B121D - Rear HVAC Mode Control Input Circuit Short

Repair Importance Level: 3/3
Repair Difficulty Level: 3/3  What does this mean?

B121D Possible Causes

  • Faulty Rear HVAC Mode Control
  • Rear HVAC Mode Control harness is open or shorted
  • Rear HVAC Mode Control circuit poor electrical connection
  • Faulty Heating, Ventilation, and Air-Conditioning (HVAC) Module

How do I fix code B121D

    Check the "Possible Causes" listed above. Visually inspect the related wiring harness and connectors. Check for damaged components and look for broken, bent, pushed out, or corroded connector's pins.

B121D Tech Notes

B121D:11 Rear HVAC Mode Control Input Circuit Short to Ground
B121D:15 Rear HVAC Mode Control Input Circuit Short to Battery or Open

Cost of diagnosing the B121D code

    Labor: 1.0

    The cost of diagnosing the B121D code is 1.0 hour of labor. The auto repair labor rates vary widely across the country, and even within the same city. Most auto repairs shops charge between $75 and $150 per hour.

B121D Possible Symptoms

  • Engine Light ON (or Service Engine Soon Warning Light)

B121D Meaning

Under normal operation, the rear auxiliary control is supplied a 5-volt reference and ground from the Heating, Ventilation, and Air-Conditioning (HVAC) Module. When the auxiliary blower motor speed, airflow mode or temperature control is adjusted, the HVAC module reads the voltage from the rear auxiliary climate controls on the auxiliary blower motor speed, airflow mode, and temperature control feedback circuits to determine the requested setting. The OBDII code sets when the HVAC module senses an open, or short to ground or voltage on the rear auxiliary climate controls temperature input circuit.
OBDII Code B121D - Rear HVAC Mode Control Input Circuit Short - Engine-Codes.com

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