit and expected voltage depend on the vehicle’s wiring design, so confirm with a wiring diagram and testing.

B3137 indicates the BCM is seeing an abnormally low voltage on the all-door lock circuit, usually caused by a short-to-ground, excessive resistance/voltage drop, or a connector/wiring fault that prevents the lock command signal from reaching the expected level.

What Does B3137 Mean?

The meaning of B3137 is that the BCM’s door lock input/output circuit for locking all doors is not achieving the voltage level the module expects during operation. “Circuit low” points to the signal being pulled toward ground or being dragged down by resistance (corrosion, damaged wiring, poor terminal tension), rather than being “open” or “high.” Depending on vehicle design, the BCM may set B3137 when it commands the lock function and sees the feedback stay low, or when it monitors a lock request line that is stuck low longer than allowed.

Theory of Operation

Under normal operation, the BCM interprets a lock request (from a driver door switch, key fob receiver, or other body network request) and then drives the door lock circuits through internal drivers or external relays. Many systems use a momentary command: the BCM applies voltage to a control circuit or switches ground to energize lock actuators/relays for a short time, then releases it. The BCM may also monitor the command circuit’s voltage to confirm it changes state when commanded.

With B3137 (circuit low), the BCM detects the lock circuit voltage is lower than the calibrated threshold when it should be higher. Common electrical explanations include a short to ground, a partially grounded wire due to chafing, water intrusion in a connector, or excessive voltage drop from corrosion or a weak/loaded supply. Because designs vary, confirm whether the circuit is BCM-supplied voltage, BCM-switched ground, or a monitored input line before testing.

Symptoms

• Power locks inoperative: doors may not lock from the driver/passenger lock switch.
• Remote locking inconsistent: key fob lock command may work intermittently or only at certain doors.
• Auto-lock feature malfunction: automatic locking (if equipped) may fail to engage or behave unpredictably.
• Lock cycle incomplete: locks may “click” but not fully lock due to low command voltage or a dragged-down control circuit.
• Intermittent operation over bumps: vibration may change circuit resistance at a loose terminal or damaged wire, triggering B3137 symptoms on and off.
• Security/door status warnings: the vehicle may display body-related warnings or chimes if the lock command cannot be executed reliably.

Common Causes

• Cause: Door lock control circuit short to ground (chafed insulation, pinched harness in a door jamb boot, or rubbed-through wiring)
• Cause: High resistance/voltage drop in the lock control circuit that pulls the signal low under load (corroded splice, partially broken wire strands, water intrusion)
• Cause: Short to ground inside a door lock actuator/lock solenoid or latch assembly (internal winding or driver path dragging the circuit low)
• Cause: Connector/terminal problems at the BCM or door harness (backed-out pin, spread terminal, corrosion creating an unintended ground path)
• Cause: Shared ground issue affecting the door lock circuit behavior (loose ground fastener, corrosion at ground point, increased ground resistance causing abnormal low readings)
• Cause: Aftermarket equipment or recent repairs interacting with the lock wiring (alarm/remote start/tint/door work that introduced a ground tap or damaged the harness)
• Cause: Moisture intrusion in a door module/harness junction causing leakage to ground (wet connector cavities, condensation, salt contamination)
• Cause: BCM internal driver or circuit fault (rare; consider only after proving wiring and loads are correct with testing)

Diagnosis Steps

Use a scan tool that can access Body/BCM codes and view door lock command data, a digital multimeter (DVOM) for voltage drop and continuity checks, and an accurate wiring diagram for the all-door lock control circuits. A test light or fused jumper can help load-test the circuit safely. Back-probe pins and use T-pins to avoid terminal damage.

1. Verify the complaint: confirm whether lock/unlock functions fail on all doors or intermittently, and note if the issue occurs only from the switch, only from the key fob, or both.
2. Scan the BCM for B3137 and any additional body codes; record freeze-frame/snapshot data if available and note if the code sets during a lock command, unlock command, or at key-on.
3. Clear codes and command the door locks with the scan tool (if supported) and from the interior switch; see when B3137 returns. This helps separate a constant short-to-ground from a fault that appears only when the circuit is driven.
4. Perform a focused visual inspection of the door jamb boots and harness routing on both sides; look for crushed sections, previous repairs, exposed copper, and areas that flex with door movement.
5. Inspect BCM and door harness connectors for corrosion, moisture, or damaged terminals. Gently tug-test suspect wires at the connector; check for backed-out pins and terminal spread that can cause unintended grounding.
6. With locks at rest, measure the voltage on the all-door lock control circuit at the BCM connector (back-probe). A “circuit low” fault typically shows the line pulled near 0V when it should not be, pointing to a short to ground or heavy leakage.
7. Perform a load test: command LOCK/UNLOCK while monitoring circuit voltage. If voltage collapses immediately toward 0V when commanded, suspect an overloaded circuit (shorted actuator/solenoid) or a hard short to ground.
8. Isolate the fault by disconnecting loads one at a time (door lock actuator connectors or door harness connectors, depending on the wiring design). Re-check the control circuit voltage/behavior after each disconnection to see when the low condition disappears.
9. Check continuity to ground with power off (battery disconnected if required by service info). If the control circuit shows near-zero resistance to ground, locate the short by sectioning the harness (door-to-body connector, splice points, and door harness branches).
10. Measure voltage drop on grounds used by the door lock system while commanding locks (DVOM across ground point to battery negative). Excessive drop indicates ground path problems that can distort circuit readings and trigger B3137.
11. If wiring and loads test good, verify BCM power and ground integrity (key-on and during lock commands). Poor BCM supply/ground can cause incorrect low-circuit detection.
12. Only after confirming correct wiring, connector integrity, loads, and BCM power/ground, consider BCM internal driver fault as a last step and follow OEM procedures for confirmation.

Professional tip: Don’t rely on an ohmmeter alone for B3137. A circuit can look “fine” for continuity but still pull low under load due to corrosion or a partially broken wire. Use voltage drop and command the locks while measuring to catch real-world failures.

Possible Fixes

• Repair chafed/pinched door lock control wiring and protect it with proper loom and routing in the door jamb area
• Clean, dry, and restore BCM/door harness connectors; repair or replace damaged terminals and apply appropriate connector sealing where specified
• Repair corroded splice points or high-resistance sections causing voltage drop that drags the circuit low
• Replace a faulty door lock actuator/solenoid or latch assembly found to be internally shorted or overloading the circuit
• Restore ground integrity (clean and tighten ground points; repair ground wires) and retest under load
• Remove/repair aftermarket wiring modifications that introduce unintended ground paths or overload the lock circuit
• Replace or reprogram the BCM only after all circuit and load tests confirm the module is at fault (rare)

Can I Still Drive With B3137?

In most cases, yes—you can still drive with a B3137 code because it’s a body (BCM) electrical fault, not a powertrain or braking fault. However, it may not be safe or practical to ignore because the all-door lock control circuit is being detected at an abnormally low voltage (typically consistent with a short-to-ground or heavy voltage drop). That can cause the power locks to behave unpredictably, not respond, or repeatedly lock/unlock, and it may drain the battery if the circuit is being pulled low continuously. If you can’t reliably lock the doors or the locks cycle on their own, address B3137 promptly for security and to prevent a no-start from a discharged battery.

How Serious Is This Code?

B3137 is usually a low-to-moderate severity fault, but it becomes more serious when it causes repeated lock actuator activity, BCM wake-ups, or continuous current draw. The biggest real-world risks are battery drain, loss of reliable door locking (security/safety), and potential overheating of wiring or a lock actuator if the circuit is being held low due to a short-to-ground. It typically won’t affect drivability, emissions, or engine performance, but it can strand you if the battery dies or if the vehicle can’t be secured. If B3137 appears with other body electrical codes, the chance of a shared wiring/ground problem increases and should be treated with higher urgency.

Repair Costs

Last updated: March 21, 2026