P0171 (blink 25) on Toyota Corolla E120: SYSTEM TOO LEAN(FUEL TRIM)
Short answer: P0171 means “SYSTEM TOO LEAN(FUEL TRIM)”. The car’s computer has found a fault in the EFI 1NZ-FE/2NZ-FE system and turns on the Malfunction indicator lamp (Check Engine). First check: 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.
- Code
- P0171 · blink 25
- System
- EFI 1NZ-FE/2NZ-FE
- Dashboard light
- Malfunction indicator lamp (Check Engine)
- Applies to
- 2NZ-FE 1.3 (PK XLi/GLi NZE120) and 1NZ-FE 1.5 (JDM NZE121/NZE124 Corolla/Fielder/Runx)
- Market note
- HONG KONG ONLY
- Confidence
- high (official Toyota RM821E)
- Source
- toyotamanuals.gitlab.io
Symptoms and when it is set
- 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
Likely 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
Related on this car
- Intake manifold gasket vacuum leak (1ZZ)
- Dirty MAF sensor
- Poor fuel average after a bad tune-up
- All fault codes for this car
- Warning lights
- Where the parts are (parts map)
- Common problems
Same code on other cars
- P0171 · Toyota Passo (1st gen)
- P0171 · Toyota Vitz (1st gen)
- P0171 · Toyota Corolla (11th gen, E170)
- P0171 · Toyota Corolla (10th gen, E140)
- P0171 · Honda City (5th gen, GM2)
- P0171 · Honda Civic (10th gen, FC)
- P0171 · Suzuki Wagon R (Pakistan, K10B)
- P0171 on all cars compared
Clearing the code does not fix the fault. If it comes back, the problem is still there. For brakes, airbags and steering, see a trained mechanic.