CorollaFix

P0172 (blink 26, 3ZZ) on Toyota Corolla E120: SYSTEM TOO RICH(FUEL TRIM)

Short answer: P0172 means “SYSTEM TOO RICH(FUEL TRIM)”. The car’s computer has found a fault in the EFI 3ZZ-FE system and turns on the Malfunction indicator lamp (Check Engine). First check: workshop check order (RM821E): CHECK EMISSION CONTROL SYSTEM -> CHECK FUEL INJECTOR ASSY -> CHECK SENSOR, WATER TEMPERATURE -> 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) -> PERFORM CONFIRMATION DRIVING PATTERN -> READ OUTPUT DTC CODES.

Code
P0172 · blink 26
System
EFI 3ZZ-FE
Dashboard light
Malfunction indicator lamp (Check Engine)
Applies to
3ZZ-FE 1.6 (PK SE Saloon 1.6 2002-05 ZZE121)
Confidence
high (official Toyota RM821E)
Source
toyotamanuals.gitlab.io

Symptoms and when it is set

  1. 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

  1. 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, in order

  1. Workshop check order (RM821E): CHECK EMISSION CONTROL SYSTEM -> CHECK FUEL INJECTOR ASSY -> CHECK SENSOR, WATER TEMPERATURE -> 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) -> PERFORM CONFIRMATION DRIVING PATTERN -> READ OUTPUT DTC CODES

Related on this car

Same code on other cars

← P0171/25 P0325/52 →

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.