Intake Temp -40F
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Intake Temp -40F
I was sooo pissed off. Jerry and I were working on some ground and ignition issues, and I thought I was finally going to get a chance to really test the car out since making some modifications. Not so lucky, MegaTune reports Intake temp is stuck at -40F.
I assumed that the most likely issue would be a failure in the connections between the temp sensor wiring and the AFM harness. So I opened that up (which was a PITA due to the 50lbs of electrical tape I used to mumify the connection). But alas, the connection was sound. The other connections seemed solid, but I didn't have time to conduct further investigation; I've got family in town.
The intake temp sensor is a GM open element. I assume it's just a thermistor. Does anyone have a reference chart (V vs temp) to check the sensor for proper operation?
This never happens when it's 70F outside. Nope, it waits until it's 100 so I have to sweat my *** off.
I assumed that the most likely issue would be a failure in the connections between the temp sensor wiring and the AFM harness. So I opened that up (which was a PITA due to the 50lbs of electrical tape I used to mumify the connection). But alas, the connection was sound. The other connections seemed solid, but I didn't have time to conduct further investigation; I've got family in town.
The intake temp sensor is a GM open element. I assume it's just a thermistor. Does anyone have a reference chart (V vs temp) to check the sensor for proper operation?
This never happens when it's 70F outside. Nope, it waits until it's 100 so I have to sweat my *** off.
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seems ok, didn't have a lot of time. I had continuity between the two wires, and did not have continuity between either wire and chassis ground. did not check for resistance or voltage.
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i could buy failed sensor, but doubt MS software/firmware issue. That's why I was hoping someone had temp vs voltage data for the thermistor. Becuase then I could put it in a pot of hot water and compare voltage output to a thermometer.
I should have clarified, with the 2 wires from the sensor not hooked to anything else, I had no continuity to ground. Meaning I didn't have a short to ground.
I should have clarified, with the 2 wires from the sensor not hooked to anything else, I had no continuity to ground. Meaning I didn't have a short to ground.
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do you have a multimeter? That would help quite a bit. As for the resistance you are looking for, why not open up easytherm and look at the GM default values. Also, I cant verify that it is correct, but it probably is, I found this after a quick google search. Looks like just what ya need: http://www.innovatemotorsports.com/f...php/t-988.html
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cool, thanks ryan. that was what i need. so in ambient 90-something I should get around 2.3-2.4V.
F Volt
304 0.000
260.6 0.016
226.4 0.312
199.4 0.468
179.6 0.624
163.4 0.780
152.6 0.936
143.6 1.092
136.4 1.248
129.2 1.404
123.8 1.560
118.4 1.716
113 1.872
109.4 2.028
102.2 2.184
96.8 2.340
91.4 2.496
84.2 2.652
77 2.808
71.6 2.964
64.4 3.120
59 3.276
53.6 3.432
48.2 3.588
42.8 3.744
37.4 3.900
32 4.056
24.8 4.212
17.6 4.368
5 4.524
-9.4 4.680
-29.2 4.836
-58 5.000
304 0.000
260.6 0.016
226.4 0.312
199.4 0.468
179.6 0.624
163.4 0.780
152.6 0.936
143.6 1.092
136.4 1.248
129.2 1.404
123.8 1.560
118.4 1.716
113 1.872
109.4 2.028
102.2 2.184
96.8 2.340
91.4 2.496
84.2 2.652
77 2.808
71.6 2.964
64.4 3.120
59 3.276
53.6 3.432
48.2 3.588
42.8 3.744
37.4 3.900
32 4.056
24.8 4.212
17.6 4.368
5 4.524
-9.4 4.680
-29.2 4.836
-58 5.000
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well theres your problem right there, I bet there are available sensors for like 10 bucks at the dealership. Wait, make sure that you are getting the 5v reference voltage from megasquirt first, but its kinda hard to screw up a temperature sensor wiring.
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I should have 5V between the 1st and 6th pins on the AFM harness, right? (those are the ones that the temp sensor hooks to)
I have 0V there.
The thermisistor does change resistance with ambient temp. I had 4000k ohms outside and 3600 ohms inside
I have 0V there.
The thermisistor does change resistance with ambient temp. I had 4000k ohms outside and 3600 ohms inside
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Right, but it's a circuit so it needs power. Should be 5V goes in, the thermistor adds resistance based on temp, so less than 5V comes out. Resistance decreases as temp goes up.
My sensor does change resistance based on temp, it seems. R should decrease as temp goes up. However I'm getting some mixed readings, but probably due to the fact I have to hold it in my hand.
MY MS shows -40F which is the bottom of the scale. Which would mean 0V/infinite resistance.
I have 0V at the AFM harness. There is a connection somewhere. I do not know which pin at the ecu suppies 5V to the AFM, but suspect (hope) that's where the problem is.
My sensor does change resistance based on temp, it seems. R should decrease as temp goes up. However I'm getting some mixed readings, but probably due to the fact I have to hold it in my hand.
MY MS shows -40F which is the bottom of the scale. Which would mean 0V/infinite resistance.
I have 0V at the AFM harness. There is a connection somewhere. I do not know which pin at the ecu suppies 5V to the AFM, but suspect (hope) that's where the problem is.
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Right, but it's a circuit so it needs power. Should be 5V goes in, the thermistor adds resistance based on temp, so less than 5V comes out. Resistance decreases as temp goes up.
My sensor does change resistance based on temp, it seems. R should decrease as temp goes up. However I'm getting some mixed readings, but probably due to the fact I have to hold it in my hand.
MY MS shows -40F which is the bottom of the scale. Which would mean 0V/infinite resistance.
I have 0V at the AFM harness. There is a connection somewhere. I do not know which pin at the ecu suppies 5V to the AFM, but suspect (hope) that's where the problem is.
My sensor does change resistance based on temp, it seems. R should decrease as temp goes up. However I'm getting some mixed readings, but probably due to the fact I have to hold it in my hand.
MY MS shows -40F which is the bottom of the scale. Which would mean 0V/infinite resistance.
I have 0V at the AFM harness. There is a connection somewhere. I do not know which pin at the ecu suppies 5V to the AFM, but suspect (hope) that's where the problem is.
IF 5V is been supplied power... based on the scale you posted... MS is reading 4.9XXXXX. Should then you voltmeter been reading say 5v across since that is what -40 means? It sounds to me like you where probing the wrong pins. 0V should read 300F not -40.
Maybe I am getting everything flipped in my head, I am still ******* dead, but that was logical pops first.
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the scale below is wrong. web info isn't always right, as that's not how a thermistor works. its resistance approaches 0 as temp increases, and resistance apporaches infinity as temperature decreases. The MS is supposed to supply the thermistor 5V, the thermistor will drop the voltage, and the MS calculates delta V to determine temperature.
I think the thermistor works, but it's not receiving power.
I think the thermistor works, but it's not receiving power.
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Jerry, If/When you read this, could you please post which wires at the ECU harness go to the pins at the AFM connector that we plug the AIT sensor to? I'd like to probe out the +5V source for functionality, and then just directly wire from the MS to the AIT sensor without going through the AFM wiring. Assuming there's no type of filtering circuit in the AFM harness--which I doubt is the case.