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Discussion Starter · #1 ·
2005 Cobalt 2.2

Just removed, rebuilt, and replaced engine. Primed it and all was ready to start but all I get is cranking.

Injector Harness has voltage (5V and 12V) and ground. However no injector pulse. I believe that it is triggered by the crankshaft position sensor through the ECM so I next verified voltage at sensor. I was surprised to find 2.5V on both sides of the connector instead of 5V on one side.

I am more comfortable doing engine mechanical than electrical but I believe having the voltage split like that indicates a missing ground on that circuit. That correct?

I verified continuity from connector all the way to the ECM pin. Also verified wires are in perfect condition.

Does anyone know what would cause the ECM to provide power to both sides of that circuit? Where do I look? Am I on the right track?

I examined the wiring harness extensively looking for any issue. Engine replacement went well and had no pinched wires or any issues. All ground wires are connected and clean. I see none missing.

Thanks in advance for any ideas.
 

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You know the crankshaft position sensor is a Hall effect sensor and produces a low current pulse that a transistor picks up and amplifies. Search for how to test a Hall effect sensor
 

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Discussion Starter · #3 ·
When I followed the troubleshooting steps I learned it should have a 5V signal on one side and no voltage on the other. The guide I was following advised to tackle that before more testing could be conducted.

If my info isn't correct please advise.

If I have that voltage value split (2.5 on each side) that indicates an open/missing ground on that circuit. Correct?
 

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Discussion Starter · #5 ·
I don't need to test my sensor. I know it's good. The issue I have is instead of the 5V reference signal on one side of the circuit, it is split to 2.5V per side. That means a ground that is missing. I cannot find it. I was hoping someone on here possibly knew the ground routing that would cause this.
 

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Discussion Starter · #7 ·
Yes all grounds are in place. However the ECM seems to have an "open" ground in it allowing voltage on both sides of the circuit. I don't know what would cause this.
 

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Discussion Starter · #8 ·
The 2.5V on each side makes me think a missed ground. That on no way means that what it is. I do engine mechanical and rebuild engines. Electrical is not my jam and I woefully ignorant on most issues. My research says that a split voltage load can indicate an open ground. But I am sure it could me one of several other reasons also.
 

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2005 Cobalt 2.2

Just removed, rebuilt, and replaced engine. Primed it and all was ready to start but all I get is cranking.

Injector Harness has voltage (5V and 12V) and ground. However no injector pulse. I believe that it is triggered by the crankshaft position sensor through the ECM so I next verified voltage at sensor. I was surprised to find 2.5V on both sides of the connector instead of 5V on one side.

I am more comfortable doing engine mechanical than electrical but I believe having the voltage split like that indicates a missing ground on that circuit. That correct?

I verified continuity from connector all the way to the ECM pin. Also verified wires are in perfect condition.

Does anyone know what would cause the ECM to provide power to both sides of that circuit? Where do I look? Am I on the right track?

I examined the wiring harness extensively looking for any issue. Engine replacement went well and had no pinched wires or any issues. All ground wires are connected and clean. I see none missing.

Thanks in advance for any ideas.
What? You didn't have enough things to aggravate you and decided to put more time and money into the most aggravating car (I've ever owned)? If I'd have known life was too good for you, I'd have agreed to stop by at 3:00 AM on random days, run around your house banging on the walls with a pan to scare you half to death and then hose you down with ice cold water and run away! Maybe slam your head in a door or two just for a little pain!
 

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Did you search here on the forum for ground locations? There are posts showing almost every ground on your way Cobalt
I just replaced my clutch. As I was putting everything back. I wasn't sure which wire that was bolted to the transmission block as a ground and which was bolted to where? I know top center bolt had a wire. Then moving counter clockwise there's a threaded bolt with two wires separated with a nut. The third wire below that area went to the starter. If you can help correct the issue greatly appreciated.
 
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