P0172 · blink 26 – SYSTEM TOO RICH(FUEL TRIM)

System: EFI 1NZ-FE/2NZ-FE
Dashboard light: Malfunction indicator lamp (Check Engine)
Check-engine blink code: 26
Market note: HONG KONG ONLY
Applies to: 2NZ-FE 1.3 (PK XLi/GLi NZE120) and 1NZ-FE 1.5 (JDM NZE121/NZE124 Corolla/Fielder/Runx)
Description: SYSTEM TOO RICH(FUEL TRIM)
Detection / symptoms: Detection: Oxygen sensor voltage is 0.45 V or less (lean) for 90 sec. under conditions (a), (b) and (c): (2 trip detection logic) (a) Water temp.: 70˚C (158˚F) or more (b) Engine speed: 1,500 rpm or more (c) Vehicle speed: 100 km/h (62 mph) or less
Possible causes: Air intake (hose loose); Fuel line pressure; Open or short in oxygen sensor circuit; Oxygen sensor malfunction; Air flow meter; Water temp. sensor; Gas leakage on exhaust system
What to check: Workshop check order (RM821E): CHECK EMISSION CONTROL SYSTEM -> CHECK FUEL INJECTOR ASSY -> CHECK WATER TEMPERATURE SENSOR -> CHECK FOR SPARK AND IGNITION -> CHECK FUEL PRESSURE -> CHECK EXHAUST GAS LEAKAGE POINT -> READ VALUE OF O2S B1,S1 -> CHECK HARNESS AND CONNECTOR(ENGINE ECU−OXYGEN SENSOR) (See -> PERFORM CONFIRMATION DRIVING PATTERN -> READ OUTPUT DTC CODES
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