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Everything electronic is dead, where do I start?

679 Views 5 Replies 4 Participants Last post by  SvdSinner
In my continuing saga of my "3 day repair" on my CTS (getting close to week 11 :(), I finished installing the new engine, reconnected the negative battery terminal to the battery, and was going to try to do a first start. However, the remote did not unlock the doors, and when I used the physical key to get inside, it still acted as though my battery was disconnected. The "key" wouldn't turn at all, and nothing I tried was operational. I check the battery, it was full. I checked the positive terminal in the engine bay and it is showing 12V.

So, I can think of 6 possibilities:
1) I somehow have some really important connector either disconnected or loosely connected so that no contact is made. Obviously while replacing the engine, I disconnected and reconnected just about everything on the wire harness, plus the engine block to body ground wire.
2) I blew some sort of master fuse. I couldn't find anything in the engine bay fuse box, nor could I see any fuse labels that seemed like they might be capable of causing such an issue. I haven't checked the rear fuse-box yet, since my assumptions are that: A) Since power is making it to the engine bay, there isn't a master fuse in the rear that is blown. B) Everything I've touched is in the engine bay, except for the negative battery cable.
3) The main computer is fried.
4) There is some immobilizer feature that needs to be reset after everything has been disconnected/reconnected.
5) After being disconnected for a couple weeks, the car has forgotten my key-fob and won't turn on. (Although I'm pretty sure that it would show me something on the dashboard display if the key fob wasn't detected.)
6) A problem with the fake ignition key that has it locked in the off position. (It doesn't turn at all, and I don't know if that is normal with all the electronics off.

Details that might matter:
  1. I didn't remember to disconnect the negative battery terminal at first, so there are a few hours I could have fried things
  2. When pulling the starter motor, I accidentally touched the positive wire to the frame and got a big spark. (This is what reminded me to disconnect the battery)
  3. I did pull the ECU out of the car before #2 happened, so it was safe from that big spark. This obviously assumes I hadn't unknowingly did something else less dramatic to kill it before I pulled it out of the car.
  4. I am aware of 5 points where the engine/harness is grounded and that I have checked: Passenger side head grounded to harness, Passenger side of engine block to passenger strut tower, passenger-side harness to body, a few inches below the fuse box, and driver side harness to driver side head. If I somehow missed a ground, that could be a culprit.
  5. I had a few things not connected yet: the windshield wiper motor, the front bumper, the driver side headlight, and have one two-prong plug on the driver's side rear that I can't figure out what it goes to. I don't think any of that should prevent the car from starting, but I haven't found anything authoritative on what the minimum amount of things to plug in to allow basic functionality is.
  6. I wasn't super-thorough checking for things that didn't work. If the ECU is somehow completely dead, are there things I should expect to work? (I was a bit too frustrated to think logical when nothing worked.)
Where do I start to troubleshoot what is preventing everything from working? How do I know if the ECU is dead or if something else is the culprit?
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Is this a keyless or keyed-entry vehicle?

I know with keyless, there is a slot in the center armrest to insert your key fob when power is low (in the fob) and you need to start the vehicle. I'm not sure if this carries over to the keyed version but it's worth trying if the slot is there. To be clear, I'm fairly certain you need the key fob inserted still containing the key blade for this to properly work.
After hunting through the fuse box for any blown fuses, it finally occurred to me to test the 12V bar going into the fuse box. (I had previously been testing the terminal where the battery positive connects to the bar that goes to the fuse box.) Nothing. I check the continuity between the cable from the battery and the fuse box. Nothing. I grab a 13mm wrench and see how tight the bolt is. It wasn't tight. Tighten, tighten, tighten. Suddenly everything I had been turning on to test came to life, including the car alarm. It was solved. I grabbed the key fob, hit "unlock" and the alarm silenced!

Then I tried to do a first start of the new engine. Not as good. She cranked for 10-15 seconds, fired up, and died with a big puff of smoke from the engine compartment. (Not entirely unexpected or necessarily bad. I don't have the exhaust fully hooked up on the driver's side and not all of the PCV tubes are on the engine.) Further attempts consistently gave an immediate fire up for 1-2 seconds and dying with more smoke. The engine doesn't sputter at all, just dies cleanly like the ECU told it to.

I'm currently letting my BlueDriver do a full scan to see what codes might be causing the engine to stop. Back to my engine replacement thread!
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Good find.
Hopefully your lucky streak continues with your new engine!
hook the pcv lines back up. You are sucking in way too much unmeasured air. Do not just plug them off or you will blow seals out on your car. They are there to vent the excess pressure but will allow air to be pulled in. My car with one of the lines partially dislodged was having popping coming out of the intake.

If the exhaust is not hooked up the o2 sensors can't work either. Probably won't be an issue until the car comes up to temp. But I would suspect your car will die once it comes upto temp since it can not adjust your fuel to air ratio.
hook the pcv lines back up. You are sucking in way too much unmeasured air. Do not just plug them off or you will blow seals out on your car. They are there to vent the excess pressure but will allow air to be pulled in. My car with one of the lines partially dislodged was having popping coming out of the intake.
Just noticed I never followed up on this. It absolutely was an issue with sucking in too much air, but for a different reason. I had (embarassingly) installed the intake manifold without the gasket which was causing it suck in tons of air. (I guess I got sloppy after installing/reinstalling the intake 15+ times across all the work/troubleshooting I did on the engine. Fixing that (and reinstalling the wiring harness on the fuel rail pressure sensor, but that was another issue) got everything running.
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