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CAT 420F HAND THROTTLE SWITCH NOT WORKING - Need Wiring Schematic

J

Jason Wedel

Member
Joined
Dec 18, 2019
Messages
7
Location
Colorado
I recently bought a used '13 420F and among other issues I've found, the hand throttle dial doesn't work. I tested a few 420's at ritchie bros the month before I drove it and those didn't work either - is there some kind of safety switch or procedure to allow it to engage? It looks like the previous owner threw in a new Chinese switch off ebay but it didn't solve the problem. Also, the tach needle winds up when you first turn the key, but it doesn't register engine speed when the hoe is on - not sure if it is tied to the tach? The floor throttle pedal works fine. A wiring diagram/schematic would be very helpful if anyone has one on hand they could email me.

Any insight or possible areas to check into first to narrow down the issue would be appreciated. I can get a new cat switch on ebay for $120 but I have a feeling it isn't that.
 
Nige

Nige

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G..G..G..Granville.........!! Fetch your cloth.
Multiple (10 actually) model numbers of 420F, model year means nothing unfortunately. Everything is based on Serial Number.
Send me a PM with your S/N and an email address - I'll send you a schematic.

Also I strongly advise that you get an Operation & Maintenance Manual (O&MM). You can download one from Cat for less than $50. That will give you plenty of information about how the all controls are SUPPOSED to work, not how you might be assuming they work. Again with a S/N I can walk you through the procedure.
 
Last edited:
J

Jason Wedel

Member
Joined
Dec 18, 2019
Messages
7
Location
Colorado
laycobeau said:
Cat says anytime you hit the brake you have to turn the dial back to 0 then back up to work ????
Click to expand...

I wish that worked - it won't throttle up at all, brakes or not. I'm wondering if it has something to do with the auto throttle feature but this is the first machine i've had that isn't all mechanical. Not sure "upgrading" was the right thing to do.
 
J

Jason Wedel

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Dec 18, 2019
Messages
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Location
Colorado
I plugged the computer in to the hoe and the switch is working perfectly, and everything else seems to be in order aside from the fact that the reading on the engine speed is "-1".. I'm guessing this is my problem. Has anyone else seen this? Is it as simple as replacing a engine speed sensor?
 
Nige

Nige

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G..G..G..Granville.........!! Fetch your cloth.
Did you find any electronic fault codes regarding the engine speed sensor..?
It might pay you to have a close look at the engine speed sensor wiring. Who knows, you may find something obvious.?
Also the nose end of the sensor could be contaminated with metal particles, it won't be the first time.
 
J

Jason Wedel

Member
Joined
Dec 18, 2019
Messages
7
Location
Colorado
No fault codes on the sensors. Wiring looked good, i put new sensors in and fixed a can resistor that was unhooked and now when it starts up and i move the hand throttle the green throttle light goes on for 20 seconds or so and then goes off. Still no tach or change in engine speed when using the hand throttle. The computer recognized the hand throttle movement (each click) but it still shows "-1" value for engine speed.

I am getting a code 3084-3 AESC Enable Switch: Voltage above normal when auto throttle is turned on. Any ideas for shots in the dark on the next move?
 
J

Jason Wedel

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Joined
Dec 18, 2019
Messages
7
Location
Colorado
I installed two brand new speed sensors - figured while i was in there I might as well put new ones in so I don't have to get back in there again or second guess it.
 
J

Jason Wedel

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Joined
Dec 18, 2019
Messages
7
Location
Colorado
Thanks for that - i have that resolved now but it wasn't what was causing the hand throttle not to work.. A little more digging and i realized there has been a code that i've been ignoring but I think it may be the cause. If you have diagnostic procedure for this one, from what i've read it may be the culprit. 247-9 SAE J1939 DATA LINK: ABNORMAL UPDATE RATE.
 
D

dukes0520

New Member
Joined
Apr 24, 2023
Messages
3
Location
58601
I have a 420 f IT back hoe serial #0420fkjwj02255 I'm looking for a wireing schematic for the tps sensor.or a diagnostic table for code 92-4 can anyone help?
 
Nige

Nige

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The 92-4 has me confused. The Code for the TPS is 0091. How are you reading Codes.?
FMI04 is "voltage below normal" which usually indicates an open circuit somewhere, often in the signal line. See attached.

Check your messages for the schematic.
 

Attachments

  • Analog TPS Test.pdf
    1.1 MB · Views: 8
D

dukes0520

New Member
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Apr 24, 2023
Messages
3
Location
58601
I was reading fault codes from the dash.i don't have a access to software and this point in time .back how came in idling at 1500 rpm with no throttle response from pedal.installed new tps sensor still have active code on dash I've checked voltage at tps and the best that I can tell is the 5 volt reference is only at 1.4 volts.
 
G

Grant Roark

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Apr 15, 2024
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1
Location
Monett
Do you happen to have a wiring schematic for the foot throttle for this 420F2 SN: HWC03999? We have code 91-4
 
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