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Ask GM Tech (Cam) Your Own Question
GM Tech (Cam)
GM Tech (Cam), Chevy Technician
Category: Chevy
Satisfied Customers: 15201
Experience:  GM Grand Master Technician 2007. 14 years experience.
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2007 Impala 3.9 No crank Possibly a can issue No

Customer Question

2007 Impala 3.9
No crank
Possibly a can issue
No communication with bcm and ecu
Submitted: 1 year ago.
Category: Chevy
Expert:  GM Tech (Cam) replied 1 year ago.

Hi there, I am Cam. Can I get your first name please?

Is the check engine light on?

What is the recent history up to his issue?

Customer: replied 1 year ago.
Jason
Check engine light comes on with key forward
When turning ignition to start-nothing
Can not communicate with-bcm or ecu with my scanner
Customer: replied 1 year ago.
Bought car at auction
Not sure on past history
Expert:  GM Tech (Cam) replied 1 year ago.

Ok Jason, this will be difficult then without history. For now, what type of scanner do you have?

Does it look like any aftermarket devices are installed?

Customer: replied 1 year ago.
Snap on scanner
Nothing aftermarket installed
Expert:  GM Tech (Cam) replied 1 year ago.

With a meter, measure resistance at that data plug. 200 ohm range, pins 6 and 14, pin layout is top left to right, 1-8, bottom left to right 9-14. Key off. What is the resistance?

Customer: replied 1 year ago.
Nothing
No resistance
Customer: replied 1 year ago.
I have power 12v on pin 14
Expert:  GM Tech (Cam) replied 1 year ago.

Sorry bottom row is 9-16 not 14. Please check again.

Customer: replied 1 year ago.
I have 12v on 16
Pin 6 and 14 goes to 000 with meter on 200k
Expert:  GM Tech (Cam) replied 1 year ago.

200 ohm range, not 200K, ideally we are looking for 60 ohms but it could be 120 or 0.

Customer: replied 1 year ago.
01.3 on 200 setting
Expert:  GM Tech (Cam) replied 1 year ago.

OK so your data line is shorted together. This is going to be a pain. These wires are the data line, twisted pair tan and tan black that run to each module. How are you with reading schematics?

Customer: replied 1 year ago.
Very basic
But have managed in the past
Expert:  GM Tech (Cam) replied 1 year ago.

OK so with the schematic, start plugging the modules till you get resistances like I mentioned then look at the wiring between the last one you unplugged and the next one in line.

Customer: replied 1 year ago.
I'm still here
Wiring checks out
When ebc module is unplugged I get 120 at data link connect
When connected (ebc)I get 1.5
I have 120 on both sides of the ebc module
It appears ebc is causing communication problem?
Customer: replied 1 year ago.
Which ebc unplugged I'm getting 120 on the bcm side and 120 on the TCM ecm sidr
Expert:  GM Tech (Cam) replied 1 year ago.

You mean the EBCM for the brakes?

Expert:  GM Tech (Cam) replied 1 year ago.

IF so that is great diagnostics. That means your EBCM is faulty, internally shorted and causing this. Myself I would try manually connecting the tan to tan, and tan black to tan black over the EBCM connector and see if it starts.