Nothing is more annoying than scrambling trying to find calibration data for sensors on the dyno. This happened to me last week. I noticed the IAT on a turbo vehicle was reading around half of ambient. Asked the customer and he mentioned it had a RIFE Lo-AT sensor so I go to check the cal data and to my surprise there is none in gen 3 format. I had to find the factory GM sensor calibration and generate my own, this took a good 15 minutes that shouldn't have. So here I am providing the cal data for anyone who may be interested in it.
| Percent (%) | 0.0 | 6.2 | 12.5 | 18.8 | 25.0 | 31.2 | 37.5 | 43.8 | 50.0 | 56.2 | 62.5 | 68.8 | 75.0 | 81.2 | 87.5 | 93.8 | 100.0 |
| Temperature (°F) | 335.0 | 325.9 | 264.9 | 231.4 | 207.7 | 189.0 | 173.1 | 158.9 | 145.8 | 133.1 | 120.7 | 107.9 | 94.3 | 79.0 | 60.2 | 32.9 | -10.0 |
I know the temperature exceeds the limit of the first two column cells (0,6.2%), but that's just how the cal plays out. I will include a downloadable excel spreadsheet for those who want to have the excel saved under your gen 3 tuning folder, HERE.
Here is the OE Cal:
From the known resistance-voltage pairs in the GM factory data we can determine that it uses a 2.2k ohm pull up. The way it works is :
5 V > internal pull-up resistor > IAT signal > thermistor > ground
The PCM measures the voltage in the middle. For that circuit:
So if we rearrange it to solve for the unknown PCM pull-up:
For 185 ohms at 0.38 V:
So, 2.2k ohms.
Why is this important? Well the P01/59 measures voltage, not resistance. In order to find the % (voltage value)-temp in the factory table, we need to know the total resistance. We can't assume 0. For example: The RIFE sensor might be, say, 2,200 ohms at a particular temperature. With a 2.2 k ohm pull-up
And 2.50 V on a 0–5 V input 50%, you then find the temp value that corresponds to 2200 ohm and insert it in the 50% cell.
If you had assumed no pull up, we would have 5V, or have that value in the 100% cell which is incorrect. Anyways, I hope this helps one of you guys.