What Does B1500 Mean?
This code indicates the Body Control Module (BCM) has detected an open circuit in the left turn signal lamp circuit. An open circuit means there is a break in the electrical pathway preventing current flow to the left turn signal bulb(s). The BCM monitors the circuit for proper resistance and current draw, and sets this code when it detects infinite resistance or no current flow when the turn signal is activated.
Common Causes
45%
Burned out left turn signal bulb or faulty bulb socket with corrosion/poor contact
30%
Broken or disconnected wiring between BCM and left turn signal lamp assembly
15%
Corroded or loose connector at turn signal lamp assembly or BCM
10%
Failed Body Control Module output driver for left turn signal circuit
Diagnostic Steps
1
Step 1: Perform visual inspection of the left front and left rear turn signal bulbs. Remove bulbs and check for broken filament, blackened glass, or corrosion in the socket. Check for bent or damaged socket terminals. Replace bulb if defective and verify operation.
2
Step 2: If bulbs are good, inspect all connectors at the left turn signal lamp assemblies. Check for corrosion, moisture intrusion, pushed-back pins, or damaged terminals. Clean connectors with electrical contact cleaner and apply dielectric grease.
3
Step 3: Using a digital multimeter, check for battery voltage at the turn signal lamp socket while the left turn signal is activated. If no voltage present, trace wiring back toward the BCM checking for breaks, cuts, or damage. Pay attention to areas where wiring flexes (door jambs, body seams).
4
Step 4: Backprobe the BCM connector at the left turn signal output terminal. Check for continuity between the BCM output pin and the lamp socket with turn signal off (should show open circuit with bulb installed). With turn signal activated, check for voltage output from BCM (should show 12V pulsing).
5
Step 5: If BCM shows proper voltage output but no voltage at lamp, isolate the wiring fault by performing continuity test from BCM to lamp socket with harness disconnected at both ends. Repair or replace damaged wiring as needed.
6
Step 6: Clear codes and verify repair by operating left turn signal through multiple cycles. Confirm no codes return and proper flash rate is restored.
Estimated Repair Cost
$50 - $400
Parts + labor, varies by vehicle and location
This code indicates the Body Control Module (BCM) has detected an open circuit in the left turn signal lamp circuit. An open circuit means there is a break in the electrical pathway preventing current flow to the left turn signal bulb(s). The BCM monitors the circuit for proper resistance and curren...
The most common cause of B1500 (Lamp Turn Signal Left Circuit Open) is: Burned out left turn signal bulb or faulty bulb socket with corrosion/poor contact
Typical repair costs for B1500 range from $50 to $400, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Not safe to drive without functional turn signals as they are legally required and critical for communicating directional intent to other drivers. Repair immediately to prevent accidents and avoid traffic citations. Operating without working turn signals significantly increases collision risk.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to B1500 to identify the root cause.
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Quick Info
Category
Body
System
Exterior Lighting System
Difficulty
Type
Manufacturer
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