A/C Request B Circuit
General electrical fault on the second A/C request input B. Many vehicles have two HVAC zones, a rear evaporator request, or a redundant request line — input B carries that signal. With the input invalid, the ECM cannot honour zone B compressor demand or rear-evap operation.
Affected components
- Ac request input b
Common causes
- High likelihood: Open or shorted A/C request wire B
- Medium likelihood: HVAC module not transmitting request B
Diagnostic notes
- The malfunction indicator lamp may illuminate
Related codes
Sources
Diagnostic information is provided for reference only. Confirm the code with a compatible scan tool and follow the vehicle manufacturer's service procedures before replacing components.