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I think my ECM isnt communicating correctly with my starter…

Customer Question
I think my ECM...

I think my ECM isnt communicating correctly with my starter relay and engine. How would I troubleshoot this?

Mechanic's Assistant: How many miles are on the car? Has the car been starting normally?

186,000, it was starting normally up until the truck just wouldnt start out of no where. I replaced the batteries and the starter but to no avail

Mechanic's Assistant: What is the make/model/year of your car?

2003 GMC Sierra 2500HD, turbo diesel

Mechanic's Assistant: Are you fixing your Sierra 2500HD yourself? What have you tried so far?

Yes I'm fixing it myself, cant afford to get it towed to my local diesel shop. I replaced the battery, checked and cleaned the wires and connections. took out the starter and had it checked at my local shop, it passed, and now the only thing i can think of is it's the ignition switch or the ECM

Mechanic's Assistant: Anything else you want the mechanic to know before I connect you?

The engine light does not come one on the cluster when i turn the accesories on

Submitted: 1 year ago.Category: Car
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Answered in 13 minutes by:
3/21/2017
Auto Mechanic: Pete, Technician replied 1 year ago
Pete
Pete, Technician
Category: Car
Satisfied Customers: 32,138
Experience: 17 years automotive training and experience.
Verified

Hi my name is ***** ***** I will be happy to assist with this today.In some cases I may need more info to assist better.I apologize for any delay.

In your under hood fuse panel locate the starter relay.It should be a square relay.Tap on this relay while someone is trying to start your vehicle and see if it starts then.If it does then this relay needs replaced and is common for this issue.If this was already checked or replaced or if you need more info on where it is let me know.If tapping on it doesnt help with starting we can test the signals at this relay with a multi meter or test light to locate this fault just let me know.

If more help is needed, use the reply tab to continue our conversation. If no further assistance is needed, kindly rate my service,your 5 star rating is appreciated.You can rate at any time and we can continue to work on your question as this will not close out your question.Keep in mind in some cases it can be difficult to fully diagnose or help repair your vehicle without seeing it and I work on delivering the best possible answer from what I see to work with.

Thanks Pete

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Customer reply replied 1 year ago
When I turn my accessories on, my engine light doesn't come on like it's supposed to. Does that suggest it could be anything else ?
Auto Mechanic: Pete, Technician replied 1 year ago

Does the engine light come on briefly at all with the key all the way on?

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Customer reply replied 1 year ago
No, it does not come on at all. The anti-theft light comes on for a moment but then turns off though.
Auto Mechanic: Pete, Technician replied 1 year ago

I apologize for the delay.

If all other lights are coming on on the dash with the key on except the check engine light there is a good chance this is a faulty ECM here.To check this the power and ground signals will need tested at the ECM with a multi meter ( best option ) or a test light.If you have one of these to test with I may be able to tell you how to test this here just let me know.

Thanks Pete

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Pete
Pete, Technician
Category: Car
Satisfied Customers: 32,138
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Experience: 17 years automotive training and experience.

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