Viktimize

I'll give as much data as I can, but I'm up at work and don't have access to proper troubleshooting tools right now.

2004 Aveo. Just died while driving. Felt like the fuel pump died. Starter will engage and rotate the engine no problem. Checked all the usual stuff.

-30A Ignition fuse is good
-Cycled key a number of times, fuel pump will prime with key on every now and then(I assume it only primes if fuel pressure reading is low). But fuel pump does not run when trying to crank the engine.
-Confirmed timing belt was in tact.
-Pulled a spark plug, grounded to block and had a friend crank it over. There was no visible spark I could see.
-Swapped relays and checked fuses for fuel pump just to be sure about that. Everything is good on that end.

There's not many things that will completely cut out fuel and spark for cranking. Immediately I am thinking Crank position Sensor(CKS) or immobilizer.

Borrowed a cheap code reader from a friend in town that has Live Data. There's no codes stored. However I looked at RPM in the live data when cranking engine, AllData says it should read 200-300rpm when cranking. Live Data reads zero RPM. And the RPM gauge does not bounce or anything.

That seemed to point to an obvious CKS. Bought one and replaced it, still no luck. Exact same symptoms persist.

Started inspecting CKS harness and noticed it was touching the EGR valve. Pulled it away and found that the wire loom was melted through and the yellow signal wire was also melted through sheathing. Stripped everything off the harness, confirmed the wires are all still in tact. For now I wrapped electrical tape on the one wire that is bare to ensure it doesn't short out on anything. And taped the harness bundle back together. But it is missing the EMI shielding in that section for now. I'll repair it properly in the future, but I don't think this should have any effect on the ECM being able to read RPM to initiate a start. Could cause small RPM fluctuations leading to misfires when engine is running, but should not prevent ECM from seeing any RPM at all( Am I wrong about this?)

Unplugged harness from ECM. Used a Meter to check the harness for any shorts. No continuity between either of the 3 pins in the CKS connector, and no continuity with ground. Great, confirmed no harness shorts.

Plugged main harness back into ECM, and checked everything again.
-All 3 pins in CKS connector have continuity with ground now
-All 3 pins have continuity between eachother
-With Key ON, I get 2.5v on the yellow and blue wires, Nothing on ground obviously.

This is the part that has me convinced it is the ECM. I don't think there should be continuity across the pins or to ground on either of the signal wires. So I'm leaning towards the idea that when the yellow wire shorted to the EGR when it melted through, that it backfed something in the ECM and fried that circuit. Does anyone know for sure what these readings should be normally? It would only take 5 minutes to unplug your CKS and test the harness really quick to verify. Anyone able to confirm anything before I drop $500 on an ECM for this beater? Or if there's a way I can defeat the immobilizer without much difficulty in these cars, I'll just grab a used ECM at PickNPull. Any feedback is much appreciated.

I'll attach the wiring schematic and AllData Troubleshoot guide here if the forum allows it.

Viktimize

Even if I don't get any help here, I'll update along the way to a resolution in case anyone needs this information in the future.

Update.

Brought up a better code reader and a junk yard ECM. With a better reader I was seeing RPM on live data while cranking. Good news! Didn't need the junk yard ECM yet. Rather annoyed I spent a bunch of time going down the wrong road due to the cheap reader I borrowed not displaying live data correctly. But oh well, I repaired the melted harness I found while examining that circuit. I'm still a little leery on this circuit seeing as there is 2.5v signal voltage on both signal wires. I feel they should be 5v which is standard signal voltage from an ECM. But the ECM is seeing RPM, which is what's needed to run, so I'm not going to get lost down this rabbit hole for now.

This puts us at Step 5 of the Crank no Start Diagnosis. It appears to have no spark visually. Direction now is to move on to Electronic Ignition Diagnosis.



System check is done, it's just confirming that battery is properly charged and whatnot. So immediately go to step 4.

Both 30A Ignition fuses were confirmed good in the original post. But according to the schematic there is also a Fuse EF10 15A which is just for the ignition coil itself. Have to confirm that then on to Step 5.