QuestionI'm getting DTC codes p0171 p0172 p1471 p1453. I was been getting the p0171 p0172 p1471 codes I have replaced the o2 sensors and cleaned the maf. The p1453 is new. Do you know what could be causing them?
AnswerHi Shane,
too rich then too lean...sounds more like sensor control trouble.
Could be the IAT (intake air temperature):
The IAT sensor provides a signal that enables the ECM to adjust ignition timing and fuelling quantity according to the intake air temperature, thus ensuring optimum performance, driveability and emissions.
The IAT sensor is a Negative Temperature Coefficient (NTC) thermistor located in a plastic housing installed in the intake duct between the MAF sensor and the throttle body. The sensor is a push fit in the housing and sealed by an 'O' ring. A clip is integrated into the sensor to secure it in the housing.
If the input from the IAT sensor fails, the vehicle will continue to run. The ECM will substitute a default value using the information from the speed/load map to run the engine, but adaptive fuelling will be disabled.
Could also be the ECT (engine coolant temperature):
The ECT sensor provides the ECM with a signal voltage that varies with coolant temperature, to enable the ECM to adapt the fuelling quantity and ignition timing with changes of engine temperature.
The ECT sensor is located between the cylinder banks, between cylinders 3 and 6.
The ECT sensor consists of an encapsulated Negative Temperature Coefficient (NTC) thermistor which is in contact with the engine coolant. As the coolant temperature increases the resistance across the sensor decreases and as the coolant temperature decreases the sensor resistance increases. To determine the coolant temperature, the ECM supplies the sensor with a regulated 5 volts power supply and monitors the return signal voltage. The ECM also outputs the coolant temperature on the CAN system, to operate the coolant temperature gauge.
If the ECT signal is missing, or outside the acceptable range, the ECM assumes a default temperature reflecting a part warm engine condition. This enables the engine to function, but with reduced driveability when cold and increased emissions, resulting from an over rich mixture, when the engine reaches normal operating temperature. The ECM will also switch on the cooling fans to prevent the engine and gearbox from overheating.
Has to be a sensor that is flipping out (too rich then too poor) and these are two sensors I know about that can do this.
MAF can also do this but you did not describe difficult starts or engine stalls.
Best of luck,
JohnMc
