IAT sensor, what is it

IAT = Intake Air Temperature sensor. It tells your computer the temperature of the air entering the engine so that it can calculate the correct amount of fuel to deliver (colder air is denser, and requires more fuel).

It's basically a negative temperature coefficient temperature resistor (called a thermistor). The higher the temperature, the lower the resistance gets. One end of the sensor is connected to VBatt, the other is connected to your ECU. The warmer the air gets, the lower that resistance gets, and the closer the signal to the ECU gets to VBatt.

If the code is IAT Sensor High, that likely means the thermistor or circuit has shorted, connecting the ECU directly to VBatt. If you pulled some water up into the intake at any point it could fairly easily have shorted the fragile little thermistor.

This MIGHT mean the ECU thinks the air is warmer than it is and is injecting less fuel as a result, causing your performance issues. HOWEVER, injector timing is NOT a heavy function of IAT, so I really really doubt that the IAT would be causing performance issues that severe.

IAT sensors aren't expensive. Grab one from Ford or out of a wrecked car at a junkyard. That will at least make your code go away, although in my opinion it sounds like you have other problems causing the poor performance.

Oh, and if you happen to have a multimeter, here's 3 things you can do to test it:

(1) Unplug the harness from the sensor. Set the multimeter to do a continuity check. Probe both terminals of the SENSOR (not the harness). If it reads as a short, the sensor is shorted and needs to be replaced.

(2) If it doesn't, set the meter to voltage mode, turn the key to RUN (but don't start the car), and check the voltage on the Grey/Red wire (put one probe on the Grey/Red wire, the other on the chassis somewhere). You should see 12-14V. If you don't, that wire is shorted or clipped somewhere, and you'll have to investigate that.

(3) If that checks out, have an extra pair of hands help you check the grey wire. Set to continuity check again, stick one probe on the grey wire at the connector, and the other end on the grey wire at the ECU under the passenger kick panel. You should have continuity there.

I'll bet you it's #1. If it's none of the above... well... your guess is as good as mine.

Yes. It's in the crossover tube between the MAF and TB. Small little black connector, 2-wire. Sensor just slips into the rubber grommet. Just unclip the connector, and pull it out.

Have you had the entire fuel tank and pump replaced?

The sand may have contaminated the entire fuel system, thus requiring it all to be replaced.

Here's a general idea of how the code setting system works:

When the failure condition exists (ie, if you IAT was shorted), the computer will set the code as a CURRENT code, and throw a check engine light.

Now suppose that IAT short was intermittent, and the next time you turn the car on, it's not shorted anymore. That IAT code will be flagged as a HISTORY code. It will remain in the ECU as a HISTORY code, but will no longer be a CURRENT code, and the ECU will not turn on the check engine light until/unless the condition is detected again (ie the intermittent short comes back).

A couple things to consider: there are only two ways to clear a history code. One is to pull the battery. Leave the ECU without power for 10 mins and the memory and all codes will be wiped. Two is to cycle the ignition 100 times (or something like that, not sure of the exact number, but it's a lot). If the ignition is cycled 100 times without the computer observing the condition (short) again, it assumes it's fixed and clears the history code.

If you can, have the codes checked agian, and ask them specifically to check for HISTORY codes, not just current ones. If that IAT code was CURRENT 2 days ago, but now it's not even in HISTORY anymore, then that might mean that your ECU is either bad, or is losing power, because even if the IAT is no longer shorted, the code SHOULD be in history (unless you've cycled the ignition 100+ times in 2 days).

DanM said:

Yes. It's in the crossover tube between the MAF and TB. Small little black connector, 2-wire. Sensor just slips into the rubber grommet. Just unclip the connector, and pull it out.

Click to expand...

do know the color of the cables connected to the IAT sensor