P121A – BMW DTC

BMW DTC P121A – Brake Booster Pump Control Circuit/Open

DTC P121A meaning on BMW

The DTC P121A error code on a BMW indicates an issue with the brake booster pump control circuit being open. This means that there is a malfunction in the circuit that controls the brake booster pump, which can affect the vehicle’s braking system.

BMW DTC P121A symptoms

Some common symptoms associated with the BMW DTC P121A error code include:

• Illuminated brake warning light on the dashboard
• Decreased brake assist functionality
• Increased brake pedal effort required to stop the vehicle

BMW DTC P121A causes

The DTC P121A error code on a BMW can be caused by various factors, including:

• Faulty brake booster pump control module
• Damaged wiring or connectors in the brake booster pump circuit
• Low brake fluid level

BMW DTC P121A seriousness

The DTC P121A error code should be addressed promptly as it can impact the vehicle’s braking performance and safety. Driving with a malfunctioning brake booster pump control circuit can lead to compromised braking ability, increasing the risk of accidents.

How to diagnose DTC P121A on BMW

To diagnose the DTC P121A error code on a BMW, you can perform the following steps:

1. Use a diagnostic scanner to retrieve the fault codes stored in the vehicle’s computer
2. Inspect the brake booster pump control module for any visible damage
3. Check the wiring and connectors in the brake booster pump circuit for continuity and proper connection
4. Verify the brake fluid level in the reservoir

How to fix DTC P121A on BMW

To fix the DTC P121A error code on a BMW, you may need to:

1. Replace the faulty brake booster pump control module
2. Repair or replace damaged wiring or connectors in the brake booster pump circuit
3. Top up the brake fluid to the recommended level

How to erase DTC P121A on BMW

To erase the DTC P121A error code on a BMW, you can:

1. Use a diagnostic scanner to clear the fault codes stored in the vehicle’s computer
2. After fixing the underlying issue causing the error code, perform a test drive to ensure the problem is resolved

Recommended tools & DTC Scanners for BMW

Best Diagnostic App for modern BMWs: BimmerLink

Recommended Bluetooth adapter for Bimmerlink: OBDLink CX

Cable adapter for Bimmerlink: Enet Cable USB Type C

For older BMWs we recommend: Autel AutoLink AL319 (2024 version)

Easy-to-use Multimeter for reliable diagnostics: AstroAI Auto-ranging Multimeter

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