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Jeremy, Certified Truck/Bus Technician
Category: Medium and Heavy Trucks
Satisfied Customers: 3382
Experience:  ASE Med/HD Truck Technician, NATEF Diesel Engines and Electrical/Electronics Technician, EPA 608/609 HVAC Certified, Steering/Suspension and ABS/Brakes Technician
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Have a cascadia 14.0L Detriot engine 13spd the truck does

Customer Question

Have a cascadia 14.0L Detriot engine 13spd the truck does not accelerate so I decided to disconnect the clutch pedal sensor and it now Accelerates so I thought it would be a bad sensor replaced it eight the new one and still the same problem my speedometer doesn't work either so I replaced it with a new one and still the same problem
Submitted: 10 months ago.
Category: Medium and Heavy Trucks
Customer: replied 10 months ago.
Fault code subbus switch missing 523530 FMI 31
Customer: replied 10 months ago.
Hello anyone ??
Expert:  Jeremy replied 10 months ago.

My name is ***** ***** I will assist you with your question today.

I'm an independent contractor and I don't get paid until a rating has been made.

We can go back and forth as needed to help resolve the issue you are having. Follow ups are free after ratings, so rate in confidence!

I apologize on the delay. I was told this was in the wrong category and just got moved to the right one.

Here is the information for the fault. I will say that you will want to take this to the dealer or to a shop that has the Detroit software to diagnose this further because if one of the regen switches are acting up (which is most likely the case here) ther truck will go into a limp mode and cause the accelerator pedal to not allow the truck to rev up properly. Removing the clutch sensor will bypass it until the truck sets the code for it and then you are back to square one.

In regards ***** ***** speedometer not working, that could be a separate issue. The concern is if the signal is making it to the SAM and then not going to the ICU or if the SAM isn't even getting the signal. This truck is highly computerized and needs a diagnostic computer to diagnose it properly.

I'm posting the fault code info below from the service manual.

Fault Code 523530/31

This fault becomes active when the

MSF Master does not sense one or

more switches on the sub bus that it

expects due to MSF parameter


Action: With the key ON, connect to the vehicle with ServiceLink. Go to the MSF "Switches" screen, and note which switches

are marked as missing. For each missing switch, determine whether or not the vehicle should have that switch installed. If it

should be installed, install the switch. If it should not be installed, set the appropriate MSF parameter (based on switch ID)

to make that switch "not available". If the switch is already installed, the fault indicates the MSF Master is not sensing the

switch on the sub bus. Check the connections between the switch, MSF slave and sub bus connections to the MSF master

The other one is an INFORMATION ONLY fault.

Remove the MSF master(Hazard Light, Red Triangle on the Dash), make sure there are not any connectors that have fallen out of the back.

The Sub bus switches are your Engine Brake, Fan manual, Regen Switches, these are the switches that are connected to the Sub Bus.


You want a 5 star service and I want to provide a 5 star service. Please consider that I don't know your skill level as well as I can't see, touch, smell, hear the vehicle/machine in question. Please provide as much detail as possible and I will provide as much back.

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Customer: replied 10 months ago.
Ok I will take apart the MSF MASTER and I do have the Detriot software how do I see what switch is messing up when i connect software ?
Expert:  Jeremy replied 10 months ago.

You have the new software? Is it the Standard or the Pro version?

I use the pro version. After all the modules load, there is a section for instrumentation. You click on it and you see smart switches. You click on that and it will highlight all the switches you have. They will have a diagram that shows them on or off or fault if there is a fault with them.

Customer: replied 10 months ago.
Ok I have the standards version. And let me hook it up worked really late last night
Customer: replied 10 months ago.
It seems like the idle validation switch 2 is red off ground
Customer: replied 10 months ago.
Hello sir
Customer: replied 10 months ago.
Customer: replied 10 months ago.
Ok I will
Customer: replied 10 months ago.
Looks like nothing is loose here
Customer: replied 10 months ago.
These are the codes I have my truck doesn't not accelerate
Customer: replied 10 months ago.
Hello sir I found the missing subbus it's the footwell that says it's missing how does that affect my acceleration??
Customer: replied 10 months ago.
Hello I need help
Expert:  Jeremy replied 10 months ago.

The idle validation switch is showing a "ope" circuit meaning the switch is bad. It is inside the accelerator pedal sensor. It is part of that switch. Either the switch in it is bad (which is resolved by replacing the sensor) or the wire has a rub through to where it lost connection. MOst times it is the sensor. It will affect the idle for sure. Swap it and see if the issue resolves.

Customer: replied 10 months ago.
Ok it seems like it comes with the whole pedal complete
Customer: replied 10 months ago.
It doesn't let me
Accelerate when I drive either this should be a problems?
Expert:  Jeremy replied 10 months ago.

It won;t let you accelerate because there i an issue with the sensor. The truck can't see if you are idling or if you are throttling so it shuts the circuit down. That is to keep the truck engine from "running away."

Customer: replied 10 months ago.
Ok let me replace it and I'll
Let you know
Expert:  Jeremy replied 10 months ago.

Sounds good.

Customer: replied 10 months ago.
Just replaced the pedal and the same thing I also replaced the clutch pedal with new sensor and still the same issue
Customer: replied 10 months ago.
I followed the wires and they don't seem to be damaged