[Solved] How do I fix System Too Lean trouble code
Hey Scotty I have a 04 crown Vic that had 2 lean codes p0171 and p0174 I just changed the mass air flow sensor now I have a p0113 any idea what's wrong from my understanding the iat is in the maf
The P0113 code is saying that the PCM measured a voltage of more than 4.91 volts on the IAT sensor signal wire for more than 1 second and that's not supposed to happen.
But a 1 second glitch? I'd clear the code and see if it returns. If it does then you'll have to troubleshoot it.
The IAT sensor is a thermistor. A type of resistor. If there's a car guy out there who doesn't like to discuss thermistor circuits, I haven't met him.
The circuit for your IAT sensor looks like this.
12 volts comes into the PCM. It gets knocked down to 5 volts and goes through an internal resistor in the PCM to the IAT sensor (thermistor) and back to a Ground in the PCM.
There's a voltage sensor component in the computer (like a volt meter) that measures the voltage on the IAT Signal wire between the computer's internal resistor and the IAT sensor (thermistor).
The placement of that "voltage sensor" in the circuit makes it see this:
The higher the resistance from the thermistor, the higher the voltage it reads (closer to 5 volts).
The lower the resistance from the thermistor, the lower the voltage (closer to 0 volts).
But the IAT thermistor is always in the circuit and there's always going to be an "in spec" range of resistance (voltage measured at the Voltage Sensor) that the Pcm expects to see.
We know by the code that the "high end" is 4.91 volts.
So in your case what would cause the computer seeing the IAT sensor voltage signal approaching near or at 5 volts at its Voltage Sensor?
Well if it were a short to Ground in the IAT Signal wiring, to, or inside the IAT sensor you'd be getting a "low voltage code" (No resistance).
But you're getting a high voltage code and that means that you have an Open (broken wire or poor wiring connector) either intermittently (1 second) or always.
So like @chucktobias says, because of the location of the internal "voltage sensor" in the PCM it will see a full 5 volts if there's an Open (break) in either the Signal Wire, the Signal Ground Wire , the wiring connector, or a faulty IAT sensor (the Open in the circuit could be in there)