2017 Express 4500 cutaway
 

Howdy!!! Hoping I can maybe get some direction here. Frustrated doesn't begin to describe my attitude with the RV right now. Specifics....2017 Chevy Express Cutaway RV (Coachmen), 6.0 , automatic....10,000 miles...Crank/no start...Checked error codes...P1682......Checked grounds, changed the ignition switch, swapped a couple of relays with each other (it appears several are the same in the fuse block under the hood), tried finding a wiring diagram to try to troubleshoot but could not find a match for this year/type/model (I know that many models are similar but no luck so far).
Background: RV is driven infrequently but started at least twice monthly during the offseason. Started everytime until I went to use it!!!! Crank but no start. Plenty of gas. The only thing I have been able to sleuth is on the fuse block under the hood there appears to be one "bank" of fuses (#'s 61-65 and #'s 75-79) that have a low voltage when key is in start position (1.56 V)...I am assuming there is a relay that feeds these because they are 10-20 amp fuses. Guessing it is not directly from the ECM. Any help would be appreciated.....:confused:

I'm not a real van guy, but here is what I found about the GM code P1682:

P1682 CHEVROLET Possible Causes:

Faulty:Ignition Switch harness is open or shorted Ignition

Switch circuit poor electrical connection

Faulty Engine Control Module (ECM)

I hope it's not the ECM, Those are not cheap, but like anything, they can go bad.

Thank you....found those as well....still trying to determine where there may be a "faulty electrical connection" but cannot find a wiring diagram. Thinking I may pull the fuse block and check connections on rear of that. Thanks for the response!!!!

wiring diagrams on gmupfitter.com

2017 Chevrolet no start problems
 

check your grounds there is one particular ground on the left rear chassis that controls the fuel pump I've had found this to be a problem with several vans.

Found it....hope it helps someone else
 

After numerous troubleshooting sessions everything kept pointing to a loose connection on the back of the fuse block. The problem was showing itself as low voltage on a certain section of the fuse block, and of course the no start problem. Turns out the fuse block is not just a simple connection block but contains some micro circuitry on the rear of it with numerous small components that can go bad. Only discovered this through a frustrated Sunday night session where I determined I was going to pull the whole vehicle part if I had to... Pulled the fuse block and saw that it was more than a simple connection. Ordered a new one the next morning for $196 from the Chevrolet dealership. Had it within 2 days. 30 minutes later the truck started 🤪... Hopefully this will help someone else...

We have a ‘15 4500 chassis under our class C and it’s had intermittent electrical issues for several years. The latest being the climate control.
How much of a struggle was it to change that fuse panel?

30 min out and back in....couple power connections and three bolts...you will have to separate the"holder" (plastic carrier under the fuse block) once you have it out. Took me a little while to figure out they came apart, and that the part the dealership sent me was the correct part. Looked different until I determined what I removed is actually two pieces that look like one. Once I saw the panel could be removed is when the light bulb came on 💡

Great, thanks. Can’t find the PN on any of the usual sits so, headed to the dealer tomorrow to order it and the one under the seat.

Have had this issue
 

I have had to replace the crank relay every time i let my camper sit until I started using a battery tender. Why this has helped I dont know but I havent had to replace the relay in a long time and I have replaced a bunch of them and still keep good ones in my camper.