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Discussion Starter · #1 ·
Sorry, I feel like a broken record here coming to inquire about my problems. This will be a bit long-winded, but I'll try to keep it as succinct as possible.

Here goes:

Pre-pandemic, I was dealing with a persistent issue with the car going into Safety Mode and cutting power. In an attempt to remedy this, I changed:

1. Gas pedal sensor
2. Throttle Body
3. Throttle Body Pigtail

The car did run properly for quite a while until the problem would randomly pop up again and then subside. Switching back to the old TB, the problem would pop up every single time the car would go about ~3,500RPM, so that seemingly seemed to be part of the problem.

Fast forward to a couple of months ago. I replaced the battery as well as the battery terminals with OEM Delco ones. All connections were secured. Upon starting the car, the coolant temp didn't work and the secret menu had the temp pegged at some astronomical number that I forget, even when cold. The problem randomly went away one day after a few drive cycles. Since then, the car has worked flawlessly for ~700 miles with a lot of normal commuting mixed with some spirited highway blasts mixed in.

A couple of days ago, I was driving the car to work. Every time the Safety Mode issue has cropped up, I've noticed that I can feel power being cut at some point in the RPM range. Well, merging onto the highway, I thought I felt it a bit. Car was still warming up, so I didn't take it past 3,000RPM and started to cruise at ~65MPH. I got about 3 miles holding steady speed and RPM and suddenly the car kicked into Safety Mode. Anyone who has had this happen know it sucks on the highway. I floored the pedal and the car still started to slow down as I managed to merge into the next exit which thankfully had a rest area which I pulled straight into and the car promptly died. I popped the hood and looked to see if anything had maybe popped loose. I couldn't see anything apparent, so I gave it a minute and started the car back up ... horribly rough idle, immediately shut the car off. Went back under the hood to no avail at spotting anything. Turn it on again, and the idle is still terrible. Shut it off. Cross my fingers, wait 15-20secs and try again ... car idles perfectly fine. I ease it back onto the highway and get the car to work. When I hit local streets, I notice the car is idling high @ ~1,100RPM, but otherwise runs smooth. Get it to work, shut her off.

~12hrs later, I finish work and go to start the car. click Nothing. It was a very faint click ... not like the kind you'd hear from there being low power from the battery. I don't know what it was honestly. Turn the key off and pull it out. Re-insert it and start it ... this time it roars to life but the idle is terrible again, even worse than before. Off. Shake my head as my co-workers look at me wondering WTF is wrong with my car. Start it again and thankfully it starts up "normally." I make the drive home, noticing that the car will sometimes idle high, sometimes it will idle normal.

CEL turned on, checked the codes:

P0171 Bank 1 Lean
P0174 Bank 2 Lean (AF gauge reads normal)
P2135 TPS Sensor A/B Correlation (it's been changed twice now in 56k miles)
P2176 TAC System Idle Position Not Learned
U0001 High Speed CAN Bus

Mods are:
Built Shortblock with forged internals (dished pistons to lower compression)
Maggie 122 supercharger
LPE GT2-3 cam
Full Exhaust with L/T ARH headers
LPE CAI

I also have a LPE MAF, could it be going bad? The fact that not a single code comes back to the MAF though makes me think against it. Another possibility I was thinking of was the ECU being bad, as I hear that can be an issue with 2005 GTO's (which mine is).

I found this company which is actually local to me: https://www.fs1inc.com/2005-pontiac-gto-6-0l-pcm-engine-computer-ecm-ecu-programmed-plug-play.html

Anyone heard of them? What else would I need outside of having them re-furbish the ECU to get the car to work? I don't even know if I want to deal with the car anymore though. After spending $1,000 on trying to get the car to run properly, dropping another $750+ on a possibility isn't looking too appeasing. I love the car, but it may just be time to let go.

Appreciate any feedback.

PS: Oh, almost forgot. I don't know if this is a sign of anything, but when I went to read codes with my OBDII scanner, when the vehicle went to do the system check, every warning light came on and every warning was going thru the center display. ABS fault, service engine soon, fuel gauge error, etc. Unplug it and all the warnings went away. I had to play with the connection to the point where it wasn't seated too far in, but it was deep enough to actually connect with the scan tool. I checked with another one of my cars, and it connected without issue, so it's not the scan tool. Dunno if that's a sign of anything, but it may be pertinent to something?
 

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The obd2 connection does that sometimes depending on when you plug the scanner in (key position)
 

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Discussion Starter · #4 ·
The obd2 connection does that sometimes depending on when you plug the scanner in (key position)
Tried it. Started with the car completely off, connected the scantool and then turned it to accessory mode. No dice. Tried it while power on and system check was going, same thing. I did it after all the system checks came back good, and once I connected the tool, it would trigger all the warnings. Multiple tries with each.

Sounds to me like you've got a short circuit somewhere or a fubar-ed ECU. But how to figure out what and where?
I would very much agree. The fact that my old TB will trigger Safety Mode immediately upon going over 3,500RPM though, while the new one it's very intermittent ... would that mean it's more likely one or the other? Or completely unrelated?
 

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Discussion Starter · #5 ·
So, found this on the YouTubes ...


You can start the video ~2:45. Is this a good way to check for a short to ground? The video has a lot of Likes, but a substantial about of Dislikes as well. Yay or nay? I checked my car just now using this method and found the draw to hover around 0.5amps, which he says is within the normal range. Is this enough to rule out a short and make the issue likely compooter related?
 

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I would very much agree. The fact that my old TB will trigger Safety Mode immediately upon going over 3,500RPM though, while the new one it's very intermittent ... would that mean it's more likely one or the other? Or completely unrelated?
i almost want to say that feels like an airflow problem, but it would throw different codes. MAF/MAP correlation.

can you trigger the error sitting free revving the engine or with the engine off?
 

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if you test the throttle body or pedal sensor circuits, they are all direct between the ecm and throttle body or sensor. the ECM provides 5v reference and ground, and then there are the signal wires.

as far as the lean codes, maybe start with a vcmscanner log if you have hptuners. look at the o2 sensor response, and the fuel trims. your wideband may hover around 14.6 but that's only after your fuel trims have corrected significantly.
 

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Discussion Starter · #8 ·
i almost want to say that feels like an airflow problem, but it would throw different codes. MAF/MAP correlation.

can you trigger the error sitting free revving the engine or with the engine off?
With the old TB, yes, it will trigger to safe mode with the car free-revving. With the new TB, I don't think it will, but I haven't tried. It's so intermittent with the new TB whereas the old one it was happening every single time it revved over a certain RPM. Literally put the old one back one, felt it start to cut power and then it went into safe mode the very first time it went past that RPM. Put the new one back, no issues doing multiple WOT pulls. Old one, instantly has the issue again ... new one, back to running perfectly. Of course, now I have a problem with even the new one, but I was cruising at ~65MPH in 6th, so that would be, what, 2,000RPM when it triggered?
 

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The fact that plugging in the scantool causes all of the codes to show up makes it sound to me like there is a short somewhere on the CAN bus wires. Weird why plugging in the scantool would cause the short to appear though. But that along with the High Speed CAN bus fault is definitely making me lean toward saying it is either an intermittent CAN Bus short or an ECU problem. That fact that it is intermittent definitely makes it sound like it is NOT a hardware issue.

Check the resistance between pins 6 and 14 on the OBD-II port with a voltmeter. I believe it should be 120 ohms - though it might always be normal except when you are having the problem or just for a split second when the problem is triggered. Would be good if you can also pierce the cable and check resistance there with the scantool connected. It should still be 120 ohms. Maybe try to fiddle with the wires or pins to see if you can get them to show short..

last thought/edit..
have you checked the infamous wiring harness behind the glove box for potential wear causing electrical shorts?
 

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You need to check all of your sensor connections for
1) corrosion
2) pins or connectors pushed back within the plastic plug.

every. single. plug. you unplugged when swapping the engine. make sure the wire(s) arent pinched between the trans bellhousing and engine.
 

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any malfunction module on the can bus can cause issues. the datalink connector has direct connections to the PIM for canbus and UART, UART to the BCM, and older serial protocol to the EBCM for abs stuff.

fyi not all the modules talk over canbus. the PIM is the last stop before data is converted for canbus for the datalink connection. ECM, TCM, and EBCM are canbus, i think. a lot of the other modules use other serial protocols.
 

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Check your coolant connector first. It’s in the front of the engine on the driver side in front of the exhaust ports. I had an intermittent problem with mine where it would idle real rough. Sometimes the temp gauge would immediately peg out. Then it would straighten out. Then one day it got worse to the point where it wouldn’t stay running. I bought a new pigtail, cut the old plug off and put a new one. Never had an issue again. It was corroded inside the female connectors.
 

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Discussion Starter · #13 ·
Coolant temperature sensor appears to be ok. No visible corrosion at the connectors or anywhere else.

At the suggestion of luggage via PM, I checked the BCM wires behind the glovebox today. I never knew this was a common issue. So, of course, my luck, the cloth tape is barely rubbed through to the point where I need to pull it way back and finger the area to see that any wires were visible. The plastic covering on the wires is entirely intact with zero signs of wear. I'll still wrap the wires with some rubber tubing as a precaution, but it doesn't look like it's from there.

I did find something that sounded some alarm bells. The wiring going into the top connector of the ECU was exposed as the tape really wasn't doing its job anymore, despite still being in place ... it was loose and actually split when I pulled it back. Upon pulling it back, I noticed this brown with red stripe wire completely exposed. Not only is it exposed, but part of the wire is actually broken. There was also some weird oily residue on it for some reason. I have no idea what it is. It's golden, but doesn't seem like motor oil ... it was a little tacky and not completely slick like most lubricant oils. It looks like only one strand is broken. Do you guys think I need to solder this (will have to look up how to do it)? I tried to get the camera to focus on that specific wire, but it just wouldn't ...

Black Space bar Office supplies Office equipment Bumper


From how dirty the wire loom is, you can see that the tape had failed and was letting plenty of dirt in. I don't know how that brown/red wire would have gotten completely exposed like that though (only part of it was eaten away, the opposite side of the protective sleeve is still there but I turned the wire to show the exposed part). Possible culprit found?
 

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Can you figure out what pin number that exposed wire goes to? There are wiring diagrams I've seen in other threads that should then be able to tell you what that goes to and if it could be the source of your problem.
 
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