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Pete
Pete, GMC Mechanic
Category: GMC
Satisfied Customers: 26353
Experience:  GM training and dealer tech for 14+ years. Diagnostics
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GMC serria 2500 HD: I just changed injectors on 02 lb7 and

Customer Question

I just changed injectors on 02 lb7 and while I reassembling the harness I notice I pulled the wires out of the FRP plug so I reconnected the wires with solder and butt connectors and I got a check engine light that said high rail pressure circuit. I switched the wires around on the plug thinking I had a couple in the wrong place and it did nothing. so I ordered a 03 harness from a used parts store and noticed it didn't have the 3 bar map sensor I needed. I also just noticed the bleeder screw on the fuel filter house wasn't tight. any ideas? ps the truck has a really bad lope and will sometimes die at idle. like its not returning fuel for the rail.
Submitted: 1 year ago.
Category: GMC
Expert:  Pete replied 1 year ago.
Hi,my name is ***** ***** I will be happy to try to assist you with this.I may need more information in some cases to help with answering your question.I apologize for any delay and I am posting as soon as I saw your question myself.
Is their fuel leaking past the fuel bleeder screw on the fuel filter housing?
If there is this will cause the injection pump to suck air and fuel and can cause the rail pressure code in some rare cases but will cause rough running or hard starting.It doesn't have to be a large leak causing this here just a slight leak where the injection pump is sucking air and fuel will cause this.I would start with repairing any fuel leaks and then re check the operation.
If the fuel rail pressure code comes back you will either have to repair the wiring correctly in the existing connector as it looks to be the 03 is different or obtain an 02 connector to resolve this here.Below are two links to pictures for the wiring colors in the connector for this sensor to make sure they are installed correctly.
https://www.dropbox.com/s/941l1lp0kv5h5ij/frp-05-19.gif?dl=0
https://www.dropbox.com/s/ppzesvsf3wf9m65/frp1-05-19.gif?dl=0
Thanks Pete