Suburban wouldn't shift out of second gear temporarily

[South VA]

Well, that was a bust. The new ignition switch harness doesn't match the existing one. The existing one has two wires that come out of the large connector (with the 7mm bolt) under the dash, and go up above the steering column, presumably to another connector. I haven't been able to get to the top of the column to see where it goes, but it doesn't matter at this point; the harnesses don't match. I'm sending it back to Rockauto, but have been unable to locate a proper replacement. Not sure what to do at this point, except leave the original in place and work on the other variables.

 

[termite]

Check GM parts giant website using your VIN. It should give you the OE part number that you can cross reference.

 

[South VA]

Check GM parts giant website using your VIN. It should give you the OE part number that you can cross reference.

Thanks.

Just to make sure I wasn't missing something, I checked again. Turns out that I was looking at the two wires coming from one of the connectors on the side of the ignition switch connector.

The switch I have in hand appears to be the correct one.

I'm an idiot.

 

[South VA]

To wrap this thread up, here’s what I did:

Per @tayto ’s recommendation, I replaced the ignition switch and harness. Took awhile but I got ‘er done.

I discovered a couple of ground issues, discussed in my build thread (Link), and fixed them.

This is what happened:

After 300+ miles of test driving, there have been no further signs of hard shifting or being stuck in gear.

The charging system now seems to be working properly.



The acid test will be hauling the camper tomorrow to a campground a couple of hours away.

Also, I’ll leave my order with Jegs for the 2-3 ACDelco shift solenoid in place, and if it ever shows up, I’ll have a spare on hand if needed at some future point.

 

[South VA]

Well, the acid test did its job. Unfortunately it revealed that this vehicle is not quite there yet.

At first it wouldn't upshift from second, after which I pulled over and shut it off, then started it up again. It then shifted normally, until it didn't.

Trying to downshift from OD by accelerating resulted in it shifting quickly to second, then to third, where it remained for the next 20 miles. At least I didn't have to get it towed home.

It performed well on the way to the campground; the problem occurred soon after starting back home.

As I mentioned in my build thread, I'm stumped. There has to be something I'm missing here.

Edit: No codes, according to my inexpensive scanner.

Edit 2: So far it only happens when towing the camper.

 

[South VA]

I’m going to move this discussion to my build thread, to avoid further duplication.

LINK

 

[South VA]

In the interest of closing the loop on this thread (and in case you’re curious but don’t want to go through the build thread), I replaced the vehicle control module (VCM), which had an internal short; and the throttle position sensor (TPS), which was also faulty.

Problem solved.