01-14-2009, 11:58 PM
Join Date: Jul 2006
Location: Central California
Total Cats: 0
GM IAT failure?
I have been seeing temperatures about 20* higher than expected from my GM IAT. The sensor is wired directly, grounded at ecu ground by the TB and the other going to megasquirt. I am using GM settings and 2490 bias.
Tonight I ohm tested the sensor in boiling water and found that it read around 240 ohm. In Ice water, it reads 7640. According to the chart below, the sensor should be reading closer to 180 and 10500 respectively. The ohmmeter was tested against a 270 ohm resistor to assure that it was functioning correctly. It read 266 for all 3 resistors tested, which is within the 5% tolerance spec.
Aside from being almost exactly 20* off, the sensor seems to act normally, so can I simply use these numbers ive gathered, and adjust adjust the temperature I input to easytherm by about 20* for the middle one?
212 -> 240ohm
32 -> 7640ohm
... wait as i am doing this, it is seeming more complicated. the curve has been thrown off and it is not 20* off everywhere, its about 8* off at 32 and 20* off at boiling... help me get that middle value right someone, my math sucks
Last edited by akaryrye; 01-15-2009 at 12:03 AM.
Reason: gm temperature sensor bias