What is the Toyota P0172 System Too Rich Fault?
2 Answers
Fault Code: P0712 Chinese Meaning: Transmission Fluid Temperature Sensor A Circuit Low Detailed Meaning: 1. Transmission Fluid Temperature (TFT) Sensor. The Transmission Fluid Temperature (TFT) sensor transmits the transmission fluid temperature as an electrical signal to the Electronic Control Unit (ECU) based on the principle of a thermistor. Its main function is to downshift and reduce speed when the temperature is too high. 2. Transmission Control Module (TCU). For some newer vehicles, the TCU uses this temperature signal to determine the viscosity of the transmission fluid, thereby adjusting line pressure and solenoid valve pressure. 3. Electronic Control Unit (ECU). When the Electronic Control Unit (ECU) detects that the signal voltage from the Transmission Fluid Temperature (TFT) sensor is continuously below the calibrated minimum value (temperature above 157 degrees Celsius), this fault code will appear.
Last time my car's check engine light came on, and it showed a P0172 code, which was really annoying. This indicates a rich fuel system condition, meaning there's unburned gasoline in the engine's cylinder head, and the exhaust has as little oxygen as if it's not breathing. There are many common causes: a faulty oxygen sensor is the most likely to give false signals; leaking or clogged fuel injectors that keep spraying; a dirty mass air flow sensor giving low readings that make the ECU inject more fuel; a malfunctioning fuel pressure regulator causing high pressure and excessive fuel delivery; or a vacuum leak introducing more air but sending wrong signals. This can lead to unstable idling, severe shaking, a sudden increase in fuel consumption by 1-2 liters, and black smoke causing heavy pollution. I tried clearing the fault code myself, but it quickly came back. It's best to go to a professional shop to read the data stream and check the short-term fuel trim values. They can replace sensors or adjust the fuel injection system. If left untreated, the catalytic converter could fail, costing over two thousand to repair.
