Fault on fluid reservoir level sensor F.
Low severity. Can I keep driving?You can normally keep driving. If it affects the lights or visibility, get it repaired before driving at night or in the rain.
This code affects a body system, such as the lights, doors, climate control, seats, or instrument cluster.
Symptoms
- Warning light or symbol related to the affected system
- Comfort or safety function impaired
Most likely causes
- Float or sensor failed
What to check, in order
Start with the simplest. You can tick off each step.
Good to know
- Repair difficulty: easy
What each character of B0121 means
- B: Body
- 0: Generic code: same on every make
- 1: Subsystem depends on the code range
- 21: Specific fault in that system
Frequently asked questions
Can I keep driving with code B0121?
You can normally keep driving. If it affects the lights or visibility, get it repaired before driving at night or in the rain.
What causes code B0121?
The most common causes are: float or sensor failed.
Related codes
- B011FFluid Reservoir Level Sensor D
- B011EFluid Reservoir Level Sensor C
- B011DFluid Reservoir Level Sensor B
- B011CFluid Reservoir Level Sensor A
Sources
Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.