P0135 · blink 21 – OXYGEN SENSOR HEATER CIRCUIT MALFUNCTION(BANK1 SENSOR1)

System: EFI 1NZ-FE/2NZ-FE
Dashboard light: Malfunction indicator lamp (Check Engine)
Check-engine blink code: 21
Market note: UNLEADED GASOLINE ONLY
Applies to: 2NZ-FE 1.3 (PK XLi/GLi NZE120) and 1NZ-FE 1.5 (JDM NZE121/NZE124 Corolla/Fielder/Runx)
Description: OXYGEN SENSOR HEATER CIRCUIT MALFUNCTION(BANK1 SENSOR1)
Detection / symptoms: Detection: S When the heater operates, heater current exceeds 2 A (2 trip detection logic) S Heater current of 0.2 A or less when the heater operates (2 trip detection logic)
Possible causes: Open or short in heater circuit of oxygen sensor; Oxygen sensor heater; Engine ECU
What to check: See RM page (inspection steps not parsed)
Confidence: high (official Toyota RM821E)

From the factory service material. Clear the code and test-drive to confirm it returns. Search all fault codes · Common problems · Warning lights