What Does B1571 Mean?
This code indicates the Body Control Module (BCM) has detected a circuit malfunction in the left rear (LR) door ajar switch or its associated wiring. The BCM monitors the door ajar switches to determine when doors are open or closed for interior lighting, security systems, and instrument panel warnings. A circuit failure means the BCM cannot reliably read the status of the left rear door position due to an open circuit, short circuit, or faulty switch.
Common Causes
45%
Faulty or corroded left rear door ajar switch/latch assembly
30%
Damaged, chafed, or broken wiring between door jamb and BCM
15%
Corroded or loose connector at door switch or BCM
10%
Failed Body Control Module internal circuit
Diagnostic Steps
1
Step 1: Visually inspect the left rear door ajar switch in the door jamb for physical damage, corrosion, or loose mounting. Check switch plunger operation for smooth movement and proper return spring function.
2
Step 2: Using a digital multimeter, test the door ajar switch directly at the switch connector with door open and closed. Switch should show continuity to ground when door is open, and open circuit when door is closed (or vice versa depending on switch type).
3
Step 3: Inspect wiring harness from left rear door jamb through door hinge area to BCM for chafing, cuts, or damage. Pay special attention to flex points where door opens and closes. Check all connectors for corrosion, bent pins, or moisture intrusion.
4
Step 4: Using the multimeter, perform continuity test on the circuit from BCM connector to door switch connector with harness disconnected at both ends. Resistance should be less than 1 ohm. Also check for shorts to ground or power with door switch disconnected.
5
Step 5: Monitor live data on scan tool while manually actuating the door switch. Verify BCM recognizes state changes. If wiring and switch test good but BCM does not respond, suspect BCM internal fault.
6
Step 6: After repairs, clear codes, cycle the left rear door open and closed multiple times, and verify door ajar indicator and interior lights function correctly. Re-scan for codes to confirm repair.
Estimated Repair Cost
$75 - $400
Parts + labor, varies by vehicle and location
This code indicates the Body Control Module (BCM) has detected a circuit malfunction in the left rear (LR) door ajar switch or its associated wiring. The BCM monitors the door ajar switches to determine when doors are open or closed for interior lighting, security systems, and instrument panel warni...
The most common cause of B1571 (Door Ajar LR Circuit Failure) is: Faulty or corroded left rear door ajar switch/latch assembly
Typical repair costs for B1571 range from $75 to $400, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Safe to drive as this does not affect vehicle operation or safety systems. Primary concern is interior lights may stay on draining the battery, security system may not arm properly, and dashboard warning light will remain illuminated causing driver distraction.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to B1571 to identify the root cause.
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Quick Info
Category
Body
System
Body Control and Convenience Systems
Difficulty
Type
Manufacturer
Recommended Tools
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