DTC C1020-00: Ignition Switch On/Start Position Malfunction [11/2021 - ]: Procedure
WARNING: This page is about a different car, the 2025 Lexus NX 350h, 2024 Lexus NX 350h, 2023 Lexus NX 350h, and 2022 Lexus NX 350h. However, it is still accessible from the selected car via links, so may be relevant.
- CHECK HARNESS AND CONNECTOR (IG1 TERMINAL)
- Make sure that there is no looseness at the locking part and the connecting part of the connector.
OK
The connector is securely connected.
- Disconnect the A39 No. 1 skid control ECU (brake booster with master cylinder assembly) connector.
- Check both the connector case and the terminals for deformation and corrosion.
OK
No deformation or corrosion.
- Turn the ignition switch to ON.
- Measure the voltage according to the value(s) in the table below.
Standard Voltage
Tester Connection Condition Specified Condition A39-31 (IG1) - Body ground Ignition switch ON 11 to 14 V Result
Result Proceed to 11 to 14 V. A Below 11 V. B
Result:
A
REPLACE BRAKE BOOSTER WITH MASTER CYLINDER ASSEMBLY. Refer to REMOVAL [11/2021 - ]
Result:
B
REPAIR OR REPLACE HARNESS OR CONNECTOR
- Make sure that there is no looseness at the locking part and the connecting part of the connector.