BodyB121A
CautionSeverity: Caution - get it checked when you can
Keypad Illumination Output
Key terms: Control module: a small computer that runs one part of the car
1What it means in plain English
A body system has a fault. Depending on the make, this range can include airbags and seat belts, windows, locks and climate control, and also charging, brake, oil or coolant sensors.
2Common causes
- Wiring or connector fault
- Faulty sensor or switch
- Water or corrosion in a connector
- Control module fault
- Low battery voltage
3Can I drive?
Do not assume this code is safe to drive. If it concerns the brakes, brake vacuum, charging/alternator, engine oil or coolant, have it diagnosed before driving. Airbags or seat belts may not work in a crash, and a brake or charging fault can leave the car unsafe or stranded. For convenience systems (windows, locks, climate), have it checked when convenient.
This page gives general information. It is not professional advice. For a definite diagnosis and a repair quote, ask a qualified mechanic to inspect the car.
4Brand data 16
| Brand | Code | Description | System |
|---|---|---|---|
| Mercedes-Benz | B121A | No description available | Body |
| BYD | B121A | IGBT 1 drive function failure Brand | Body |
| Daewoo | B121A | No description available | Body |
| DFFS | B121A | Electric vehicle system main status and turn indicator status information is lost Brand | Body |
| Geely | B121A | Front Row Left Side Side Airbag Igniter Connecting to Battery Brand | Body |
| GM | B121A | No description available | Body |
| Holden | B121A | Left Front Fog Lamp Circuit Brand | Body |
| Honda | B121A | No description available | Body |
| Land Rover | B121A | Keypad Illumination Output Brand | Body |
| Mitsubishi | B121A | No description available | Body |
| Opel | B121A | No description available | Body |
| Peugeot | B121A | No description available | Body |
| Proton | B121A | No description available | Body |
| Saab | B121A | No description available | Body |
| Smart | B121A | No description available | Body |
| Suzuki | B121A | No description available | Body |
Legend: SAE is the generic J2012 description; Brand is text taken from that manufacturer’s data. Manufacturer rows keep the wording and language of the source data, and non-English text is tagged so screen readers pronounce it correctly.
5Extended variant codes 5
These 7-character codes are manufacturer-specific variants of B121A and may be reported by some scan tools.
| Brand | Code | Description | System |
|---|---|---|---|
| Mahindra | B121A00 | ECU Locked Due To Pretensioner Deployment Brand | Body |
| Mercedes-Benz | B121A07 | Electrical expansion valve 'Heat exchanger for cooling the high-voltage battery' has a malfunction. There is a mechanical fault. Brand | Body |
| Mercedes-Benz | B121A49 | Electrical expansion valve 'Heat exchanger for cooling the high-voltage battery' has a malfunction. There is an internal electrical fault. Brand | Body |
| Mercedes-Benz | B121A87 | Electrical expansion valve 'Heat exchanger for cooling the high-voltage battery' has a malfunction. The message is missing. Brand | Body |
| Mercedes-Benz | B121A98 | Electrical expansion valve 'Heat exchanger for cooling the high-voltage battery' has a malfunction. The component or the system has overtemperature. Brand | Body |
6Related codes
Browse Bxxx codes or B121xx codes.