No Pulse to injectors

Tiny
JT1783
  • MEMBER
  • 2006 CHEVROLET SILVERADO
  • 4.3L
  • V6
  • 4WD
  • MANUAL
  • 250,000 MILES
X VIN code, replaced head gaskets a few months ago and after reassembly the engine would not start. It will run if I spray carb cleaner into the intake, but the second I stop, the engine shuts off. I have 12v at injectors but am not getting a ground pulse while cranking. I replaced the ICM ( before the head gaskets due to a no spark problem when I bought the truck), distributor assembly and ecm. Fuel pressure is around 57-60 psi, which is a little low from what I've read. Compression on all cylinders is around 160 PSI. The only code that's showing is a maf low volts that it had since it was running. Not sure what to check next.
Sunday, July 18th, 2021 AT 1:47 PM

11 Replies

Tiny
ASEMASTER6371
  • MECHANIC
  • 52,796 POSTS
Good evening,

Did you have the ECM programmed to your VIN number?

When you crank the engine, does the tachometer read RPM? That will tell me if the crank sensor is working. If it is not, the ECM will not pulse the injectors.

https://www.2carpros.com/articles/how-a-crank-shaft-angle-sensor-works

If the signal is there and the ECM is programmed, then you have a wiring harness issue between the injectors and the ECM.

https://www.2carpros.com/articles/how-to-check-wiring

https://www.2carpros.com/articles/how-to-use-a-voltmeter

I attached a wiring diagram of the system for you. I highlighted the wires that go to the ECM for grounding.

Roy
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Sunday, July 18th, 2021 AT 4:33 PM
Tiny
SQM
  • MECHANIC
  • 6,383 POSTS
Hello,

The fuel pressure range for your Silverado is 55-62 PSI (key on, engine off), so the pressure is where it should be.
It is good chance that there is a issue with wiring somewhere in the circuit.
I have attached wiring diagrams as well as some diagnostics for your fuel injectors.

https://www.2carpros.com/articles/how-to-check-wiring
https://www.2carpros.com/articles/how-to-use-a-voltmeter

Let me know if you have any questions.

Thank you.
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Sunday, July 18th, 2021 AT 4:41 PM
Tiny
JT1783
  • MEMBER
  • 5 POSTS
Thank you for the replies, the ecm was programed to my VIN and I did the passlock relearn. When cranking the tachometer does not read rRPMs, but if the engine is running on carburetor cleaner it reads around 1,000 RPMs. I checked the ground wires for continuity quick, and I do have continuity from the injectors to the ECM. I will try and do a more in depth check on the wires after work tomorrow, I will update as soon as I can.
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Sunday, July 18th, 2021 AT 5:14 PM
Tiny
SQM
  • MECHANIC
  • 6,383 POSTS
That sounds good. Let me know any way if I can help. Thanks.
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Sunday, July 18th, 2021 AT 5:25 PM
Tiny
ASEMASTER6371
  • MECHANIC
  • 52,796 POSTS
If that is true and the wiring is good to the ECM, you may have a bad ECM. Make sure there is power from the injectors to the ECM. If you have power, then your new ECM may be the issue.

Roy
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Sunday, July 18th, 2021 AT 5:28 PM
Tiny
JT1783
  • MEMBER
  • 5 POSTS
Okay, I didn't have much time after work, but here's what I got:
Battery voltage is 12.74. Volts at crank sensor is 11.74, volts at injectors are all 12.69. Volts at cam sensor is 11.79 and at ICM 12.7.
Key on but not cranking injector control wires have continuity to ground and all control wires have around 12.28 volts at ECM.
All 3 crank sensor wires have continuity to ECM.
Also got a new code from the ECM, code 315, says crank position not learned.
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Monday, July 19th, 2021 AT 2:56 PM
Tiny
ASEMASTER6371
  • MECHANIC
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Okay, good information.

If you have 12.28 volts at the ECM, then good chance the ECM is the issue. The wires should not be grounded cranking. There should be a pulsed voltage depending on which cylinder is commanded to be allowing fuel.

The crank sensor relearn needs to be done once you get the motor running. It is a procedure for the sensor that must be done. It should still run even when not relearned.

I posted the procedure below.

Roy
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Monday, July 19th, 2021 AT 3:32 PM
Tiny
JT1783
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  • 5 POSTS
Okay, so I need a new, new ECM. Is there a company I can get one from you recommend? I'm definitely not going back to the one I got this one from.
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Monday, July 19th, 2021 AT 3:47 PM
Tiny
ASEMASTER6371
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That should be covered under warranty since you just replaced it.

I would suggest the dealer. It is more expensive but well worth it.

Roy
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Monday, July 19th, 2021 AT 3:58 PM
Tiny
JT1783
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  • 5 POSTS
Okay, I contacted the company about getting the ECM exchanged. I'll update as soon as I get a new one. It took them 3 weeks to get me the first one, so it may be awhile.
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Tuesday, July 20th, 2021 AT 3:01 PM
Tiny
ASEMASTER6371
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No problem. We will be here for you when you can continue.

Roy
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Tuesday, July 20th, 2021 AT 3:04 PM

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