What Does B2564 Mean?
This code indicates that the Body Control Module (BCM) or HVAC control module has detected a short to ground in the auxiliary air conditioning blower motor speed 2 circuit. This fault specifically affects the second speed setting of the rear or auxiliary A/C blower motor system, commonly found in larger vehicles with separate rear climate controls. The control module detected abnormally low resistance or voltage on the blower speed control circuit, indicating current is flowing directly to ground instead of through the intended load.
Common Causes
45%
Damaged or chafed wiring harness causing wire insulation breakdown and direct contact with vehicle chassis or ground
30%
Failed auxiliary blower motor with internal short circuit to its housing/ground
15%
Faulty blower motor speed control resistor or power module with internal short to ground
10%
Corroded or moisture-damaged electrical connectors at blower motor or control module causing unintended ground paths
Diagnostic Steps
1
Step 1: Perform visual inspection of auxiliary blower motor wiring harness from control module to blower motor, looking for damaged insulation, burned wires, chafing points against metal chassis, or signs of moisture intrusion at connectors
2
Step 2: Disconnect the auxiliary blower motor connector and use a digital multimeter to measure resistance from the speed 2 control wire terminal (at the harness side) to chassis ground with ignition off; reading should be greater than 10k ohms (open circuit). A low resistance reading (under 5 ohms) confirms short to ground in wiring
3
Step 3: If wiring tests normal, measure resistance across the blower motor terminals with motor disconnected; normal readings vary by motor but typically 2-20 ohms. Then check resistance from each motor terminal to motor housing/ground; should be infinite (open). Low resistance to ground indicates failed motor
4
Step 4: Inspect and test the blower motor resistor/power module by disconnecting it and checking for physical damage, burned components, or corrosion. Measure resistance from speed 2 output terminal to ground with module disconnected; should be open circuit
5
Step 5: After repairing identified fault (replace damaged wiring, motor, or resistor), clear codes, reconnect all components, and activate auxiliary A/C blower through all speed settings to verify proper operation and confirm code does not return
Estimated Repair Cost
$150 - $650
Parts + labor, varies by vehicle and location
This code indicates that the Body Control Module (BCM) or HVAC control module has detected a short to ground in the auxiliary air conditioning blower motor speed 2 circuit. This fault specifically affects the second speed setting of the rear or auxiliary A/C blower motor system, commonly found in la...
The most common cause of B2564 (Aux A/C Blower Speed 2 Circuit Short to Ground) is: Damaged or chafed wiring harness causing wire insulation breakdown and direct contact with vehicle chassis or ground
Typical repair costs for B2564 range from $150 to $650, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Vehicle is safe to drive as this only affects auxiliary rear climate control comfort features and does not impact vehicle operation or primary safety systems. Repair can be scheduled at convenience, though passengers in rear seating area will have reduced or no auxiliary air conditioning functionality.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to B2564 to identify the root cause.
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Quick Info
Category
Body
System
HVAC System (Auxiliary Climate Control)
Difficulty
Type
Generic (SAE)
Recommended Tools
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