Check Engine Lamp Circuit
2010-2021 Fiat Uno 1.0L I4 Flex Fire Evo
Description
Malfunction in the check engine/MIL indicator lamp circuit in the instrument cluster.
Symptoms
- Check engine light does not illuminate during bulb check
- Light stays on with no DTC stored
- Light flickering
- Cannot determine if engine codes are present
Common Causes
- Burnt out MIL bulb/LED
- Cluster circuit board fault
- Wiring from PCM to cluster damaged
- PCM MIL driver failure
Diagnostic Steps
- Check bulb during key-on bulb check
- Test MIL drive circuit from PCM
- Inspect cluster wiring
- Scan PCM for codes
- Test cluster LED
Repair Notes
Replace MIL bulb/LED in cluster or repair wiring from PCM to cluster.
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
B0420 on Other Vehicles
Fiat 124 Spider
2017-2020 1.4L I4 Turbo
Fiat 126p Maluch
1973-2000 0.65L I2 Air-Cooled
Fiat 126p Maluch
1987-2000 0.7L I2 Air-Cooled
Fiat 500
2012-2019 1.4L I4
Fiat 500 Abarth
2012-2019 1.4L I4 Turbo
Fiat 500 BR
2011-2020 1.4L I4 Flex Fire Evo
Fiat 500 PL
2007-2025 1.0L I3 Hybrid FireFly 70
Fiat 500 PL
2007-2025 1.2L I4 Fire 69
Common Questions
What does code B0420 mean on a 2010-2021 Fiat Uno?
B0420 stands for "Check Engine Lamp Circuit". Malfunction in the check engine/MIL indicator lamp circuit in the instrument cluster.
What are the symptoms of B0420 on a Fiat Uno?
Common symptoms of B0420 include: Check engine light does not illuminate during bulb check, Light stays on with no DTC stored, Light flickering, Cannot determine if engine codes are present.
What causes B0420 on a 2010-2021 Fiat Uno?
Common causes of B0420 include: Burnt out MIL bulb/LED, Cluster circuit board fault, Wiring from PCM to cluster damaged, PCM MIL driver failure.