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GM Tech (Cam)
GM Tech (Cam), Chevy Technician
Category: Chevy
Satisfied Customers: 29457
Experience:  GM Grand Master Technician 2007. 14 years experience.
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04 silverado 2500hd 6.6 turbo diesel. I have these codes.

Customer Question

hi, 04 silverado 2500hd 6.6 turbo diesel. I have these codes. U1003,U1009, P0840, P0842 and P0700. I'M wondering if the pressure switch manifold might be bad and how difficult is it to replace
JA: Thanks. Can you give me any more details about your issue?
Customer: was driving home, engine light came on, went into limp mode and I believe it is just staying in 5th gear but don't quote me on that
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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?
I am not sure if you have used our service before or not. The experts here are third party contractors. Myself, I am a GM technician in a Gm dealership. I will be happy to help you. Please understand that my only compensation for the time spent helping you is by your rating of my service in a positive way. The more information you provide, the better the chances of getting your issue resolved. Also please reply if you have any followup questions.
So about your vehicle,

the U codes which are communication codes many say otherwise. Give me a few moments to review the codes and see what we can find.

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

Ok, so the U1003 and U1009 could be a problem with engine or chassis grounds. I suggest checking those, namely on the frame under the drivers door and the side of the engine.

As for the other codes, yes the pressure switch manifold is a possible suspect. What I suggest prior to simply replacing it is to check your wiring and connections at the transmission module on the fan shroud, check the wiring to the round connector making sure there is not too much sideways tension on it. If those don't show issues and the wiring does not look like its damaged, then the pressure switch manifold may be bad. Its easy to replace, dropping the transmission pan and replacing the assembly is as far as that goes.

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