What Does B2560 Mean?
This code indicates the Body Control Module (BCM) or HVAC control module has detected a short to ground in the auxiliary air conditioning blower motor relay control circuit. The control module detected current flow to ground when commanding the relay, indicating an unintended electrical path between the relay control circuit and vehicle ground. This prevents proper operation of the auxiliary rear or second zone A/C blower motor system.
Common Causes
40%
Damaged, chafed, or pinched wiring harness causing the relay control circuit to short against vehicle chassis or ground
30%
Failed auxiliary A/C blower motor relay with internal short to ground in coil or control circuit
20%
Corroded or water-damaged relay socket/connector causing short circuit path to ground
10%
Failed BCM or HVAC control module with internal driver circuit shorted to ground
Diagnostic Steps
1
Step 1: Perform visual inspection of auxiliary blower motor relay location, typically in underhood or auxiliary fuse box. Check for water intrusion, corrosion, burnt terminals, or melted components. Remove relay and inspect socket for damage.
2
Step 2: With relay removed and ignition off, use digital multimeter to measure resistance between relay control terminal pin at socket and known good chassis ground. Reading should be infinite (open circuit); any continuity indicates short to ground in wiring or module.
3
Step 3: Disconnect BCM/HVAC control module connector. Re-measure resistance from relay control circuit to ground. If short disappears (infinite resistance), module has failed internal driver. If short persists, harness is shorted to ground between relay and module.
4
Step 4: If harness short is confirmed, trace wiring from relay socket to control module, inspecting for pinch points, chafing against metal, damaged insulation especially near sharp edges, hinges, or mounting brackets. Use wiring diagram to identify circuit color and routing.
5
Step 5: Install known-good relay and repair any wiring damage. Clear codes and command auxiliary blower motor operation using scan tool bidirectional controls while monitoring relay operation and current draw to verify proper function.
6
Step 6: Road test vehicle with auxiliary A/C system operating, monitor for code recurrence and verify auxiliary blower motor functions properly at all speed settings.
Estimated Repair Cost
$100 - $600
Parts + labor, varies by vehicle and location
This code indicates the Body Control Module (BCM) or HVAC control module has detected a short to ground in the auxiliary air conditioning blower motor relay control circuit. The control module detected current flow to ground when commanding the relay, indicating an unintended electrical path between...
The most common cause of B2560 (Aux A/C Blower Motor Relay Circuit Short to Ground) is: Damaged, chafed, or pinched wiring harness causing the relay control circuit to short against vehicle chassis or ground
Typical repair costs for B2560 range from $100 to $600, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Safe to continue driving. This affects only the auxiliary or rear A/C blower motor operation and does not impact vehicle safety or primary HVAC function. Repair at convenience, though passengers in rear seating areas will have no climate control.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to B2560 to identify the root cause.
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Quick Info
Category
Body
System
Auxiliary HVAC System
Difficulty
Type
Generic (SAE)
Recommended Tools
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