Engine-Codes - Mercury - B121A Mercury

B121A Mercury Code - Keypad Illumination Output Circuit Short to Ground

- Code Popularity: 1,070 Views
- Repair Importance Level: 3/3
- Repair Difficulty Level: 3/3
Table of contents

|What are the Possible Causes of the Code B121A Mercury?

  • Faulty Keyless Entry Keypad
  • Keyless Entry Keypad harness is open or shorted
  • Keyless Entry Keypad circuit poor electrical connection
  • Faulty Body Control Module (BCM)

|How to Fix the B121A 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.

|What is the Cost to Diagnose the Code B121A Mercury?

Labor: 1.0

The cost to diagnose the B121A 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.

Does your car have Safety Recalls? → Check here

|What are Code B121A Mercury Possible Symptoms?

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

|What Does the B121A Mercury Code Mean?

The keypad feature operates independently of key position status, vehicle speed, or transmission position. When a keypad button is touched, the keypad buttons illuminate to provide better visibility. The keypad is also illuminated any time that the courtesy lighting is on. If the lock all doors command is entered or 5 seconds have elapsed since the last button press, the illumination is turned off.
Each vehicle equipped with a keypad is programmed with a 5-digit entry code. This code is provided to the customer through a wallet card in the Owner's Literature. In addition, this code is available through a scan tool and is also printed on the BCM label. When entering codes each digit must be entered within 5 seconds of the previous button press.
When any keypad button is pressed the Body Control Module (BCM) sends voltage to the keyless entry keypad LEDs on the illumination circuit to assist the driver in entering an access code at night. The keyless entry keypad has a separate ground circuit for the LEDs. A Diagnostic Trouble Code (DTC) that sets when the BCM detects a short to ground on the keyless entry keypad illumination circuit.

Keypad Illumination Output Circuit Short to Ground

|Need more Information on the B121A Mercury Code?

Need more information on how to fix the B121A Mercury code? Get Access to Factory Service Manuals

|Need Help with the B121A Mercury Code?

Get the B121A Mercury code diagnosed by a professional: Find a repair shop in your area