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Ron
Ron, ASE Certified Technician
Category: GMC
Satisfied Customers: 33477
Experience:  35 years in the Automotive repair business.
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My check engine light came on so I turned the truck off to

Customer Question

My check engine light came on so I turned the truck off to hook up my obd2 scanner to check for a code. It had come up with a P0118. I removed the obd2 plug and then started the truck. It started although it was running rough and after a minute or so it then died. At which I turned the key to the off position and tried to restart again. When doing so I noticed that with the key in the accessory position I noticed that the dash would not come on as normal and has not since. The truck will turn over even though the accessory dash lights don't come on but it will not start. I checked the fuses to see why the dash warning lights would not come on. It seems like there is a blown fuse, breaker or an open wire.
Submitted: 9 months ago.
Category: GMC
Customer: replied 9 months ago.
This is a 1996 GMC K1500 lwb extended cab.
Customer: replied 9 months ago.
With a 5.7 4x4
Expert:  Ron replied 9 months ago.

Hello, my name is ***** ***** I am a professional here at Just Answer. I have noticed that your question was not getting a response and thought I would see if you still need help with this.I apologize for the delay and I hope I can still assist you with this here.

There is only one fuse that will keep the engine from cranking and that is the #6 maxi fuse located in the under hood fuse panel. Start first with checking it to be sure its not blow. See the wiring diagram in the link below, copy and paste the link to your browser to open and view it.

https://dl.dropboxusercontent.com/u/104923897/No%20crank%20Feb%2022.pdf

Customer: replied 9 months ago.
Thank you for responding. The truck will turn over but when I turn the key to start all off the lights on the dash will no longer come. Plus... the truck starter will turn to start but it will not start.
Expert:  Ron replied 9 months ago.

Start first with making sure you battery is fully charged and the connections are clean and tight and if that checks okay, take your 12 volt test light and or a volt meter and with the key in the crank position check and see if you have power on both wires at the starter. Check this and post back with the results and we can work from there.

Customer: replied 9 months ago.
there is power - battery has been fully charged. It will turn over but will not start. When I turn the ignition key to the start position the radio will come on (Indicating that the key switch is sending 12v to the radio). But the indicator lights (air bag, check engine and whatever) will not light up as normal.
Expert:  Ron replied 9 months ago.

Have you had the computer system scanned to see if there are any fault codes setting?

Customer: replied 9 months ago.
No
Customer: replied 9 months ago.
I will try that next
Expert:  Ron replied 9 months ago.

Okay post back with the fault codes and we can work from there.

Customer: replied 9 months ago.
ok
Customer: replied 9 months ago.
I plugged the scanner in and pushed scan but it comes back with an error saying to plug the scanner in. I have used this scanner for many years and know from experience that the only time this error code comes up is when I plug the unit in and push scan without turning the key to accessory . But non the less I got another scanner to check and it shows the same. So that tells me that it is an electrical issue and that is why when I now turn the key to the accessory position I no longer get the normal dash lights that should come up before the truck is started. Also there is no power going to the ALDL when the key is turned to accessory.
Customer: replied 9 months ago.
I guess you are not able to help me, since it has been four days and you have yet to respond? Also... I have got a few request from you for me to leave feedback. I will definitely leave feedback once we solve this issue. So... lets move forward to solve this issue. Thanks
Expert:  Ron replied 9 months ago.

I had not received a response notice till today so I did not know you had responded back to me.

In most cases if your are not able to communicate with the scanner that indicates you may have a problem with the ECM (computer) . I have enclosed the steps to check it in the link below, copy and paste the link toy our browser to open and view it.

https://dl.dropboxusercontent.com/u/104923897/Scanner%20Com%20Mar%205.pdf

Customer: replied 9 months ago.
Why would you send some link you could have so easily typed or copied and pasted to the board. It's not like it had pictures or diagrams in it. When someone sends you a link to open, there can be hidden virus or such attached. So in the future please take the time to enter it yourself or put the whole address (URL - I think) down so we can copy the whole address and paste it our self.
Thank you
1. Verify power supplies to the PCM.
2. Verify the ground supplies to the PCM.
3. Verify the connection at the PCM.
4. If OK ground the Brown/White wire at pin 5 in the Black connector.
5. If the MIL now illuminates, replace the PCM.
6. The new PCM and programming is required
Customer: replied 9 months ago.
What are the steps to "VERIFY POWER SUPPLIES TO THE PCM" and "VERIFY THE GROUND SUPPLIE TO THE PCM"?
Expert:  Ron replied 9 months ago.

Ill open the post back up for you. Unfortunately I am not able to do the testing from here. Perhaps someone else can do this for you. Best to you and if they can help they will post back.

Customer: replied 9 months ago.
Close Question Tech Ron Was Unable To Help - Issue Solved.

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