P0172 on Toyota Corolla E140: System Too Rich (Bank 1)
Short answer: P0172 means “System Too Rich (Bank 1)”. The car’s computer has found a fault in the Engine system and turns on the Check engine light (MIL). First check: read the code and freeze-frame data with an OBD-II scanner.
Standard OBD-II code Same meaning on all cars (SAE J2012). Not checked against this car’s factory manual.
- Code
- P0172
- System
- Engine
- Dashboard light
- Check engine light (MIL)
- Applies to
- Generic OBD-II meaning. Not every code is used by this car.
- Confidence
- medium (generic OBD-II definition, not checked against the factory manual for this car)
- Source
- obd-codes.com
Symptoms and when it is set
- Check engine light on
- You will more than likely not notice any drivability problems, although there
- May be symptoms such as a misfire
Likely causes
- The MAF (Mass Air Flow) Sensor is dirty or faulty. Note: The use of "oiled"
- Air filters can cause the MAF to become dirty if the filter is over-oiled
- There is also an issue with some vehicles where the MAF sensors leak the silicone
- Potting material used to protect the circuitry
- There could be a vacuum leak
- There could be a fuel pressure or delivery problem
What to check, in order
- Read the code and freeze-frame data with an OBD-II scanner
- Check the connector and wiring of the part named in the code
- Test the part with scanner live data or a multimeter, using the values in the repair manual
- Fix the cause, clear the code and test-drive
Related on this car
Same code on other cars
- P0172 · Toyota Passo (1st gen)
- P0172 · Toyota Corolla (9th gen, E120)
- P0172 · Toyota Corolla (11th gen, E170)
- P0172 · Honda City (5th gen, GM2)
- P0172 · Honda Civic (10th gen, FC)
- P0172 · Suzuki Wagon R (Pakistan, K10B)
- P0172 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.