What Does B1572 Mean?
This code indicates the Body Control Module (BCM) has detected an open circuit in the left rear door ajar switch circuit. The BCM monitors door ajar switches to determine if doors are properly closed for interior lighting, security, and vehicle status displays. An open circuit means the electrical pathway between the door switch and BCM is interrupted, preventing proper door status detection.
Common Causes
40%
Faulty or stuck left rear door ajar switch/latch assembly
30%
Broken, corroded, or disconnected wiring harness between door and BCM
20%
Corroded or loose connector at door switch or BCM
10%
Failed Body Control Module
Diagnostic Steps
1
Step 1: Visually inspect the left rear door ajar switch and connector for physical damage, corrosion, or loose connections. Check if the switch plunger moves freely and is not stuck in the open position.
2
Step 2: Using a digital multimeter, backprobe the door ajar switch connector and check for continuity to ground when the switch is manually depressed (door closed position). Should read near 0 ohms closed, infinite ohms open.
3
Step 3: Check wiring harness for continuity from the door switch connector through the door boot/hinge area to the BCM connector. Flex the wiring while testing to identify intermittent breaks, paying special attention to the flexible boot section.
4
Step 4: If wiring and switch test good, measure voltage supply at the switch connector with door open. Verify BCM is providing proper reference voltage (typically 5V or 12V depending on manufacturer).
5
Step 5: If all circuits test normal, suspect BCM internal fault. Monitor switch input signal at BCM connector while manually actuating the switch to confirm BCM is not receiving the signal despite proper switch operation.
6
Step 6: After repair, clear codes, cycle the left rear door open and closed multiple times, and verify the door ajar indicator operates correctly and code does not return.
Estimated Repair Cost
$75 - $400
Parts + labor, varies by vehicle and location
This code indicates the Body Control Module (BCM) has detected an open circuit in the left rear door ajar switch circuit. The BCM monitors door ajar switches to determine if doors are properly closed for interior lighting, security, and vehicle status displays. An open circuit means the electrical p...
The most common cause of B1572 (Door Ajar LR Circuit Open) is: Faulty or stuck left rear door ajar switch/latch assembly
Typical repair costs for B1572 range from $75 to $400, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Safe to continue driving. This code only affects interior lighting, door ajar warnings, and security system functionality. Repair at convenience, though it may cause battery drain if interior lights remain on or prevent proper vehicle locking.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to B1572 to identify the root cause.
OBDHut Mobile App
Scan codes directly from your car with the OBDHut app.
Coming Soon
Quick Info
Category
Body
System
Body Control System
Difficulty
Type
Manufacturer
Recommended Tools
OBD2 Scanner
A quality scan tool helps you read codes, view live data, and clear faults.
