TPMS Sensor Frequency Mismatch
2021-2021 Audi A4 2.0L I4 TFSI
The 2021 Audi A4 is equipped with a 2.0L inline-4 turbocharged gasoline engine. Below you'll find detailed b1021 diagnostic code information including labor time estimates, cost ranges, and technician notes specific to this engine configuration.
Description
One or more TPMS sensors are transmitting on a different frequency than the vehicle receiver expects.
Symptoms
- TPMS warning light on
- Some sensors not reading
- New sensor not recognized
Common Causes
- Aftermarket sensor with wrong frequency
- European/Asian frequency sensor on US vehicle
- Mixed sensor brands
- Incorrect replacement sensor part number
Diagnostic Steps
- Verify sensor frequency with TPMS tool
- Check sensor part number compatibility
- Compare sensor frequency to vehicle specification
- Test each sensor individually
Repair Notes
Replace mismatched sensors with correct frequency sensors. US vehicles typically use 315 MHz, European/Asian use 433 MHz.
Related Codes
Other Body Codes
- B0001Driver Frontal Stage 1 Deployment Control
- B0002Driver Frontal Stage 2 Deployment Control
- B0003Passenger Frontal Stage 1 Deployment Control
- B0004Passenger Frontal Stage 2 Deployment Control
- B0005Driver Knee Airbag Deployment Circuit
- B0006Passenger Knee Airbag Deployment Circuit
- B0007Rear Left Side Airbag Deployment Circuit
- B0008Rear Right Side Airbag Deployment Circuit
- B0009Rear Center Airbag Deployment Circuit
- B0010Driver Side Airbag Deployment
B1021 on Other Vehicles
Common Questions
What does code B1021 mean on a 2021-2021 Audi A4?
B1021 stands for "TPMS Sensor Frequency Mismatch". One or more TPMS sensors are transmitting on a different frequency than the vehicle receiver expects.
What are the symptoms of B1021 on a Audi A4?
Common symptoms of B1021 include: TPMS warning light on, Some sensors not reading, New sensor not recognized.
What causes B1021 on a 2021-2021 Audi A4?
Common causes of B1021 include: Aftermarket sensor with wrong frequency, European/Asian frequency sensor on US vehicle, Mixed sensor brands, Incorrect replacement sensor part number.
Last updated: March 2026