Briann1177
Goblin Guru
J2, C2.
Ark's City Goblin #187 (2008 SS/TC donor)
- Thread starter Ark :D
- Start date
Briann1177
Goblin Guru
Ark :D
Goblin Guru
Thanks for the correction. I just re-checked, for my own sanity, that I have continuity between all five endpoints on the (green) low speed data, and continuity from end-to-end (OBDII through ECM) on the high speed data, as well as at each stop in between.
Still seems odd that I can't get an OBDII scanner to talk to the ECM, but that could easily be a function of my scanner or computer/phone.
I mean, this here is a mic drop. This is definitely (one of) the problem(s). I guess I have no choice but to just continue building the car until it is in a towable state, then deal with this later. Great find, and thank you.
Yep, just confirmed, all five have continuity.
Briann1177
Goblin Guru
I'm confident that you're going to be the first to do your first start inside a GM service department. That actually could work out to your advantage. 
Ark :D
Goblin Guru
So, per Ross's suggestion, I figured I'd crack the old broken TDM open and see what I was up against.
At first, I thought I wouldn't be able to get that board out, since it looks soldered to the coil and the five harness pins. But, looking closer, it looked like it may just slide over them. So, I worked at it a little with a flathead screwdriver and I managed to get the board out very easily.
I repeated the process in the other, undamaged TDM, and installed the new TDM with old guts back into the car. The key must be stored in the TDM, because the key that was "working" (a loose term) now was giving me the car security light on the cluster. So I swapped keys and cylinders back to the key that came with the donor, and my car security light now goes out as expected.
Still doesn't crank though.
At first, I thought I wouldn't be able to get that board out, since it looks soldered to the coil and the five harness pins. But, looking closer, it looked like it may just slide over them. So, I worked at it a little with a flathead screwdriver and I managed to get the board out very easily.
I repeated the process in the other, undamaged TDM, and installed the new TDM with old guts back into the car. The key must be stored in the TDM, because the key that was "working" (a loose term) now was giving me the car security light on the cluster. So I swapped keys and cylinders back to the key that came with the donor, and my car security light now goes out as expected.
Still doesn't crank though.
Briann1177
Goblin Guru
Try disconnecting your battery for like 10 minutes, and hook it back up.
And how are you hooking up your clutch sensor? Like mentioned before, it has to be in the precise position. You can't do it by hand thinking you're close enough.
And how are you hooking up your clutch sensor? Like mentioned before, it has to be in the precise position. You can't do it by hand thinking you're close enough.
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Ark :D
Goblin Guru
My car does not yet have wheels or shifter cables, so pop-starting it in 2nd gear isn't an option yet.
That being said, I tried shorting the RUN/CRNK relay, and no dice. I hear a click, but no crank.
My solenoid+ is not just a bare stud, it's a 1-pin connector with a thick rubber lip around it. So, rather than shorting it against the battery+ stud like in your pic, I ran a long wire from the positive pole on the battery and gave the solenoid+ pin 12v that way. CRANK! But no start. It turned the crankshaft, so I know for a fact now that my starter is good.
So then just to verify what I was thinking, I ran a lead from the solenoid+ connector (not from the starter, but from the wiring), put my meter in 20V mode, and tested for voltage while turning the key to crank position. Nothing ... confirming that whatever is going on, the car is not sending 12v to the starter when I turn the key.
It could very easily be the clutch position sensor. I still have yet to get the broken screw out of the original one, I just can't break it loose, even with heat. There's so little to grab onto with anything.
Either way, progress is still being made. Tomorrow I pick up my misc. powder coat items, and keep building the suspension to get the car on all fours and towable.
Briann1177
Goblin Guru
Is your fuel pump still not priming? I dont think an out of position clutch sensor will make it not prime.
Ark :D
Goblin Guru
Correct, fuel pump is still not priming. Not that I can hear, anyway.
Briann1177
Goblin Guru
You'll definitely hear it prime. Can you post a video of the dash lights in both run and run/crank positions?
Briann1177
Goblin Guru
I see two issues. The first is no check engine light, but that might be because you might not have the brown MIL wire hooked up for your gauge cluster. Probably not too big of a deal. The other and more concerning issue is the power steering message. I hate to beat a dead horse, but that indicates a high speed GMLAN issue.
I'm not sure if the PS unit needs to be powered, but is everything plugged in? You should have a power connector and another connector that has two wires for GMLAN in and two wires for GMLAN out. The GMLAN is a serial bus so if there are any breaks, things won't work. I also don't think you can do an end-to-end resistance check. I'm pretty sure you'll need to test each link in the chain. So OBD-II --> Power Steering --> BCM --> ECM.
I'm not sure if the PS unit needs to be powered, but is everything plugged in? You should have a power connector and another connector that has two wires for GMLAN in and two wires for GMLAN out. The GMLAN is a serial bus so if there are any breaks, things won't work. I also don't think you can do an end-to-end resistance check. I'm pretty sure you'll need to test each link in the chain. So OBD-II --> Power Steering --> BCM --> ECM.
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Briann1177
Goblin Guru
On a side note, the gauge lights and driver information center are doing what they're supposed to do. They go off when you crank and come back on in run mode.
Ark :D
Goblin Guru
This behavior is what I've always seen in all my cars. However, all I've ever driven is Fords, so for all I knew, Chevy is different. I knew a keen eye here would point it out if it was a problem; I'm glad it's not.
I don't remember seeing anything about a brown MIL wire for the gauge cluster. I'll have to go back and re-watch the new wiring video series.
The power steering message bothers me, because in addition to what you said ("GMLAN issue"), my OBDII scanner cannot connect to my ECM. First of all, everything is definitely plugged into the power steering unit. Thinking I might have a bad unit, I went out to the garage to swap them. I swore I had the one from my original donor, but I must have sent it to someone to help them out, or trashed it with one of the donor shells. So I decided to try two things.
I unplugged the power connector, turned the key on, and tested for voltage. I saw the expected 12v on my multimeter.
Second, I thought I'd be slick and try to bypass the power steering unit in the high speed data circuit entirely, by looping the pins in the PS connector. It did not work, my scanner still could not see my ECM.
ctuinstra
Goblin Guru
I'm with Brian on this one. As soon as I seen the POWER STEERING message I had flashback to when I locked up my ECM with HP Tuners. It acted the exact same way! No crank and no start. No communication. You can troubleshoot starters and relays, etc all you want but that ECM or BCM is not going to allow that engine to run.
ctuinstra
Goblin Guru
If your scanner s not reading anything on the data lines, something is wrong there and that's what you need to forum on. I know I sound like a broken record, but makes sure you have good grounds, especially on the grounds to the ECM.
Side note, I've seen articles that with only 4-5 wire to the ECM and HP Tuners can communicate with it and read/write. Positive, ground, TX, RX, and something else. Point being, there is not a lot required to be correct to be able to read data.
Side note, I've seen articles that with only 4-5 wire to the ECM and HP Tuners can communicate with it and read/write. Positive, ground, TX, RX, and something else. Point being, there is not a lot required to be correct to be able to read data.