B121A Code: Meaning, Causes, and Symptoms | OBD2 Codes

B121A – Keypad Illumination Output Circuit Short to Ground

 

B121A Possible Symptoms

 

Engine Light ON (or Service Engine Soon Warning Light)

 

B121A Possible Causes

 

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

 

B121A Description

 

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.