B1572 — Door Ajar LR Circuit Open

B1572 — Door Ajar LR Circuit Open. A fault in the body electrical system. The car is usually drivable while you plan the repair. Typical causes: blown fuse or failed relay, faulty switch, motor or actuator of the affected system, corroded or loose connectors.

body electrical

Is it safe to drive?

Short-term driving is OK Usually safe to drive — body codes rarely affect drivability. Exceptions: exterior lighting and wipers in bad weather, and central locking faults that can leave the car unsecured.

How to diagnose with an OBD scanner

Read the code and freeze frame Connect an OBD2 scanner, confirm B1572 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 B0xxx 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 body electrical system for damage, corrosion, chafing or poor contact.
Subsystem check Do a continuity test end-to-end on the door ajar LR circuit and wiggle the harness while measuring — intermittent opens show up as fluctuating readings.
Subsystem check Operate the affected function while watching its switch and motor PIDs in live data.
Subsystem check Inspect connectors and wiring at flex points (door jambs, tailgate hinges) — wires break there first.
Verify the repair Clear the code, complete a full drive cycle including the conditions from the freeze frame, and confirm B1572 does not return.

Approximate repair cost

Repair cost depends on which component actually failed. Typical scenarios for B1572 (parts and labor, USD, independent shop rates): BCM repair or replacement: $300–$900; Replace the switch or actuator: $120–$450; Repair wiring or connectors: $80–$250. Overall, fixing B1572 usually costs between $80 and $900. An accurate diagnosis before buying parts saves money — the most expensive scenario is rarely the first one to check.

Common questions

What does OBD2 code B1572 mean?

What are the symptoms of B1572?

Drivers most often notice: the affected function (locks, windows, lighting, wipers) works intermittently or not at all, warning light on the dashboard, no impact on engine operation in most cases.

How do I diagnose B1572 myself?

Start with a scan: confirm B1572, save the freeze frame and note any companion codes. Then inspect the wiring and connectors related to the door ajar LR, and verify the suspect component against live data before buying parts.

Will B1572 clear itself?

Sometimes B1572 clears after a few drive cycles if the fault was intermittent — for example a loose connector or a tank of bad fuel. The underlying cause usually remains, so the code tends to return. Clear it once; if it comes back, diagnose rather than erase it repeatedly.

Is it safe to drive with B1572?

Usually safe to drive — body codes rarely affect drivability. Exceptions: exterior lighting and wipers in bad weather, and central locking faults that can leave the car unsecured.

B1572 – Door Ajar LR Circuit Open

When the diagnostic scanner retrieves code B1572, it is flagging a specific electrical fault within the vehicle's body control system. The code points to an open circuit condition affecting the left-rear door ajar circuit. In practical terms, this means the electrical pathway that monitors or operates the left-rear door ajar function has lost its ability to carry current — the circuit is broken somewhere along its route.

Modern vehicles rely on the body control module to continuously monitor door positions through low-current circuits. The module sends a reference signal down the wire and expects to receive it back through the door ajar switch or sensor. When that return signal disappears, the module logs B1572 and captures a freeze frame — a snapshot recording engine RPM, calculated load, coolant temperature, and vehicle speed at the exact moment the fault occurred. This data proves invaluable during diagnosis because it reveals the conditions under which the circuit failed, helping technicians replicate the problem rather than chasing symptoms that only appear under specific circumstances.

An open circuit can occur anywhere along the door ajar LR wiring route. The break may be in the harness running through the door jamb, inside a connector that has backed out or corroded, or within the door ajar switch or actuator itself. In some cases a blown fuse interrupts the circuit upstream, while in others the body control module is the actual source of the problem. Locating the exact break requires systematic testing, but the underlying issue is always the same — current cannot complete its intended path.

Common Symptoms of B1572

Left-rear door position sensor reports erratically or fails to update
Interior lights may stay on or fail to activate when the door opens
Instrument cluster displays a door-ajar warning that does not match actual door position
Central locking system behaves unpredictably, particularly affecting rear door locks
Check-engine or body-system warning light illuminates on the dashboard
Affected function operates intermittently or does not respond at all

What Causes B1572

Faulty door ajar switch or actuator in the left-rear door
Wiring harness damage in areas of repeated flexing, especially the door jamb
Connector pins that are corroded, bent, or pushed out of position
Broken or severed wires hidden within the door harness
Blown fuse feeding the door ajar circuit
Moisture intrusion causing corrosion at connectors in wet areas
Failed relay controlling the body electrical subsystem
Body control module itself malfunctioning or suffering internal damage

How to Diagnose B1572

Connect an OBD2 scanner and confirm B1572 is stored. Record the freeze frame data — it documents engine conditions present when the module first detected the open circuit and guides which driving scenarios to recreate during testing.
Check for any related diagnostic trouble codes in the body electrical system. Multiple codes often point to a common source such as a shared power feed or ground. Review manufacturer technical service bulletins for your specific make and model, as certain B-codes have known root causes documented by the factory.
Perform a visual inspection of the left-rear door wiring harness and all associated connectors. Look for chafed insulation, broken strands inside the wire, green or white corrosion buildup, and any connectors that are not fully seated.
Using a digital multimeter, check continuity along the entire door ajar LR circuit from the body control module to the switch. Gently wiggle the harness during testing — an intermittent open will show as fluctuating resistance or an open circuit only when the wire is moved.
Observe live data from the door ajar switch PID while physically opening and closing the left-rear door. The status should change reliably with each position. If the PID remains stuck on or off regardless of door position, the switch or wiring is faulty.
Pay close attention to the hinge-side door wiring passage. Wires flex every time the door opens and closes, making this the most common location for fatigue breaks. Also inspect the connector at the door body junction for bent pins or corrosion blocking the signal.
After completing repairs, clear the code and drive the vehicle through a complete drive cycle that reproduces the conditions recorded in the freeze frame. If B1572 does not return, the repair is confirmed. Persistent codes indicate additional hidden damage that requires further circuit investigation.

Repair Options for B1572

Once the specific failing component is identified, repair paths diverge by cost and complexity. If the door ajar switch or actuator is defective, replacement typically runs $120–$450 depending on the part price and labor time for your vehicle. Repairing damaged wiring or corroded connectors usually costs $80–$250 when the shop can access and rework the existing harness. In cases where the body control module itself is faulty, BCM repair or replacement ranges from $300–$900, though this is the least common scenario and should only be considered after all wiring and switches have been ruled out.

How Much Does It Cost to Fix B1572?

The total repair bill hinges entirely on which part of the circuit failed. Based on independent shop labor rates in the United States, expect to pay $120–$450 to replace a faulty door ajar switch or actuator. Wiring harness repairs or connector cleaning run $80–$250 in most cases. A body control module repair or replacement — the most expensive scenario — typically costs $300–$900. Putting these together, fixing B1572 generally falls between $80 and $900 depending on the root cause. The most practical approach is to invest in a proper diagnosis first and work through the least expensive likely causes before committing to a module replacement.

Can You Drive with B1572?

B1572 is classified as a body system fault with minimal direct impact on engine operation, so most drivers can continue operating the vehicle safely in the short term. The circuit does not control throttle, braking, or steering. However, the underlying fault can produce secondary effects worth considering. A door that the module believes is open may leave interior lights on, draining the battery over time. If the fault affects the central locking circuit, the vehicle may not lock reliably. In cases where exterior lighting or windshield wipers share the affected circuit, visibility could be compromised during inclement weather. Address the fault within a reasonable timeframe to prevent these side effects from becoming inconvenient or hazardous.