What Does B1573 Mean?
This code indicates the Body Control Module (BCM) has detected a short to battery voltage in the left rear door ajar switch circuit. The BCM is receiving constant battery voltage on the circuit when it should see a ground signal (door closed) or an open circuit (door open). This causes the vehicle to think the left rear door is constantly ajar, triggering interior lights, warning chimes, and potentially preventing proper vehicle security functions.
Common Causes
45%
Damaged or chafed wiring harness in door jamb or hinge area causing short to B+ voltage
30%
Faulty door ajar switch with internal short to power
15%
Water intrusion or corrosion in door ajar switch connector causing voltage leak
10%
BCM internal fault or damaged connector terminal creating false voltage reading
Diagnostic Steps
1
Step 1: Visually inspect the left rear door jamb wiring harness for visible damage, chafing, or pinched wires where the harness routes through the door hinge area. Flex the harness while monitoring for intermittent code behavior.
2
Step 2: Disconnect the left rear door ajar switch connector and measure voltage at the BCM side of the circuit with a digital multimeter. Should read 0 volts with switch disconnected; if battery voltage is present, the short is in the wiring harness between the switch and BCM.
3
Step 3: If no voltage found at disconnected switch, test the door ajar switch itself by measuring resistance across terminals. With door closed, resistance should be low (near ground); with door open, should be open circuit. If constant battery voltage is present at switch terminals, replace the switch.
4
Step 4: Inspect the BCM connector pins for the door ajar circuit for corrosion, bent pins, or cross-contamination with adjacent power pins. Clean and repair as necessary.
5
Step 5: After repairs, clear codes, cycle the left rear door open and closed several times, and verify proper door ajar warning operation and that 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 a short to battery voltage in the left rear door ajar switch circuit. The BCM is receiving constant battery voltage on the circuit when it should see a ground signal (door closed) or an open circuit (door open). This causes the vehicle t...
The most common cause of B1573 (Door Ajar LR Circuit Short To Battery) is: Damaged or chafed wiring harness in door jamb or hinge area causing short to B+ voltage
Typical repair costs for B1573 range from $75 to $400, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Safe to drive with no direct safety concerns. However, constant interior light drain may deplete battery, and security system may not arm properly. Repair at earliest convenience to prevent battery discharge and ensure proper vehicle security functions.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to B1573 to identify the root cause.
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Quick Info
Category
Body
System
Body Control System
Difficulty
Type
Manufacturer
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