Engine-Codes - Generic - B121D

B121D Code - Rear HVAC Mode Control Input Circuit Short

- Code Popularity: 2,846 Views
- Repair Importance Level: 3/3
- Repair Difficulty Level: 3/3
Table of contents

|What are the Possible Causes of the Code B121D?

  • 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 to Fix the B121D Code?

Start by checking 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.

|Code 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

|What is the Cost to Diagnose the Code B121D?

Labor: 1.0

The cost to diagnose the B121D code is 1.0 hour of labor. The auto repair's diagnosis time and labor rates vary by location, vehicle's make and model, and even your engine type. Most auto repair shops charge between $75 and $150 per hour.

Does your car have Safety Recalls? → Check here

|What are Code B121D Possible Symptoms?

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

|What Does the B121D Code Mean?

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.

Rear HVAC Mode Control Input Circuit Short

|Need more Information on the B121D Code?

Need more information on how to fix the B121D code? Get Access to Factory Service Manuals

|Code B121D Information for Specific Makes

|Need Help with the B121D Code?

Get the B121D code diagnosed by a professional: Find a repair shop in your area