B0420moderate severityBody
Check Engine Lamp Circuit
on 2017 Toyota Highlander 3.5L V6 · AWD
What this code means
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.
Other Body codes on this vehicle
B0001
Driver Frontal Stage 1 Deployment Control
B0002
Driver Frontal Stage 2 Deployment Control
B0003
Passenger Frontal Stage 1 Deployment Control
B0004
Passenger Frontal Stage 2 Deployment Control
B0005
Driver Knee Airbag Deployment Circuit
B0006
Passenger Knee Airbag Deployment Circuit
B0007
Rear Left Side Airbag Deployment Circuit
B0008
Rear Right Side Airbag Deployment Circuit
B0009
Rear Center Airbag Deployment Circuit
B0010
Driver Side Airbag Deployment