IAT sensor

[zook62]

Probably not an uncommon failure here, but my '00 c5 started surging while holding constant speed and pedal position a couple weeks ago. I was expecting to come up with a fuel pump failure in the near future , but it just kept driving real goofy. If you've read my posts you know I have heads and cam, so I made sure first of all that I was into the smooth operating range of the cam and out of the jolting rpms. I borrowed the use of a scan tool, and found I had a few codes, so I cleared them and waited for the check engine light to come back on. After a drive to and from work I plugged the scanner back in to find two codes. One was p1111 and the other was p0113, being IAT sensor high voltage and IAT circuit intermittent high voltage. I at least knew where to look, so I pulled out the IAT sensor expecting to get some random resistance spikes. Nope.. It seemed pretty consistant and read between 2.5k ohms and 4.0k ohms. One thing to note is that it is a negative resister thermistor, and so resistance goes down as temp goes up and up as temp goes down... But the point was that it was consistent. Next I went to the connector. I checked for continuity in both wires. One had about 3kohms and the other had far less. So I turned the key on to check for the 5V that should be there. (the PCM sends 5V out to the MAP sensor, ECT, Speed sensors, IAT, and something in the A/C circuit) I first got the 5V, then once I moved the connector around the slightest bit my readings started going crazy. Ding ding ding! I bought the connector (probably over-paid at $27), cut about 6 inches back of the factory wires, and spliced it in. Turned the key back on and checked for the 5V. Bingo. Held just fine when I move it around too. Then it was nothing more than clearing the codes and driving off. Haven't seen it pop back up yet and the surging is gone. I should also see my fuel mileage come back. I just thought I'd share in case anyone has the same problem. It's worth checking the connector before replacing the sensor. Could save you an additional $30.

[Bigfoot]

Nice write-up.

[porvette]

Thanks for the info.