GM IAT and rad fan issue.. please help!
 

hey gang,

04 MSM with some mods and a rev built MS 2+

so I have two issues there and I think they are caused by a bad ground or some kind of backfeed or possibly ecu issue...

first and its prolly my stupid ass fault I haven't looked at tuner studio in a while and today I had my car plugged in due to it running off.. and the fan issue but I noticed my GM IAT was just showing 70 and would t move I had a extra sensor so I plugged it in no change... I was going to go through and test some aspects of it with my DVOM but I'm missing some of my lead tools and can't find my stash of t pins and safety pins to back probe. Will try tonight or tomorrow to find

i checked the setting tuner studio is still set up and showing its calibrated for a GM IAT.

Other issue is fans run all all the time with key on. I can pull main rad fan relay and still run but if I pull condenser fan relay they shut off.. again I know I need to go through more diagonostic with the DVOM to chase but has any one delt with gremlins like this? Any help or guidence anyone can offer please!

thank you!

-jake

Shouldn't need to back probe the IAT. It's not like a powered sensor (like a TPS sensor) that needs voltage applied to measure the output. Just pull the ECU connectors and check resistance between signal and sensor ground. Or pull the sensor and check continuity between the ground pin and chassis ground.

Pull the condenser fan relay and check continuity between the blue/white wire and ground. That's the ground wire that's triggered by the ECU. If the fans are constantly running when this relay is installed, I would expect either it's shorted to ground, or the Megasquirt is telling it to activate. Not sure why they both run, no matter whether the main fan relay is in place. Maybe a previous owner wired them to the same relay? I would just start tracing wires between the relay and ECU to make sure factory wiring is still intact. Not necessarily physically unwrapping, but just check continuity between the blue/white of condensor relay and 2C ECU pin, and between red/yellow of the main fan relay and the 2B ECU pin.

thank you! ill be diving in deeper tonight.. this car originally was a 100% bone stock MSM.. before my hands. only things altered in engine harness are unplugged sensors that are not used with megasquirt ECU and well wiring the different plug end on the IAT for the GM sensor. I got my hands on some wiring diagrams for the MSM.. I tried to attach the PDF and I believe we are late production MSM also wonder if both issues are related and its in some kind of safe mode due to no signal from IAT?

Alright so I check grounds last night for IAT check! Checked resistance for the ground wire for the IAT back to computer checked out. Also checked the signal wire and it was happy from ecu plug all the way out to IAT.
But I'm not getting 5v signal from ecu, I attempted this morning to check for 5v right at ecu by back probing connector not sure if I had a good connection but I got 0 so I may be looking at another ECU issue hopefully I can maybe solve without having to send back to Rev, but I'll check it again tonight I was a little rushed this morning trying to get off to work.

Could coolant fan running all the time when key hot maybe be sign that somethings wrong internally with ecu and it's sending IAT signal to the fan trigger instead? possibly corrupt firmware??

Any thoughts anyone?

maybe you need contact Reverant

That gentleman has MS2E and MSM and constantly running cooling fan too
https://www.miataturbo.net/megasquir...my-ms2e-93427/

I bought a used Rev MS2E for my MSM. After working out connection and firmware issues, and some troubleshooting with Rev, we concluded for sure that there's a fault in the ECU causing the fans to run non stop.

I'm waiting for Rev to give me the go to ship it back to him for repairs. It also has an external GM MAP sensor, which I don't have the proper calibrations for which I'd like to have him replace while he has it

good to know I'm not the only one with this fan issue... what about the IAT? Having any issues And if you have a GM unit are you violet/ yellow and black/red? Intake air temp 2 according to wiring diagram, That's what I have wired up and I was trying to monitor my IAT I have a manifold air temp gauge on my dashboard of tuner studio and it will only registers intake air temp sensor 1.. seems like something's off.. that shouldn't be right? How else can I access the IAT to make sure my GM sensor is working

I got frustrated with the MAP calibration settings issue and yanked it, after only just getting it running. Haven't driven it with the MS2E or done any tuning. I have 650cc injectors and EBC solenoid in hand, but I want to get the ECU back to Rev to fix the fan issue and replace the built-in MAP sensor while he's got it.

I have a GM IAT but haven't installed it yet, not sure off the top of my head, but I think it's violet/white. Got it from DIY.

Still did not get the help from Reverant?
I sent him email month go and still no answer yet.
Maybe some kind of tragedy happened - maybe he slammed his fingers in a door and can no longer type?

In my case I was doing an install of a fresh MS2E. I wired my DIYautotune GM IAT sensor to the stock wires for IAT2, exactly as you have described, but it read a constant 80F no matter what I did. I contacted Rev and he informed me that there is a jumper on the MS2E board that controls the IAT input. The jumper is located near the large white harness connector on the mainboard, and needs to be set to pins 2-3 for MSM IAT2 wiring. You'll have to pull the board out of the case to set it.

Since you have the wiring diagram, you'll probably note that regular Miatas only have an IAT1, and Rev likely configures the boards this way by default when he builds them. If like me, you are still somewhere in the install process, this may be your fix.

thank you for the feed back!! While trying to figure it last night I out i plugged the stock air box air temp sensor in and IAT 1 I got signal!! Wild Rev never told me about this issue but whatever.. i rewired my GM IAT to that and now I have good IAT! So that's good and happy, still have the fan issue but that seems it's a firmware issue..

. I have previously sent. The ecu back to have it fixed and may have to again after the summer season . I would like the fans not to run all the time seems as if they would be decreasing the efficiency of my coolant system at cruising speeds.

Either way thank you to all who replied greatly appreciated!

On the MSM your fans are set up to come on simultaneously with two speeds on the factory ecu - the only NB that does this, rather than one or the other. You'll need to find out which programmable output can control one of your fans with the particular Megasquirt that you have and then use the actual Fan Control setting for the other. In my case (crossflow fans) I ended up using the Flyin' Miata instructions for installation of said fans with Hydra, wired them that way and it allowed separate control of fans within Megasquirt. Prior to that I fought simultaneous engagement and stalling.

To comment further, when I initially installed MSPNPRO my fans were on all the time as yours are. After getting temp/output settings to where they came on and off at reasonable temperatures is when I discovered the issue with both engaging simultaneously and stalling. If you've got stock fans it might not be as bad and you might be able to run them both off just the fan control.

thanks for the input and help everyone! IAT now happy as I stated I had to change the wiring to the IAT since its taking its feed from else where... the air box IAT.. but it works took Miata down to south haven MI to Gingerman raceway for Gridlife the MSM survived and IAT and ECT temps were good. glad I added all the ducting to force air to only go through heat exchangers ECT's stayed in 190's and IATs below 100 going to address a few other things to control heat with some heat absorbing mat to keep heat out of passenger
compartment and some gold reflective tape to jeep heat away from some engine components. again thank you all... I am still waiting to hear back from REV via 2 emails I sent him regarding the ECU/ Firmware and why the fans just keep running makes no sense.

@Reverant, two of us looking for some help with MS2E fans