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Old 11-04-2015, 02:04 PM   #1
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Default HiRes 10g - GM IAT reads 300* F

I had the car running on firmware 029y4a from: Megasquirt Downloads Firmware and Software - Megasquirt EFI, and with the base map MSPNP_MM9093_Base_Map_112807 - with AFM from: MegaSquirtPNP by DIYAutoTune.com

Motor was in the process of being broken in, the only non stock item was a vtps which was calibrated. The car ran with no issues till I switched over to the HiRes 10g firmware last night.

Downloaded MS1/Extra hr_10g firmware from msextra.com and switched out .s19 and .ini file (https://www.miataturbo.net/mspnp-55/...3-hires-79606/) and flashed the mspnp. I used the mspnp mm9093 without afm basemap.

Car started up right away, but my intake air temperature gauge in tunerstudio was reading over 300* F and fluctuating. The rpms were also surging between 700 - 1500 rpm.

Not really sure what could be the issue, I'm running a GM IAT... maybe I need to use easytherm?
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Old 11-04-2015, 02:15 PM   #2
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"without AFM" already assumes GM AIT and the easy therm step was already performed for you with the creation of that .s19 firmware file.

are you certain you didn't accidentally load the WITH AFM firmware so it's configured for the OE AIT inside the AFM and NOT the GM sensor?
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Old 11-04-2015, 02:18 PM   #3
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That's what I thought as well. I'll see if there's any issues with pigtail from the gm iat.
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Old 11-04-2015, 02:54 PM   #4
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if the sensor wasn't connected it would show roughly 70F as a failsafe.
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Old 11-04-2015, 02:58 PM   #5
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Any thoughts on what the issue could possibly be?
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Old 11-04-2015, 03:25 PM   #6
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Check your IAT calibration numbers.

From DIYautotune:

◾For the stock IAT, use the following table with a bias resistor setting of 2490 ohms:
Temperature F / C Resistance In Ohms
-4 / -20 16150
104 / 40 1150
176 / 80 330

◾For the GM IAT sensor, use the following table with a bias resistor setting of 2490 ohms:
Temperature �F Resistance In Ohms
48 7000
87 1930
146 560

Edit: formatting fail
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Old 11-12-2015, 02:41 AM   #7
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So I reflashed the hires firmware and even made new .s19 file with the values on diyauto's site.

The fluctuating temperature has stopped, but the reading is off. This is with a brand new sensor.

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HiRes 10g - GM IAT reads 300* F-sqzqjz5.png  
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Old 11-12-2015, 10:30 AM   #8
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Can you backprobe the sensor with the key on and engine off, and let me know what you measure?
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Old 11-12-2015, 02:29 PM   #9
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Yeah, I'll do that tonight and I'll update my post with the values.

-Update-
So I got a value of 5.11V from one connector that was in PIN#1 in the afm connector. I'm not too sure if it's accurate because I could not duplicate the reading.

The connector on PIN#6, I was only able to read 0.0V from it. I know that leads to a chassis ground?

I also checked the pigtail for continuity and both connectors read 003-004

Last edited by .one lane; 11-13-2015 at 12:22 PM.
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Old 11-14-2015, 09:58 PM   #10
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So I went and took my multimeter to read the values on the iat.

pin1 - 5.31-5.32V
pin2 - 12V (took my red lead and placed it on the 12v power source, and black lead on connector on pin2)

The sensor and wiring should be correct?

Also, I reflashed the 10g firmware from diyauto's site and ran the 9093-no-afm base map. Now the gm iat reads -40* F? Do I need to move anything over into my working project folder?

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Old 11-14-2015, 11:00 PM   #11
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Why would you connect it to 12v? That's an easy way to blow up your ms.

That's not how you use a multimeter to test voltage.
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Old 11-14-2015, 11:09 PM   #12
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Checking for good ground?

To clarify, the car wasn't running and it was only set in the ON position. I essentially followed this video:

I'm essentially pretty lost on why the iat is not reading correctly. I went as far as flash an old firmware (029v) and loaded up the no afm base map. Now its stuck on 43*, faulty ms unit? I did recently replace the cpu.

-Edit-

Found the issue, it was one of the female connectors in the pigtail.

Last edited by .one lane; 11-28-2015 at 09:47 PM.
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