What Does B2580 Mean?
This code indicates the Body Control Module (BCM) has detected a malfunction in the auxiliary blower sense switch circuit. This circuit monitors the status of the auxiliary climate control blower motor switch, which controls a secondary or rear HVAC blower system. The BCM has identified an abnormal voltage reading, open circuit, short circuit, or lack of expected signal from the sense switch that monitors blower operation.
Common Causes
35%
Faulty auxiliary blower motor sense switch or integrated sensor within the blower assembly
30%
Damaged, corroded, or loose wiring and connectors in the auxiliary blower sense circuit between BCM and blower switch
20%
Failed auxiliary blower motor causing abnormal current draw affecting sense circuit feedback
15%
Body Control Module (BCM) internal circuit fault or software corruption
Diagnostic Steps
1
Step 1: Perform visual inspection of auxiliary blower motor assembly, sense switch connector, and associated wiring harness for physical damage, corrosion, water intrusion, burned terminals, or disconnected plugs. Check for proper connector seating.
2
Step 2: Using a digital multimeter, backprobe the sense switch connector with ignition on and measure voltage at the signal wire (typically 5V or 12V reference from BCM). Compare to manufacturer specifications for expected voltage range (usually 4.5-5.5V or 11-14V depending on system design).
3
Step 3: Test auxiliary blower motor operation directly by applying battery voltage and ground to motor terminals to verify motor functionality. Measure current draw with ammeter during operation and compare to specifications (typically 3-15 amps depending on speed setting).
4
Step 4: Check continuity between sense switch and BCM connector using multimeter with ignition off and connectors disconnected. Resistance should be less than 5 ohms for good circuit. Check for shorts to ground or power (should read infinite resistance).
5
Step 5: If all wiring and components test within specification, perform BCM monitoring with advanced scan tool while cycling auxiliary blower through all speed settings. Observe sense switch signal voltage in live data to identify intermittent faults or BCM processing issues.
6
Step 6: Clear code, operate auxiliary blower system through complete operational cycle, and rescan for code return. If code returns immediately with known-good components and wiring, suspect BCM internal fault requiring module replacement or reprogramming.
Estimated Repair Cost
$150 - $650
Parts + labor, varies by vehicle and location
This code indicates the Body Control Module (BCM) has detected a malfunction in the auxiliary blower sense switch circuit. This circuit monitors the status of the auxiliary climate control blower motor switch, which controls a secondary or rear HVAC blower system. The BCM has identified an abnormal ...
The most common cause of B2580 (Aux Blower Sense Switch Circuit Failure) is: Faulty auxiliary blower motor sense switch or integrated sensor within the blower assembly
Typical repair costs for B2580 range from $150 to $650, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Safe to continue driving as this only affects auxiliary climate control functionality. Rear or auxiliary passenger area heating/cooling will be compromised, but primary HVAC system and vehicle operation remain unaffected. Repair at convenience unless extreme weather conditions require full climate control capability.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to B2580 to identify the root cause.
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Quick Info
Category
Body
System
Climate Control System (HVAC)
Difficulty
Type
Generic (SAE)
Recommended Tools
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