I have a 420F that has no foot throttle response, the rear throttle dial idles up the engine fine. I installed a new foot pedal and it made no change. All the fuses are good except a fuel fuse that keeps blowing. Anyone have any suggestions?
I would think find out what's causing the fuse to blow and fix it as a first step. If you want an electrical schematic then please post a machine Serial Number.
Thanks for the quick response. The serial number is CAT0420FEJWJ00225 Stupid question, but is that fuse symbol for the fuel pump
Do you have cat et? And are there any codes on the display? The older models would have the connecter at the pedal, sometimes the individual terminals would spread open or back out.
No I don’t have it, but we’re looking into getting something for diagnostics. I have 2 lights on the dash but I don’t think I can pull codes from this panel. A new foot pedal was installed a couple of days ago. I added a photo of the dash
If you had cat ET it would be simple as looking at the code and pedal position. You can try to unplug the electric fuel pump and put another fuse in. See if it’s the pump or the wiring.
Actually you can pull Diagnostic Codes and Events from that panel. See the attached. Come back with whatever you find. Fuse F2 is for the Fuel Pump and Secondary Engine Stop. Also check your message inbox for an electrical schematic.
I unplugged the fuel pump, put a new fuse in and turned the key without plugging the connectors back in and it blew the fuse again, looks like it might be a wiring issue I’m gonna guess.
Well Nige got you the wiring diagram and said that fuse also powers the secondary engine stop. If you share the diagram I can take a look. I’m on vacation and don’t have access to sis right now. Were you able to get the codes as well?
Awesome, that’s a big help, but I can’t see how I can pull the codes from that panel, this is a used machine we got recently and unfortunately there was no manual included
I didn’t see how to pull the codes from that panel, can’t see if there is a sequence of buttons or pedals to push to retrieve them
Read the farkin attachment in Post #7...........!!
Thanks, I’ll see what I can get from this and check back tomorrow, much appreciated!
I read the schematics several times and never seen the button sequence in there, i got it now though thanks
And can you take a pic of the fuse box and the fuse that is popping. Just to confirm it’s the fuel pump. Because I followed that fuse only to the fuel pump relay. I couldn’t see on my phone if it went to a secondary engine stop, but haven’t heard of one before. And it looks like it only goes to the fuel pump relay. You can pull the fuel pump relay and try a new fuse tmr. Every backhoe I’ve worked on though even with the fuel pump not working or fuse missing, it will still respond with the accelerator pedal. That’s why it’s important to check the codes.
Soooooo any update?
I was out of town for a couple of days. I got into the panel and took pics of what was in there. And F2 is the fuse that keeps popping
So you have three Active Diagnostic Codes, as indicated by the "X" shown on the RH side of the display. 91-4 - Accelerator pedal position sensor - voltage below normal. 3510-4 - 5v DC sensor power supply - voltage below normal. 1076-5 - Engine cooling fan bypass solenoid - current below normal. I can't see any of those three Codes causing F2 to blow, so i think your best bet is to use the electrical schematic and trace/test the wiring downstream of F2 for a short circuit somewhere. First place I suggest to look is the fuel pump relay. F2 supplies key switch power to Pin 30 of the relay. try pulling the relay out and turn the key on. Does F2 still pop.?
Moving on to the issue of the throttle. The troubleshooting procedure for 91-4 specifically states that it only applies if there are NO 3510-X Codes present . So that leads me to believe that your next step after finding the wiring issues causing F2 to blow would be to troubleshoot the 3510-4 Code. Conditions required to create a 91-4 Code The ECM has been powered for 3 seconds. Diagnostic code 168-4 is not active. 3510-X codes are not active. Attached is the troubleshooting procedure for the 3510-4.
Looks like the harness is chaffing on the body somewhere. I’ve done a few. Gonna take off the floor board under the rubber carpet thingy and pull that harness. I usually pull the starter so there is enough room to get the harness out. You’ll be going for the connecter on the ecm that is closer to the rear. The plug is too big to fish thru that’s why the starter needs to come out. Also the 2 ground wires have an Allen key that gets rounded so a tiny pipe wrench works better than vise grips in that space. This job sucks, so if you can find the area and repair on the machine, go for it.
My apologies for the late response. I pulled the relay for the fuel pump and the fuse still blows. I will start pulling panels and the starter either later today or tomorrow morning.
Hey so I disconnected the fuel priming pump again, put a new fuse in and it didn’t pop.
I disconnected the fuel priming pump, put in an new fuse and it didn’t blow, then I put a test light on the yellow wire and got power, but nothing on the black wire
You have the electrical schematic. From that it's clear that X977-EN39 YL is the power wire, and 200-EN67 BK is ground. You're not likely to find power on that one. Do you have a good connection to ground on the black wire.?
Did you plug the pump back In and check if it pops again? You can always make a plug and put 12v to the yellow and ground to the black side on the pump and test if your throttle problem is solved from The fuse being popped.
Wiring isn’t my strong point but I’m working on it. I’ll trace that black wire in the morning to see if I can find any grounding issues. The machine starts up fine and idles just fine, and it will rev up all day with the dial in the rear but just no foot throttle, I’m assuming there’s another wiring issue there for the pedal?
Try the last thing I posted. If the fuse doesn’t pop, and it runs off the 12v jumper wire to the pump and still does not respond from the acc pedal, then we will check the connected for the acc pedal. The connecter doesn’t come separate from the harness. It usually has one of the terminals walk backwards or gets spread open. Take a clear pic of the acc pedal connector so I can see.
Thanks guys, be checking back in the AM with what I can find
Not sure if I’m doing it right but I disconnected the fuel pump connector and made a plug for the 12v power supply, I gave the fuel pump direct power from a 12v battery to see if I could hear it but it didn’t do anything
Did you already try to plug the pump with its original machine harness and see if it blew the fuse? If you put 12v on the yellow and ground on the black you would hear a pretty loud humming. Even if you got the wires reversed it would hum and flow backwards. And can you test the pedal connecter for 12v on all the pins with the key on engine off.
Check the orange wire for 5v, not 12v.
I’m getting 7.8v on the orange. As for the pump I’m thinking it’s gone bad, I rigged up a couple wires and ran another pump off the harness and the test pump ran fine when I turned the key. When I plug the old pump back in it makes no noise at all
There is an improved pump available which suggest there was a problem with earlier versions. The improved pump was fitted ex-factory from S/N JWJ02104, so after your machine was built. Search for 446-5393 or an aftermarket equivalent.
I managed to find a pump online. I went into the fuse panel again and noticed that both fuses on #47 PRM module ENG have power but the wire post for the 50amp fuse doesn’t have power. I can see in the diagram that it switches from PL640 to PL642
The colour a wire is drawn on the schematic identifies the function of that wire. All wires drawn in RED carry permanent Batt+ voltage. That being the case, at the outgoing side of the #47 PRM Eng Module Relay the wires 150-PL640 & 150-PL140 connected to the terminal marked "USB" (unswitched battery) will always have power. The outgoing wires 384-PL642 & 384-PL128 connected to the terminal marked "SB" (switched battery) will only have power when voltage is supplied on wire 310-PL147 which pulls in the coil of the #47 relay. Wire 310-PL147 comes from the Engine ECM.
Ok thanks, I was pulling at strings for the fuel pedal issue.
I went over those pins again at the pedal connector and I’m not getting any voltage to the orange wire
Yeah if the wire is shorted intermittently, the ecm will see that and shut it down. Can you check for ground at the orange wire now when voltage isn’t there
Key on or off now I’m getting nothing to the orange.
You can always unplug them one by one and see if the 5v comes back on with key on. Sorry I’m traveling for the next 2 days but will be back to work and able to get some known good readings for you.
I went through the machine and found the grounding strap for the ECM under the cab floor was corroded off, that’s been fixed. I’m looking at pulling the muffler box off, if there’s any issues with wiring in there would I still be able to idle up the engine with the analog dial?
Yes the idle switch on the back is separate.
Did you check for ground at the orange wire?
It looks like I found a bit of a problem here. Took off the muffler box and the wires for the DPF system are burnt, and all 6 wires from that harness are black. I’m trying to get the casing off the wire but it looks to be fused to the wire from heat
Yup there’s the problem. So you can carefully razor off the harness protector, and replace the wires one by one. As long as you can see which wires run all the way down, you should be able to do this without mixing them up. I don’t think cat makes that pigtail, it comes as the entire harness.
Perfect, I managed to strip those wires and run new ones, finally I have full function from the accelerator pedal! I have one new code in the panel 3242-4 which looks to be the DPF outlet temp sensor
Thanks for all the support on this one guys! Greatly appreciated!!
Awesome to hear.