V1 Ark's City Goblin #187 (2008 SS/TC donor)

[Ark :D]

So the tan wire has continuity from the clutch sensor, to the fuel pump, and to pin 9 of ECM X2. Doesn't look like that's the issue.

I noticed that I have an oil light on on the cluster, even though I just changed the oil and the dipstick shows a full 5 quarts. Could a bad/missing oil pressure sensor prevent a proper crank?

I remember people having issues with the crankshaft position sensor. I double-checked mine and it seems to be plugged in. Being that I only had the engine's valve cover and timing chain cover off, is there any chance that the crankshaft position sensor is preventing a proper crank?

I am grasping at straws now, I know. Pretty soon I am going to feel inclined to not worry about my start condition and just build, build, build.

 

[Ross]

Did you reset the oil light after the oil change?

 

[Ark :D]

Hmm. I'd have guessed these cars would not have an oil life reading. Regardless, I have not done that, as my Info button does not exist yet. I'll have to remember to do this later, once I have the button panel.

 

[Briann1177]

Do these things in the fuse box without any cranking:

1. Pull the crank relay.
2. There should be one pin that is connected directly to ground and should read < 5 ohms.
3. There should be another pin that probably won't be a dead short, but should maybe be like 200 ohms to ground. This would be the purple wire.
4. There should be one pin that constantly has 12V on it.
5. Once you have those three pins mapped out, check the continuity of the final pin to ECM X2/57.

Take a picture of the fuse box, label what you see, and post it here.

 

[Ark :D]

Do these things in the fuse box without any cranking:

1. Pull the crank relay.
2. There should be one pin that is connected directly to ground and should read < 5 ohms.
3. There should be another pin that probably won't be a dead short, but should maybe be like 200 ohms to ground. This would be the purple wire.
4. There should be one pin that constantly has 12V on it.
5. Once you have those three pins mapped out, check the continuity of the final pin to ECM X2/57.

Take a picture of the fuse box, label what you see, and post it here.

Here goes nothin' ...

<5 ohm, ground .... green pin
~200 ohms, purple wire .... i cannot identify this pin. Again, my meter is not the greatest.
constant 12v .... yellow pin

(Consequently, yellow and green pins are the ones you short to crank the engine)

Since I can't identify the ~200 ohm, purple wire pin, I tested both remaining pins (top left, bottom right) for continuity to pin 57 on the ECM itself. Neither pin showed continuity.

Just to check myself, since I know I can be an idiot about this stuff ... I'm supposed to check continuity from the relay pin to the pin on the ECM, correct?

 

[Briann1177]

The wire that goes from the fuse box to the ECM is a straight wire. So from one of those two pins measured to the ECM location should be a dead short.
*EDIT* You need to measure to the female pin on the ECM wiring connector. If you have the ECM wiring connector off, there will be no continuity from the fuse box to the male pin on the ECM which won't be helpful.

I really don't know what resistance you should be seeing on your purple wire. I'd have to check mine.

 

[Briann1177]

Better yet, just unplug the purple wire from the start solenoid and measure resistance from the pin on the connector over to each of the two remaining pins on the fuse box side. One of them should be a dead short since you're basically just measuring a piece of wire with a fuse box connection in the middle.

 

[Ark :D]

To amend my last post, the top left relay pin has continuity with ECM X2/57.

The starter solenoid wire has continuity with the bottom left relay pin (green circle), which makes sense because when I jump that pin with the 12v relay pin, it cranks.

 

[Briann1177]

What about the bottom right pin? Should be a ground chassis ground connection. Apparently the start solenoid coil has a fairly low resistance. I really wasn't sure.

 

[Ark :D]

Ok, I spent the last 30 minutes educating myself on how 4-pin relays work. What had me super-confused was how the relay appears on the electrical diagram (and the mini-diagram on the side of the relay). I now understand that the two pins diagonal to one another will carry the voltage to the starter solenoid, while the opposite two pins will carry the control voltage.

Since I know the two pins that will carry the starter solenoid voltage, then I know the control pins. The pin that has continuity to ECM X2/57 should show voltage (12v? 5v? Something) when the key is at CRANK. The other control pin should be grounded.

So based on that clarity, I would expect to see the top left pin get voltage when the key is at CRANK, and the bottom right pin should be grounded.

The bottom right pin is NOT grounded.

The top left pin sees 12v at key ON, not only at key CRANK.

I don't think either of the bolded results are good. I believe I am finally understanding this now. My question is, where should the bottom right pin be getting its ground from?

 

[Ross]

To amend my last post, the top left relay pin has continuity with ECM X2/57. This is different than my LSJ, so GM changed this on the LNF.

The starter solenoid wire has continuity with the bottom left relay pin (green circle), which makes sense because when I jump that pin with the 12v relay pin, it cranks. Same as my LSJ.

The ECM must provide ground when it wants the engine to crank. The other side of this (on the relay) gets power if the clutch switch is pressed.

Have you tried wiggling and pulling on the key when in the crank position? That works for me... until I fix my ignition switch.

 

[Ark :D]

Deleted my last post ... need to think about this more.

 

[Briann1177]

The pins are diagonal to each other so that you can plug the relay in either way.

The bottom right pin needs to hook up to any ground point. You'll probably need to pull your fuse box apart and physically inspect X1/B12. Now, there is a fuse box ground that a lot of people forget about. If I disconnect mine, I know for a fact it won't crank. I don't remember exactly what pin it is, but it's definitely a problem child for a lot of builders.

*Edit* I think it's referred to as the headlight harness ground.

 

[Ross]

So based on that clarity, I would expect to see the top left pin get voltage when the key is at CRANK, and the bottom right pin should be grounded.

The bottom right pin is NOT grounded. This goes to ground when the ECM wants to crank the engine (on my LSJ). I think this wire goes to the ECM, not the top left... at least it is this way on my LSJ.

The top left pin sees 12v at key ON, not only at key CRANK. This is the same as my LSJ when the clutch is pressed.

I don't think either of the bolded results are good. I believe I am finally understanding this now. My question is, where should the bottom right pin be getting its ground from?

 

[Ross]

The pins are diagonal to each other so that you can plug the relay in either way.

The bottom right pin needs to hook up to any ground point. You'll probably need to pull your fuse box apart and physically inspect X1/B12. Now, there is a fuse box ground that a lot of people forget about. If I disconnect mine, I know for a fact it won't crank. I don't remember exactly what pin it is, but it's definitely a problem child for a lot of builders.

*Edit* I think it's referred to as the headlight harness ground.

The bottom right pin needs to go to ground is true... but it is the ECM that will pull this to ground when it decides to let the engine crank.

 

[Briann1177]

You're absolutely right about the ground connection, Ross. I knew there was a reason for the dashed ground lines on the schematic. That ground wire should tie back to the ECM on pins 1, 2, and 4.

 

[Briann1177]

Still make sure your headlight harness ground is hooked up though. Like I mentioned before, mine will absolutely NOT crank with it disconnected. I've tested that theory in the past just for fun to see if Lonny was BS'ing us or not.

 

[Ark :D]

I've confirmed that my bottom right pin gets grounded when the key is turned to CRANK. However, it only did so on the first attempt. I wonder if there's a reason it won't go to ground on subsequent attempts?

My top left pin sees 12v regardless of the clutch position. I've already confirmed that the clutch sensor plug and brake sensor plug are not mixed up (clutch has tan, light green, and gray in it).

Checked the headlight ground (again!), it is definitely grounded.

 

[Ross]

My LSJ clutch switch has pink & yellow wires. I removed the cruise clutch switch. The pink gets 12V+ from the BCM, and the yellow sends power to the crank relay when the clutch is pressed.

 

[Ark :D]

I am thinking that I need someone with an LNF to test the CRNK relay pins so we can compare apples to apples. I don't think what I am seeing is right, but I also don't think it would directly compare to an LSJ.

So, if someone with an LNF could check what they see at the relay, that would be helpful.

On the RED circled pin, do you only see voltage at key ON with the clutch pushed in?

On the BLUE circled pin, do you see ground while the key is at CRANK position?