Numbers look low. Check against a weather site. I'm 90-ft above sea level. I clicked on Accuweather on my iPad and the barometer at 8:00am was 30.34 inches of mercury (“Hg). If I was in my car, I could have checked the BAR value against that reading.

Low voltage can be due to the reference voltage from the PCM being too low, or a problem with the sensor. Pull the harness connector off the sensor, and key on/engine off measure the voltage between the gray wire (5 volt reference) and the black wire (ground) in the conector. Should be very close to 5 volts. There are also two other sensors the rely on the same reference voltage wire - A/C EVAP temperature and A/C pressure. It's possible problems on those circuits could affect the reference voltage,

Plus or minus a few feet above sea level is not important.

While the MAP reading is important, it's not likely to be what is causing your fuel trim issues. MAP is used for the ignition advance table, the fuel trim cell boundaries, and - if the MAF sensor sets a code - the PCM defaults to speed-density calculation of mass air flow, and that requires the MAP readings. On another note, the lack of DTC 48 when you disconnected the MAF sensor seems odd. Was the engine running when you did that? Does your scan show any codes at all?

 

I checked the barometer on accuweather for my location just now and it says 30.25. I went to check the scanner and map voltage was at 1.8 while the barometer read 28.15

Yes the car was running at operating temp when I pulled maf sensor. I even pulled the iat sensor plug and no ses came on. Only when I pulled the ect sensor ses will come on. And speaking of temp, I be getting some weird reading on my coolent temp. The pcm sees a higher temp then what the motor is actually is. Prime example, the pcm on scanner would see 205F but when i point my ir temp gun at the wp it read 159-168 (Fans on) pretty much the motor is actually cooler then what the scanner sees. Occasionally I'll get a -40 while warming up. Really odd.


Here check out my thread here https://ls1tech.com/forums/lt1-lt4-modifications/1928596-lt1-weird-issues-5.html

You will see what I'm talking about. It's a long thread.

 

The external metal temperature of the engine is NOT the same as the temperature of the coolant inside the engine. Your test is not valid. I'm amazed that no one told you that over the months you've been on there comparing the IR temp gun to the PCM. The temp gun also requires that you use the correct distance from the gun to the surface being measured, because that determines the actual area you are trying to measure.. Too far away and the gun is reading a larger area, not just the spot you are pointing it at and trying to measure. And, the readings of the IR temp gun are affected by the emissivity of the surface being measured, which is affected by color, roughness, gunk, corrosion. You have been wasting your time with your theory.

Then there's the missing air dam.... when you mentioned the temp rising with speed, the first thing someone should have asked is "do you still have the air dam?".

Your use of the multi-meter to measure the voltage and ohms is very sloppy, and indicates you have limited skills with electronics. The meter was set to the wrong scale (20K ohms) in the picture, but you thought it was set to 20 ohms. You didn't realize that 4.93 volts is close enough to the 5.0 volt reference. If you have APPROXIMATELY 5.0 volts reference with the harness off the sensor, and the resistance of the sensor - connector off the sensor - is fairly close to the corresponding ambient temp or whatever mechanism you are using to gauge the actual coolant temp, the sensor is fine, and the PCM is reporting the correct temperature. You didn't realize that you need to interpolate between the degrees and ohm values in the Shoebox temperature sensor chart in order to determine the accuracy of the coolant temp sensor.

When the PCM shows -40-degF, it is most likely due to an open circuit. It's an intermittent wiring problem. I believe at one point you stated the relationship of temperature to the resistance of the sensor. The sensor is a thermistor, and resistance changes inversely to the temperature. High resistance = low temperature, low resistance = high temperature. You can see that right from Shoebox's chart. An open circuit has infinite (very high) resistance, which the PCM interprets as -40-degF, the lowest value it is scaled to display.

After reviewing the lt1tech thread, it is totally unclear to me whether you have the correct coolant temp sensor or not. You didn't seem to believe the numbers people were giving you. Then there's the thermostat - Shoebox has a photo of the correct LT1 t'stat, and the incorrect Gen 1 SBC t'stat. Does the "mishimoto" or whatever it was match the correct photo?

Do you have the results of testing the reference voltage for the MAP sensor? That might explain why the MAP readings are too low. Since I now know you actually have a multi-meter, why haven't you checked it? This is frustrating.

Given all the problems you went through in lt1tech, it really appears that the wiring in the car is a big problem. Just looking at the bare wire in the photo of one of the sensors should have made you aware of that. Someone with more experience needs to go through it for you, hands on.... not someone 3,000 miles away on the internet.. With your limited knowledge of electronics, it's getting very difficult to help you. And the DTC 51 that showed up late in the lt1tech thread can indicate a faulty program or internal problem with the PCM. That would be a very unusual problem, that few have dealt with.

For how long did you leave the IAT connector disconnected? There is a time requirement (60 seconds minimum, 7 minutes maximum) and a minimum coolant temp requirement before the SES light is turned on. Look at DTC 23 in the factory service manual. I noticed someone on lt1tech already gave you a link to the factory service manual. Did you download it and look at the diagnostic/trouble code descriptions? Looking at DTC 15 for the coolant temp sensor, the code sets after only 2 seconds.

Was also interesting that someone recommended Scan9495 to you way back in early November. That is the kind of software/data logging that would make it MUCH easier to find many of your issues.

Not sure where to go with this. It really looks like you need to have an experienced auto electronics mechanic go through the wiring of the engine harness and clean up all the problems.

 

😂 😂 😂 I only got it cause somebody mentioned it on my thread. It wasn't my theory, I just went along to whoever mentioned it. I certainly took the wrong advice. But thanks for letting me know that

The upper part to the air dam was not bolted up. Pretty sure it was hindering in coming air from cooling the radiator. I fixed it, helped a little bit.

😂 😂 😂 Yes my electrical skills sucks, but I've learned a lot thru this whole waste of time, gotta learn some how right? I was already aware that 4.9 volts was a good range. I also tested the sensor in hot and cold water and everything checked out well.

So in my case I got the low resistance = high temp symptom. Will that trick the pcm in thinking that it's running hot? Does this have any affect on LTFT?

Reason I had little doubt cause some of those part numbers was for a 2011 Cadillac, that's what it listed in application fitment. It didn't have 95 trans am on that list. Most of gm cars has a similar looking ect sensor, at least what I noticed. I was just making sure I didn't have the wrong one. All three T-stats was the correct one, its just they hypertech one looked a little different in size.

I didn't yet, haven't had time. I Will after work tomorrow.

Well injuneer unfortunately I don't have sources like that around my area, my mechanic is always busy and he lives out of town. So sometime I got to take matters in my own hands. You got to start somewhere. Learning is the only best tool I got right now and I appreciate the help. That's code 51 was on my other pcm I brought off ebay, probably was bad to begin with.

​​​​​​I had it unplugged for not that long. Less then 60 seconds for sure, and yes I downloaded it. Lots of good info, I use everyday

Don't got a laptop, other wise I would of been using it.

 

What were the resistance measurements vs. the temperature. You posted a lot of numbers on ls1tech, but whether you had the meter set correctly, which coolant temp sensor you were testing, and whether you pulled the connector off the sensor were not clear.

I know they gave you Shoebox's link on ls1tech..... did you follow his instructions on putting the meter leads together:

The search for the correct coolant temp sensor shouldn't have been so difficult. Shoebox has the correct part # in his part listing, and that GM sensor is readily available from numerous sources. Are you aware of Shoebox's site?

You have to use the resources available.

 

I tested the ECT sensor on wp. It been awhile since I tested but if i remember the ohms range was 537 in hot water. I forgot the cold test reading. I might have did that wrong as well. 😂😂😂


So here some pictures that I took with my new scanner. It's a little more detail then the last scanner. This is data from cruising

 

Here some shots from my drive from work. My temp was at 224 F less then 20mins. I put my hand on the motor and it wasn't even hot.



Also my iac count was really low. The pictures I sent earlier it read 20 count, that's odd.

My fuel trim cell was at 16 idle. When driving at low speed it starts on 5 and the then 10 then so on. If I'm not mistaken fuel trim cell should be at 1 on cold starts right?

 

You're jumping ahead way too fast. We have to resolve the issues I raised before jumping around. Now you're worrying about your IAC count, while we haven't even resolved the engine coolant temperature issue.

Quote:

So in my case I got the low resistance = high temp symptom. Will that trick the pcm in thinking that it's running hot? Does this have any affect on LTFT?

You still have to explain what this means. Are you simply repeating your belief that the engine coolant temperature (ECT) sensor in the water pump is wrong, because it is telling the PCM that the coolant is hotter than it really is...... BECAUSE the PCM doesn't show the same temperature as your IR gun? I explained that using the IR gun on external metal surfaces was not the same as the ECT being immersed in actual coolant, and the temperatures would not match.

If you have the correct reference voltage from the connector, and the resistance vs. temperature of the ECT matches Shoebox's table, the PCM should be showing the actual coolant temperature.

But, you seem to be basing your feelings about the ECT resistance on numbers you don't even remember. And when I asked if you checked your meter by putting the leads together, as indicated in the Shoebox procedure (and I even copied and pasted for you) you never answered. Saying you got "537 in hot water" is meaningless..... HOW HOT WAS THE WATER? You have to compare the measured resistance with the ACTUAL numerical temperature of the water with the temperature read off the temp vs resistance chart.

One way to do this is to put ice cubes in a bowl of water, and stir a bit, without letting the ice cubes full melt. This produces water that is at 32-degF. When you immerse the ECT in the water, you should get 9,420 ohms (+/- 10%). Then boil water on the stove, keeping the burner on. Since you are very close to sea level, the boiling water is at 212-degF. When you immerse the sensor in the boiling water, you should get 177 ohms. Shoebox also tells you how to judge the coolant temperature by letting the engine sit overnight, and measuring the sensor resistance before starting the engine, because it should match the ambient temperature.

Quote:

I tested the ECT sensor on wp.

I know that. But in the ls1tech thread it appeared you have more than one sensor that you had installed, one that you thought was for a Cadillac, maybe a couple of others. Which of those sensors did you test (maybe unimportant since you didn't record the results)? Was it the one currently installed in the engine?

 

Sorry Fred I'm a newbie when it comes to this electrical stuff lol.

No I'm pass that, you explain that the ir gun is wrong and not accurate so I get it and I'm not being basing at all, I probably did it all wrong. Like I mentioned above I'm a newbie when it come to this electronic testing stuff, just bare with me fred lol.

It's been raining and I got a 2 year old boy that has loads of energy. Probably why I haven't had got back to you on that, my apologies.

I went over that shoebox procedure like 100 times, I was just doing the TESTING WRONG.

This morning before I started the motor (First Start Of The Day) scanner read 80 degrees in a 60 degree weather, I would think it should match or be close to the outside temperature. I also read the ECT sensor and the IAT should be close in range.

IAT read 58 degrees which was closer to outside ambient temperature vs the ECT sensor temperature

​​​When I was driving home my temp SPIKED from 180 to 184 in seconds. It would go down slightly going 80 mph. But around 50 mph (City traffic) it slowly creeps up. I'm gonna check the T-stat when I'm off.

Those was all my old ECT sensor (Actually Not that old) that I had sitting in my room.

 

I got some update on the temp rise.

So while looking around the radiator I found a plastic bag in between the condenser and radiator.

I'm pretty sure that's PART of the reason my temp rise while cruising.
I wonder how long it's been there..
These fbody are great at sucking up trash.