Engine-Codes - Mercury - B121D MERCURY

B121D MERCURY Code - Rear HVAC Mode Control Input Circuit Short

- Code Popularity: 2,165 Views
- Repair Importance Level: 3/3
- Repair Difficulty Level: 3/3
Table of contents

|What are the Possible Causes of the B121D MERCURY Code?

  • 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 MERCURY 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.

|B121D MERCURY code 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 B121D MERCURY code?

Labor: 1.0

The cost to diagnose the B121D MERCURY 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.

|What are B121D MERCURY code possible symptoms?

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

|What Does the B121D MERCURY 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

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