liamjoseph2

Okay so,
I have an issue where my stock coolant temperature sensor won't show up in MS and is stuck at 180F. I calibrated the sensor in MS to "mazda" and it didn't change anything. I tested the sensor by dunking it in some hot water and the stock gauge on the car still moves/works, so that means the actual senor works correctly? I'm not sure what to test next as I'm relatively new to car wiring like this.

Also, potentially unrelated, I've had a difficult time getting the car to start with the base map. I believe I correctly set up my injectors and changed all required setting for startup following the "MegaSquirt PNP Pro Documentation" for my MS3PNP. Because the sensor doesn't work I manually changed the enrichment to what it would be at room temp and it still doesn't start for more then 1 second. I'll attach my map if anyone wants to take a look.

Any advice on the 1st or 2nd issue would be greatly appreciated, because I've searched the forms and directly messaged the DIYAutoTune tech support and still haven't gotten vary far.
Thanks.

SimBa

At least on Speeduino the coolant temp defaults to 180 if no sensor is detected. If your PNP is for an NB1 I'm not sure why the sensor wouldn't be picked up assuming you're using the stock wiring harness.

Can you keep the car running with the throttle? Posting a log of the car starting/dying is going to give way more insight about what's going on then just the tune file.

liamjoseph2

Thanks for the reply, your cars setup is very similar to mine except I have a kraken low mount.
In in regards to the coolant sensor, that's the same conclusion I came to, that's why it's so confusing why it's not being picked up. I don't have much of the stock harness messed with. All the ECU cables are untouched going into the MS.

I cannot keep the car running with throttle unfortunately, I've been experimenting with different trigger angle offsets because I can't keep the car running long enough to set base timing in MS. I'll definitely see if I can take a data log (once I google how to do that lol) and post it. Right now I'm letting my battery charge back up from cranking the engine a bunch.

Thanks again for your help

curly

iTrader: (25)

The coolant sensor is on the injector harness. It’s not unplugged, is it? And the ground by the throttle body is also for the injectors/coolant sensor. That’s not loose is it?

liamjoseph2

Thanks for the help guys,
I got the car to start for a brief period of time using the throttle and took a data log, I'll attach that here.
As for the injector harness, I checked for any unplugged wires and didn't find anything suspicious, and I ensured the ground connected to the throttle body was secure.

But the coolant temp sensor still reads 180F/doesn't work, so any other suggestions are appreciated.

SimBa

Have you tried adjusting your duty cycle at idle? At least on my NB1 (on speeduino fwiw) I idle a bit above 30, where your tune is set to around 14. You also have crank to run set to 9 seconds, which seems like a lot, but take that with a grain of salt. I'm far from a professional.

I assume you're trying to set base timing? Your timing is locked at 10 degrees, but your idle cells are around 25. Again, this seems really high. I'd usually idle around 10 degrees, so unless there's some correction dropping the advance down I would probably lower that.

Is this a base map for your car/PNP? Where did you get it?
Also, any more details about the car? Some of the tables (ignition) have cells for boost and others don't (fuel).

liamjoseph2

Thanks for the tips, I'll try and change some of those setting around and see how it goes.
This is mostly the 99'-00' base map from the DIYautotune site, expect I changed some settings for my injectors and I put in the ignition and fuel maps from a Mazdaspeed miata (because I'm running boost and they go up to 200kpa), but when it wasn't starting I changed just the fuel map back to normal but the ignition map is still from the Mazdaspeed miata tune. oh and I'm artificially enriching the mixture by setting the enrichment to what it would be at 77F at 180F because the coolant temp sensor doesn't work. If I can get it idle well enough I may be able to change that back and run it without a coolant temperature sensor for now.

liamjoseph2

Okay, I changed the things you suggested and it runs a lot better and almost idles. Unfortunately because it's the first time it's run for a long period of time I've discovered that my oil feed is leaking. So now I have to take off the low mount (which is a huge pain in the ***) so my progress is halted for now until I get that done.

Still very open to suggestions for fixing the the coolant temperature sensor issue though. That's pretty much the last thing that I don't know how to fix right now.

SimBa

Sounds like a step in the right direction. I'm still not sure why the coolant sensor wouldn't show any values Keep us posted.

curly

iTrader: (25)

Don't bother making any tuning changes until the coolant sensor is fixed. There's tons of settings that are coolant based, so you'll be making changes for a car that's at 180 that's not actually at 180.

Unplug the sensor, check continuity on the pins to ground, one should have continuity. Check the other to your ECU's coolant temp sensor pin. If there's good continuity to that pin, then check temp with it unplugged, it should read min temp, usually -40. Then jump the two pins together with a paper clip, it should ready max temp, usually 255.

If there's bad continuity, you've got a wiring issue. If wiring is good and the -40/255 tests don't work, it's an ECU issue. If they both check out ok, it's a sensor issue.

liamjoseph2

Alright so this is the information I have for the CLT sensor,
The continuity to ground is good. The continuity to pin 3E is good (from the red/blk wire). Jumping the 2 wires that are not ground (the signal wire red/blk to 3E, and the other wire purple/white) does nothing/stays at 180F.

So does this mean I have an ECU problem? I added a photo of a drawing of my understanding of the wiring from the CLT sensor.

(I'm also not very proficient in wiring so I may have done something wrong, I literally had to buy a multimeter to do this lol.)

curly

iTrader: (25)

purple/white goes to the cluster, it's irrelevant to the ECU.

blk/red is the ground as you said, but the signal should be red/blue. I don't think you've said which NB you have (oops I see it in the title now), but NB1 and NB2 are both the same. My guess is your blue is a little dirty, making it look black/red instead of red/blue. Anyways, semantics done.

I'm guessing by 3E you mean 2E? That's where your coolant temp input goes.

Ah, I'm researching as I'm writing this. MSPNP pro documentation labels the plugs 1, 2, 3, and 4, but OE documentation only lists 1, 2, and 3. Your MSpnp PRO adds a plug for options, read here for their pinout:

https://www.megasquirtpnp.com/docs/m....php?isModel=1

They call this plug 2, renumbering OE plugs 2 to 3, and 3 to 4. Very dumb.

What's REALLY dumb is I can't seem to find a way to reassign the CLT sensor to any other pin, but you could jump it to the IAT pin either at 2B (3B if you're looking at DIY's documentation), or the rear connector pin E. Do this with your IAT sensor unplugged. Again when unplugged you should see your IAT jump to -40, and when you jump the CLT sensor to the IAT pin, it should start reading coolant temps. If it does, unfortunately we've sort of identified the ECU as having a hardware issue, and you'll need to contact DIY for repair*. You can then do the same test with the paper clip again to see if it reads 255.

*I am a semi-professional complete amateur, my diagnostics should not be taken as 100% accurate.

liamjoseph2

Thank you so much for doing this research for me,
Yah the stock wiring diagram was confusing me a lot for that same reason, I had the MS3 documentation pulled up at the same time as the stock wiring diagram and I couldn't figure out anything lol.
When I have time I'm gonna try your idea to connect the CLT sensor to the AIT sensor and see what results I get.

I've also been in contact with the DIY tech support and the guy on there seems to think it could still be a sensor or calibration issue, I asked him to elaborate how I would test those and he hasn't gotten back to me yet.

liamjoseph2

Ok I connected the AIT sensor to the CLT sensor with the same calibration and it was reading 95 degrees in the air which seems relatively appropriate because it's supposed to be in coolant. So that seems to rule out the sensor itself because its outputting a reasonable number.

I think I might have to bite the bullet and send it out to DIY, there goes at least 2 weeks probably from me driving the car.

liamjoseph2

OK so here's an interesting update,
I was out messing with the car and randomly the coolant temp gave me a signal on MS. It was reading -38°F, so I was like that's very cool but definitely not right. I messed with the calibration and it starts reading room temperature when you set the base resistance to like 50-500ish range it will jump around a ton. And sometimes when you put the calibration back to "normal" it will jump right back to 180°F I assume that's because the signal falls below -40°F or something.
The strange part about this is, when I tested the sensor via the air intake temperature sensor plug it was reading relatively normal at the "correct" calibration so I have no idea what's going on. Maybe it's an increased resistance in the signal wire? Maybe it's still the ECU?

Any insight is appreciated.

curly

iTrader: (25)

Temp sensors are resistance based. If you put one in a pot of ice water, turned the burner on, and checked resistance across the two contacts, you'd see it go from ~6000ohms to ~200ohms once at boiling. For whatever reason, the easiest way for our ECUs to read this resistance is to turn it into a 0-5v signal. They do this by adding a pull-up resistor around 1k ohms between 5v and the signal, so ice water reads ~4.2v and boiling water would read ~.78v.

I'm looking at a calibration table for a specific sensor, so don't quote these resistances and voltages for Miata coolant sensors, this is just an example.

Sounds like your pullup resistor is burnt out, soldered poorly, or similar. I don't think I've missed something more obvious in our diag in this thread, but I've been caught with my diagnostic pants down before. Usually someone else chimes in with ideas I've missed, but for whatever reason you've been stuck with just me responding.

I'd jump the coolant sensor to the AIT input again, and try applying some ice or heat to the sensor to see if it's responding appropriately. And I'm assuming when the AIT is disconnected and shorted, you're getting -40/255 respectively?

liamjoseph2

Hey thanks for responding,

I will definitely double check the response of the CLT sensor via the AIT plug tomorrow with some heat/cold. I'd expect it to respond appropriately though based on my other observation.

So about the pullup resistor, is that a park of the ECU or a part of the chassis? And how would one go about fixing that?

Also I ended up buying another CLT sensor anyway just for ***** and giggles, so when that comes in from moss miata i'll see if that does anything (it probably won't based on the diagnostics but I can dream lol).

Thanks again for the help, I literally would be making zero progress without your help.

SimBa

The pull-up resistor would be part of the ECU. It is used to "pull-up" the circuits voltage to - I assume - 5 volts. I believe this aids in stabilizing the readings of the sensor. Even having taken courses on this in college (computer engineer) I admit that I don't understand all of these concepts as well as I'd like.

I'll let Curly take the lead on this one, as I don't have megasquirt experience, but I would assume you'll need to pull your ECU and open it up to inspect the solder joints. Hopefully there are schematics for the ECU available so you can get an idea of where to look.

Depending on when/where you got your ECU you might contact the manufacturer and see what they think and if they could fix it for you (unless you want to do it yourself).

liamjoseph2

Hey guys,
So I double checked the AIT connector and the CLT senor and they all read appropriately/as expected. So I'd have to believe it is an ECU problem at this point. So I will take a look inside the ECU and check where the pull up resistor is located and see if it's something obvious that I can fix, but it most likely won't be and I'll have to send it to DIY.

On a more positive note, since I could get the sensor to actually read actually something I tried to start the car when it was reading -30°F, and that thing jumped to life and idled perfectly at 1500RPM. So it seems like the base tune from DIY is good and I just need to have a working CLT sensor lol.

liamjoseph2

Hey guys, so I sent the ECU to them and they confirmed the issue and said they resodere4de and cleaned the connections and it started working. They did inform me that the board didn't look to be in great condition so if other things or the same issue arises again he recommend buying a new board. BUT it seems to the working ok now.

My other issue now is the car is having a hard time idling/running and is running lean. I think its having to do with the tuning of the fuel and spark maps. The stock spark map seems to be kind of high, its idling at like 25 degrees advanced on the base map. If anyone has an example spark map file for a 1.8 that I can import into megasquirt that would be helpful.

Thanks for all the help guys couldn't have gotten this far without you.