What Does B2515 Mean?
B2515 indicates the body control module (BCM) has detected an electrical fault in the heater blower motor relay circuit. This code sets when the BCM commands the relay on or off but detects an abnormal voltage, current draw, or lack of feedback signal from the relay control circuit. The HVAC system's ability to circulate air through the cabin vents is directly affected, potentially resulting in no blower operation or blower stuck in one speed.
Common Causes
35%
Faulty heater blower motor relay with internal contact failure or coil resistance out of specification
30%
Damaged wiring harness or corroded connector between BCM and blower relay including chafed wires, broken conductors, or water intrusion
20%
Failed blower motor causing excessive current draw that damages relay contacts or triggers overcurrent protection
10%
BCM internal driver circuit failure preventing proper relay control signal output
5%
Blown fuse or fusible link in the blower motor relay power supply circuit
Diagnostic Steps
1
Step 1: Locate the heater blower motor relay in the power distribution center or relay box. Visually inspect the relay for burn marks, melted plastic, or corrosion on terminals. Check all related fuses for continuity using a test light or multimeter.
2
Step 2: Remove the blower relay and test it with a multimeter. Check coil resistance between control terminals (typically 70-120 ohms) and verify contact continuity when energized with a 12V power supply and ground. Listen for audible click when energized.
3
Step 3: With relay removed, use a multimeter to check for battery voltage at the relay power supply terminal and verify ground circuit continuity. Check the BCM control signal wire for voltage when commanded on (typically switches from 12V to ground or vice versa depending on design).
4
Step 4: Inspect the wiring harness between BCM and relay connector for damage, chafing, or corrosion. Perform voltage drop test on both power and ground circuits with blower motor operating under load (should be less than 0.5V).
5
Step 5: Disconnect the blower motor connector and measure motor resistance (typically 1-5 ohms) and check for shorts to ground or power. Command blower motor on via scan tool active test and monitor current draw at the relay (should be 5-25 amps depending on vehicle).
6
Step 6: If all components test good, suspect BCM internal relay driver failure. Verify BCM has proper power, ground, and communication on CAN bus. Clear codes, install known-good relay, and road test with scan tool monitoring relay command status versus actual feedback.
Estimated Repair Cost
$75 - $450
Parts + labor, varies by vehicle and location
B2515 indicates the body control module (BCM) has detected an electrical fault in the heater blower motor relay circuit. This code sets when the BCM commands the relay on or off but detects an abnormal voltage, current draw, or lack of feedback signal from the relay control circuit. The HVAC system'...
The most common cause of B2515 (Heater Blower Relay Circuit Failure) is: Faulty heater blower motor relay with internal contact failure or coil resistance out of specification
Typical repair costs for B2515 range from $75 to $450, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Vehicle is safe to drive with this fault. Primary concern is loss of cabin heating, defrosting, or air conditioning circulation which may impact windshield visibility in adverse weather conditions. Repair should be prioritized before winter or hot weather operation.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to B2515 to identify the root cause.
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Quick Info
Category
Body
System
HVAC Climate Control System
Difficulty
Type
Generic (SAE)
Recommended Tools
OBD2 Scanner
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