What Does B1338 Mean?
This code indicates the Body Control Module (BCM) has detected a short to ground in the rear right (RR) door ajar switch circuit. The BCM monitors door ajar switches to determine if doors are open or closed for interior lighting, security systems, and driver information displays. A short to ground causes the circuit voltage to drop below the expected threshold, making the BCM incorrectly register the door as constantly open.
Common Causes
45%
Damaged or chafed wiring harness between the door jamb and body, commonly worn from repeated door opening/closing
30%
Faulty rear right door ajar switch with internal short to ground or corroded terminals
15%
Water intrusion or corrosion at door ajar switch connector causing short circuit
10%
BCM internal circuit fault or damaged BCM connector pin
Diagnostic Steps
1
Step 1: Visually inspect the rear right door jamb wiring harness for chafing, pinching, or exposed wires, especially in the rubber boot between door and body. Check for signs of wire damage or worn insulation contacting metal surfaces.
2
Step 2: Disconnect the rear right door ajar switch connector and use a digital multimeter to measure resistance between the switch signal wire and ground. Reading should be infinite ohms (open circuit). If continuity exists, wiring is shorted to ground.
3
Step 3: With switch connector still disconnected, check for continuity between the BCM side of the harness signal wire and ground. If continuity exists, trace and repair the shorted wire in the harness. If no continuity, suspect the door ajar switch itself.
4
Step 4: Inspect door ajar switch connector for corrosion, moisture, or bent pins. Clean connector with electrical contact cleaner and dielectric grease if needed.
5
Step 5: Test the door ajar switch by measuring resistance across its terminals while manually actuating the switch. Should show open circuit when door is closed, closed circuit when open. Replace if faulty or showing continuity to ground.
6
Step 6: After repairs, clear codes, cycle the rear right door open and closed multiple times, and verify the BCM correctly detects door status without code returning.
Estimated Repair Cost
$75 - $350
Parts + labor, varies by vehicle and location
This code indicates the Body Control Module (BCM) has detected a short to ground in the rear right (RR) door ajar switch circuit. The BCM monitors door ajar switches to determine if doors are open or closed for interior lighting, security systems, and driver information displays. A short to ground c...
The most common cause of B1338 (Door Ajar RR Circuit Short To Ground) is: Damaged or chafed wiring harness between the door jamb and body, commonly worn from repeated door opening/closing
Typical repair costs for B1338 range from $75 to $350, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Safe to continue driving. This code primarily affects interior lighting operation and may prevent proper door open warnings or security system arming. Repair at convenience, though prolonged interior light activation could drain the battery.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to B1338 to identify the root cause.
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Quick Info
Category
Body
System
Body Control and Lighting System
Difficulty
Type
Manufacturer
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