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V1 Captain Dave's City Goblin #336 - 07 SS/SC Donor

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You need a diagnostic scanner or something like hp tuners to see the live data. Even most of the cheaper ones will read live data. But not all the basic code readers will.
The diagnostic procedure could be different between the base Cobalts and the SC. There have been multiple post with links to free oem manuals on here or you can get an all data subscription or acdelco tds subscription. I don’t know that there are differences between base and sc but you can’t assume they are the same.
 
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Gtstorey said:
You need a diagnostic scanner or something like hp tuners to see the live data. Even most of the cheaper ones will read live data. But not all the basic code readers will.
The diagnostic procedure could be different between the base Cobalts and the SC. There have been multiple post with links to free oem manuals on here or you can get an all data subscription or acdelco tds subscription. I don’t know that there are differences between base and sc but you can’t assume they are the same.
Click to expand...
Ok thanks. I do not have any experience using a diagnostic scanner but I am sure I can figure it out with the help of YouTube. lol. If not I may just take the car to a shop that has the capabilities to scan it for me. I guess the thing that is really not clear to me is that if I do have a reading that is out of the acceptable range, what would be the next step? Would that mean the PCM is not providing the correct voltage? Probably not so easy to diagnose like that.
 
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One thing that I just thought about that has a small possibility of causing a problem with the car is that when I switch the car on the 4 way flashers start blinking and the horn goes off for about 15-20 seconds. I am guessing that is some sort of security feature but if so why does it just stop after 20 seconds? How can I diagnose that issue and make it stop? Could that be the whole throttle issue?
 
Robinjo
Captain Dave said:
One thing that I just thought about that has a small possibility of causing a problem with the car is that when I switch the car on the 4 way flashers start blinking and the horn goes off for about 15-20 seconds. I am guessing that is some sort of security feature but if so why does it just stop after 20 seconds? How can I diagnose that issue and make it stop? Could that be the whole throttle issue?
Click to expand...
Yeah, that doesn't sound right at all. You'll have to see what the tool scans for. Hopefully it can give you an idea where to look.

Did the previous owner do the wiring harness work or did they send it in to DF for work?
 
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Robinjo said:
Yeah, that doesn't sound right at all. You'll have to see what the tool scans for. Hopefully it can give you an idea where to look.

Did the previous owner do the wiring harness work or did they send it in to DF for work?
Click to expand...
Previous owner did it. I’ve already had a couple of small issues with the wiring but nothing major.
 
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Did some more poking around on the PPS wiring today and used the probes Ross recommended. I found that PPS 2 is not getting any power from the PCM. PPS has the correct 5V coming out. Seems like a PCM issue with this discovery right?
 
G
PPS is pedal position sensor? Have you confirmed your wiring diagrams with the correct ones for your donor/ecm, not the one that you linked earlier for the base? The APP won't generate voltage on its own, so it has to have something supplying it power.
 
Ross
The LSJ PCM has two 5V circuits. Either circuit can be dragged down to 0V if there is a wiring issue, or a bad 5V sensor. So you need to do more testing before we can determine if it is a bad PCM.
 
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And there is likely two 5V feeding into the APP so your determination that the APP has 5V coming out could be the second 5V coming into it. This may be what Ross is trying to point out.
 
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Ross said:
The LSJ PCM has two 5V circuits. Either circuit can be dragged down to 0V if there is a wiring issue, or a bad 5V sensor. So you need to do more testing before we can determine if it is a bad PCM.
Click to expand...
At a minimum there should be 5V coming out of the PCM right? I am testing in the plug that is connected directly to the PCM. Only one of the power source wires has the 5V at the PCM. The other power source is not giving any voltage readings. I even checked all of the other wires from the PCM to the PPS just to be sure something wasn't wired incorrectly.
 
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Gtstorey said:
PPS is pedal position sensor? Have you confirmed your wiring diagrams with the correct ones for your donor/ecm, not the one that you linked earlier for the base? The APP won't generate voltage on its own, so it has to have something supplying it power.
Click to expand...
Yes I have confirmed the wiring diagram for my specific car. I am testing at the PCM which is where the power originates from and then goes to the PPS. I have 5V on one of the APP sensor wires coming from the PCM but nothing out of the other APP sensor.
 
G
You need to disconnect everything off the 5V reference that doesn't work and recheck. It could be shorted to ground and you would not get a voltage reading. I would probably cut the wire to confirm no voltage before I called a bad PCM. But they do fail.
 
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Gtstorey said:
You need to disconnect everything off the 5V reference that doesn't work and recheck. It could be shorted to ground and you would not get a voltage reading. I would probably cut the wire to confirm no voltage before I called a bad PCM. But they do fail.
Click to expand...
Where are you talking about cutting the wire? Are you saying that if there is short between the PCM and the PPS that could prevent an accurate reading coming directly out of the PCM? If that is the case I could cut the 5V wire right after it exits the PCM and retest.
 
Ross
From Charm Li, Here is the two 5V circuits going to the accelerator pedal. So which circuit isn't working?
If it is circuit 1, then all the sensors on the left are part of it.
If it is circuit 2, then all the sensors on the right are part of it.
There probably is more sensors, but we would need to do more digging.
53868
 
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Captain Dave said:
Where are you talking about cutting the wire? Are you saying that if there is short between the PCM and the PPS that could prevent an accurate reading coming directly out of the PCM? If that is the case I could cut the 5V wire right after it exits the PCM and retest.
Click to expand...
Yes if there is a short to ground you won’t get a voltage reading. That circuit is designed to protect it’s self if there is a short to ground, although the protection isn’t 100% and occasionally will still damage it if repeatedly shorted to ground. Take the diagram that Ross posted and check for 5v one at a time at each sensor associated either the missing 5v. If you don’t get 5v, disconnect it and move on to the next one and repeat until they are all disconnected. If you don’t get 5v at any of them check at the pcm. If still no voltage, them I would consider cutting the wire to determine if there is 5v short to ground within the wiring harness. If still no 5v then the pcm is probably bad.
 
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