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Check engine light on, code P0256

Tiny
HD2424
  • MEMBER
  • 2005 GMC ENVOY
  • V6
  • 2WD
  • AUTOMATIC
  • 165,900 MILES
I was driving home, and the A/C wasn’t working too good. I had a check engine light turn on with p0256. It started to overheat, I pulled over immediately. Could it possibly be the fan clutch? Please provide how I should proceed.

Thanks
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Tuesday, April 5th, 2022 AT 3:00 PM

7 Replies

Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 42,883 POSTS
This sounds like two separate problems, the code P0256 Injection Pump Fuel Metering Control B Malfunction (Cam/Rotor/Injector) which I have seen the fuel pump that is going out can cause the issue because the computer can control the fuel pressure but to be sure here is how to check the fuel pressure in general with specific instruction in the diagrams below. Please re-post the overheating and A/C issue which should be related.

https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator

Fuel Pressure (Key "on", Engine "off") .................... 345-395 kpa (50-57 psi)

Check out the diagrams (below). Let us know what happens and please upload pictures or videos of the problem.
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Wednesday, April 6th, 2022 AT 10:19 AM
Tiny
KEN L
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  • 42,883 POSTS
Here is how you can change the fuel pump out in general with a guide below to show you how on your car:

https://www.2carpros.com/articles/how-to-replace-an-electric-fuel-pump

Check out the diagrams (below). Please let us know what happens.
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Wednesday, April 6th, 2022 AT 10:25 AM
Tiny
HD2424
  • MEMBER
  • 191 POSTS
Okay, will do. I got fan problem fixed, it was a bad relay.
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Wednesday, April 6th, 2022 AT 10:58 AM
Tiny
HD2424
  • MEMBER
  • 191 POSTS
I’ll be checking fuel pressure today.

Thanks for the help.
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Wednesday, April 6th, 2022 AT 10:58 AM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
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Nice work, let me know on the code P0256 problem.
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Wednesday, April 6th, 2022 AT 11:47 AM
Tiny
HD2424
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  • 191 POSTS
Will do.
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Wednesday, April 6th, 2022 AT 2:50 PM
Tiny
HD2424
  • MEMBER
  • 191 POSTS
Update: fuel pressure below spec got new fuel pump ordered. Thanks for the help.
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Thursday, April 7th, 2022 AT 5:46 AM

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