B1574 — Door Ajar LR Circuit Short To Ground

B1574 — Door Ajar LR Circuit Short To Ground. A fault in the body electrical system. The car is usually drivable while you plan the repair. Typical causes: faulty switch, motor or actuator of the affected system, damaged wiring in door jambs or wet areas, 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 B1574 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 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 B1574 does not return.

Approximate repair cost

Repair cost depends on which component actually failed. Typical scenarios for B1574 (parts and labor, USD, independent shop rates): Repair wiring or connectors: $80–$250; Replace the switch or actuator: $120–$450; BCM repair or replacement: $300–$900. Overall, fixing B1574 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 B1574 mean?

Is it safe to drive with B1574?

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.

What is the most common cause of B1574?

The most common causes are: faulty switch, motor or actuator of the affected system, damaged wiring in door jambs or wet areas, corroded or loose connectors.

How do I diagnose B1574 myself?

Start with a scan: confirm B1574, save the freeze frame and note any companion codes. Then inspect the wiring and connectors related to the body electrical system, and verify the suspect component against live data before buying parts.

How much does it cost to fix B1574?

Repair wiring or connectors — $80–$250; Replace the switch or actuator — $120–$450; BCM repair or replacement — $300–$900. Exact cost depends on the root cause, your vehicle and local labor rates — a proper diagnosis is the cheapest first step.

When your scan tool pulls code B1574, the vehicle's control module is reporting a specific electrical fault in the body system: a short circuit to ground on the left-rear door ajar circuit. This falls within the body electrical category of OBD2 codes, which handle everything from door switches and lighting to power windows and central locking. Unlike powertrain codes, B1574 won't cause stalling or trigger limp-home modes, but it can leave certain comfort and security features partially or fully inoperative.

The module doesn't set B1574 based on a single momentary glitch. It requires the fault condition to appear consistently under specific operating parameters before the check engine light activates. When B1574 is stored, the associated freeze frame data captures engine load, RPM, coolant temperature, and vehicle speed at the exact moment of detection. That snapshot is your roadmap—recreate those exact conditions during diagnosis and you'll catch the fault every time.

The door ajar switch itself is a simple spring-loaded mechanism. When the left-rear door closes, the switch compresses and signals the body control module that the circuit is complete and the door is secured. When the door opens, the switch releases and the circuit opens. A short to ground tells the BCM the door is always open, even when it's latched. This confuses the module and can trigger the interior light, disable the central locking, or prevent the ignition from recognizing an open door condition.

Common Symptoms of B1574

The left-rear door ajar indicator stays illuminated on the instrument cluster regardless of door position
Interior dome lights remain on when they should shut off
Central locking operates erratically or fails to lock/unlock all doors
Power window controls may become unresponsive on affected door
The alarm system fails to arm properly due to incorrect door status signal
No effect on engine performance, fuel economy, or emissions systems in most cases
Check engine or warning light remains on after clearing codes

What Causes B1574?

Corrosion or moisture intrusion at the door jamb connector causes the switch signal wire to short to ground
Wiring insulation worn through from repeated flexing at the door hinge point
The door ajar switch itself failed internally and grounds the signal circuit
Loose or pushed-back connector pins creating intermittent short conditions
Blown fuse protecting the door ajar circuit in the interior fuse panel
Water damage from a leaking door seal migrating down the wiring harness
Body control module interpreting phantom signals due to internal circuit failure

How to Diagnose B1574

Connect an OBD2 scanner and confirm B1574 is actively stored, then record all freeze frame data before clearing anything—the snapshot of engine conditions when the fault occurred guides your entire diagnostic path.
Pull all related codes alongside B1574; secondary codes often point directly to the failing component rather than the circuit itself. Search your manufacturer's technical service bulletins using your VIN at nhtsa.gov or the brand's owner site—many body electrical codes have published factory fixes or software recalibrations.
Perform a thorough visual inspection of the left-rear door jamb wiring harness, looking for cracked insulation, green corrosion growth, bent connector pins, and any signs of water staining along the wire boots.
Access the door ajar switch connector and test for unwanted resistance or continuity to ground on the signal circuit using a multimeter—compare readings with the door both open and closed.
Operate the door while monitoring live data on your scan tool, watching the door status PID to see if it responds correctly or if it shows "open" constantly despite the door being closed.
Clear B1574 after repairs, then drive through a complete cycle including the exact conditions from your freeze frame data to verify the code doesn't return.

Repair Options and Costs

The repair strategy depends entirely on which component is actually at fault. Most technicians recommend working from least to most expensive:

Wiring harness repair or connector replacement: $80–$250
Door ajar switch replacement: $120–$450
Body control module repair or replacement: $300–$900

Total Cost to Fix B1574

For parts and labor at independent shop rates, expect these typical scenarios for B1574 in USD: simple wiring repair runs $80–$250, switch replacement typically costs $120–$450 depending on vehicle make, and BCM issues land in the $300–$900 range when the module requires replacement. Most cases of B1574 resolve in the $120–$250 bracket once the faulty switch or damaged wiring is identified. Always insist on a confirmed diagnosis before authorizing expensive module replacement— BCM failure accounts for a small percentage of actual B1574 cases despite being the most costly repair path.

Can You Drive with B1574?

B1574 presents minimal risk to drivability or vehicle safety in most circumstances. The engine will start, run, and accelerate normally. However, the fault can leave exterior lighting functions impaired if the short affects shared circuits, and central locking problems may prevent you from securing the vehicle properly. If the interior lights stay on constantly, you risk draining the battery on older vehicles. Address the underlying cause promptly even if the car seems drivable—prolonged shorts can eventually damage the body control module itself.