What mean this code mux 4520-9 man bus with 3axle what mean this code 4520-9

fix it with quick fix.

it is fine. Make sure you start with it hitched at the top of the mountain and are driving down.

Isuzu uses helms which you can order online or at most auto parts stores. Here is the Isuzu link regarding owners' manuals:

Isuzu Vehicle Service and Maintenance Isuzu com

What is a MUX??

zero symptoms stated, just vague, running lamps.(with an 'S')
running, are parks, old name , PARK.
which lamps are dead, the PARK lamp fees are the largest feed on cars. , 2 in trail, 2 in front, and side markers and the cab is full of parking lamps, called illumination lamps with dim feature.
so do all other things work on car, head lamps
engine run, and HVAC and all that?
Ill now answer ,and pretend you said, USA Liberty, on our USA forum.
does your car have DRL feature, like in canada, mandate.
daylight running lights> ill pretend , NO.
Ill pretend you said all exterior park lamps are dead
and the PARK relay is dead.
the relay feeds fuse 9 and 23, so its not likely both those blew.
the relay is controlled by the BCM brain, so if the brain fails to see the switch turned, there will be no parks, nor relay closure.
if engine runs, ok
and head lamps work ok
and all else work then get the car scanned.
to see if the BCM even sees the park commands are sent out.
if engine dont start or stater sound weak , we'd fix that first.
if only parks fail then the BCM is next. (fuses above ok)
all fuses ok. (we check all fuses first. or read the book to see the complex nature of power and fuses on this car.)

the scans must not show, for example MUX to BCM failures.
the MUX is the combo switch outputs to the BCM.
if no errors there, then we diagnose why the park relay is dead.
its not wired like 1970 jeep. not at all
its run by 2 + computers and a network,

You can bypass it by installing an immobilizer bypass for aftermarket alarms like: DEI CHTHX2 CHRYSLER MUX Type Plug Play Harness XK09 Bypass Module Xpresskit

Start with fuses, does the RKE work, possble BCM is locked up, this is a mux wire system, is there a remote stater in this van, they cause mux wire problems, wires in the door jamb can be broken, I need more info to help you out. GOOD LUCK RDJRP

I just brought my car in because the AC was working, but not blowing cold. The emergency brake light won't go off. And the automatic door locks won't work (the doors lock manually but not auto). We just got the call that the entire fuse box under the steering wheel needs to be replaced. 270 for the part, 300 for the labor. !?!?!?!? It all just happened over the last weekend! They said not to drive it anywhere because you never know and all the electric could go!!! Not sure what caused it, but it sounds like I'm not the only one...