Start and die

[Justin101714]

I don't have a scan tool I could get one. Would that be signal from the ignition switch to the ecm.

No, as the crankshaft is turning, the reluctor wheel built onto the crankshaft has notches in it and the crank sensor picks up the gaps and provides the signal to the ECM to control ignition timing and injector pulse.

 

 

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[Lschmid]

Finally got scanner and plugged it in and it will not connect. Unable to establish communication.

So I hooked it to my truck scanner works .

[Lschmid]

OK I got an update. I have a spare ECM out of a parts tahoe the part # don't match I just wanted to see if scanner would connect and it did. I tried to start and it runs. ECM was the problem so I'm off to autozone reman flashed for $200. Dealer was $600

[2018GMC]

Glad you got it figured out. Thanks for posting the resolution.

[Motor City Rick]

Lschmid,

 

First, if the "Security Light is Flashing" in the "key on" position, your in a 10 minute fuel shutdown mode. Then it's the Passlock system. Not flashing, move on.

 

Second, what most people don't know, turn the key off, unplug one individual sensor at each test, starting with the MAF, if the motor stays running, replace the MAF, same goes for Crank, Cam, TPS sensors. Every "input sensor" has a "default setting" built within the ECM software to put the motor in a "limp in mode". Other car lines also have this feature.

 

Third, find a "node light" for your fuel injector electrical connecter, when you crank the motor, it should light once every engine revolution. No light, back track to see if all input sensors are giving data to the ECM. That is where a scan tool is needed.

 

You spent way more than if you went out and bought a scan tool that collects data. If you ever have to diagnose a motor malfunction, start with a good scan tool and understand the codes delivered. With the amount of stuff you touched I wouldn't be surprised if you didn't have 10 plus codes. When get a scan tool that collects data, record all the codes found, clear the codes, the crank the motor for 10 to 15 seconds. The new "hard codes" will be stored. Start with the first code listed and diagnose from there. It's gonna be something real simple.