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Old 03-09-2008, 01:20 AM   #1
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Default No CLT Reading

I am so close I can taste it. Car is squirting barely, but I get a -40*F for the CLT. I have MS1v3 running standalone. I'm using the DIYAutotune firmware for the PnP with their easytherm values and their MSQ.

The megasquirt sees a temprature with the stim.

I took the CLT sensor out of the car today to make sure it was in spec, and the resistance matches up with what I had in the enthusiast's manual for different temperatures.

I have triple checked my harness, and MS pin 21 goes to 3G on the factory harness.

Now I am thinking it has to be that the factory harness is messed up or the DIY easytherm values aren't doing it for me.

I was having this same problem before with the values from brainiack's FAQ:

Quote:
If 96-97: Resistance scale pending.

If piggyback with R7: Use 790 for CLT and xxxx for AIT for the bias.
If piggyback without R7: Use 1544 for CLT and xxxx for AIT for the bias.
If standalone: The bias will be 2490 for each.
I noticed it said resistance scale pending. Does someone else have better values? If no one has better values, would it be beneficial to us 96-97 guys for me to pull the CLT to get better values? It wasn't that bad, and I could do it again.

How could I test the factory harness? Get some long leads for the DMM and see if there is continuity from the connector to the ECU plug?

Or could I be missing something really simple, or missed a thread that has already covered this?
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Old 03-09-2008, 01:36 AM   #2
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The only reason you would be getting zero reading (-40) for the CLT is if you don't have continuity between the MS and the sensor. So yeah I would test the continuity of the stock harness and see what you get.
Testing your sensor out of the car to get your own resistance curve works but there are many accurate curves in use right now you can find them in the mspnp .inc files or use the rx7 defaults, both are pretty close. Use w/e at your own disgression and experience.
Don't forget, you also need to put the .inc files from the MSPNP folder into your mtcfg folder in order for megatune to read your sensors accurately.
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Old 03-09-2008, 01:42 AM   #3
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Thanks for the clarification. I'll check continuity when I get a chance tomorrow then, and see what happens.
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Old 03-09-2008, 07:45 PM   #4
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There is continuity from the sensor connector to the ecu connector.

I tried swapping firmware and had some interesting results. Using an easythermed HiRes code I lost IAT and CLT. I used the GM values for the IAT, and the RX-7 values for the CLT. They both were showing nothing. When I went back to the MSPNP firmware the IAT came back, but I got nothing from the CLT. I did notice that IAT was about 14*F off.

I got no idea what is going on...
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Old 03-09-2008, 08:16 PM   #5
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Well if CLT is working when on the STIM then I would check your soldering on the harness and make sure you've got the correct wires going to the correct pins. Check continuity from the DB37 pin to the CLT sensor connector. Stick a lead in the DB37 and test it that way.
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Old 03-09-2008, 10:03 PM   #6
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I've got continuity from pin 21 on the db-37 to the connector on the sensor. I also turned and twisted both connectors to make sure there wasn't an extreme the wires were getting pulled to causing a short.

I will throw out there that with the stim I don't get the full range of the gauge on the screen, but it covers that majority of the range.

Thanks for your help so far cjernigan.
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Old 03-09-2008, 10:25 PM   #7
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Post pictures of the top of your board unless...

Do you have R7 installed? I don't think you will get a coolant reading without R7 installed.
You only leave out R7 on parallel installs.
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Old 03-09-2008, 11:08 PM   #8
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I've got r7 installed.

There is no fan mod installed yet. The transistor for idle control is only like that temporarily.

There is still flux on the board. I left it huge so you could see details if you need to. If there is any other areas you need close ups of let me know.


http://screaminmiata.googlepages.com/DSCN0837.JPG


Edit: Wow.. when you see it at that resolution it looks extremely dusty and dirty. Should I clean up the flux?
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Old 03-10-2008, 11:04 AM   #9
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If you've got continuity from one side of the sensor to the MS, then the other side of the sensor isn't grounded.... or the sensor is dead, or the connector is bad and isn't making a good connection.

-40 degrees means the circuit is open.
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Old 03-10-2008, 12:38 PM   #10
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FWIW, I had a similar problem after my engine swap. I found the problem to be the connector to the coolant sensor at the back of the head. Somewhere along the way one of the spade connectors fell out of the plug that hooks up to the sensor so double check the plug to make sure there are two metal contacts inside it. Mine only had one and when I spliced in a spare plug with two metal contacts, all was well. I hope it's that simple.
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Old 03-10-2008, 12:54 PM   #11
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Any idea where the sensor grounds to? The wiring diagram shows it grounding to junction connector (right side of I/P). What is the I/P?

The Enthusiast`s Shop Manual lists some resistances at different tempratures.
If I remember correctly I tested it around 60*F and 170*F. The resistance was maybe off 50-100ohms in each case. I would think if I was getting any resistance from the sensor it would show up differently than -40. Should I just replace it?

I can't remember if I have mentioned this but the car runs fine with the stock computer. Would an OBDII code be thrown for a lack of a CLT sensor reading?
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Old 03-10-2008, 01:06 PM   #12
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The sensor isn't the problem if the resistance was changing and was only 50-100F off. If the sensor was bad you wouldn't get readings that accurate. Something else has to be haywire.

The sensor should be grounding on the intake manifold somwhere along with the stock ECU and all of the other sensors. You can access the madracki diagrams in my signature to get the wire color and location of the ground for your year car.
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Old 03-10-2008, 07:59 PM   #13
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The wiring diagram says the blue/black(clt ground) wire connects to the junction connector (right side of I/P).

Does anyone know what an I/P is?

I can only find two grounds on the intake manifold and neither one has continuity with the coolant temp sensor.

I checked the blue/black wire on the other sensors (TPS,O2 sensor,MAF,EGR position sensor) I could get to that share the common ground according to the wiring diagram, and they all had continuity with the CLT.
Attached Thumbnails
No CLT Reading-ground.jpg  
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Old 03-10-2008, 08:43 PM   #14
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why not pull the connect, put a jumper across it and see if you get a different temp.
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Old 03-10-2008, 08:50 PM   #15
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All grounds should have continuity on the car.
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Old 03-10-2008, 09:23 PM   #16
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Quote:
Originally Posted by Braineack View Post
why not pull the connect, put a jumper across it and see if you get a different temp.
Good idea... I'm going to try it now.


Quote:
Originally Posted by richard_ha
All grounds should have continuity on the car.
Therefore if the ground of the other sensors have continuity with the CLT's ground then the CLT should have a ground. Unless the common ground of all of those sensors was not grounded, but I seriously doubt that.
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Old 03-10-2008, 10:08 PM   #17
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Alright I've got some interesting results.

With the connector for the CLT jumpered across both pins I got nothing in Megasquirt. With pin 21 from the Megasquirt jumpered to the engine I got a temprature. So bad ground right?

The plot thickens...The IAT was showing 43 degrees which is what it was showing yesterday and the MAF nor the IAT were plugged into the harness. Now that I think about it the IAT always shows 43 degrees regardless the outside temprature. The MAF and the CLT ground to the same point.

WTF!
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Old 03-10-2008, 10:09 PM   #18
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What pins did you ground on the DB37 harness?
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Old 03-10-2008, 10:17 PM   #19
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These pins are grounded on the DB-37:

7, 8, 9, 17, 18, 19

As per Braineack's Howto, I bet that is just for parallel.


Should I have 7,8,9,10,11,19 and maybe 17,18?
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Old 03-10-2008, 10:31 PM   #20
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No, those pins are fine. I'm running out of ideas here though.
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