Cat 226 Phantom Electrical Issues (Including Flashing Arm Rest & Park Lights)

[Jointery]

With some helpful guidance from Nige, I'll lay this one out for you. It's unique, so stay tuned as I update you on my phantom electrical/Interlock problem.

CAT 226 Model Year 2000 SN# 5FZ03535

Troubleshooting Interlock issue with a twist (flashing arm rest & park brake lights) similar to other threads for this machine.

History-
Bought this machine about 4 months ago (April 2025), that makes it about 25 years old- brand new to us. At the time of purchase, the machine started and operated generally well for its age. Like my dad always said- "bought experience is the best experience..."

Known Issues at The Time of Purchase-
1. Nonfunctional work lights
2. Fuel gauge nonfunctional
3. Hour meter nonfunctional
4. Float/detent switch nonfunctional
5. Dim console ignition lights when you turn the key to the on position
6. Leaking fuel filter/separator

New Issues Appear After Heavy Rains (the machine was drenched...)-
1. No ignition lights in the on position
2. No start
3. No Arm Rest light or Park Brake light

Initial Troubleshooting & Repair (After Dry Out)-
1. Identified and cleaned rusty lower chassis to frame ground strap connections
2. After the ground repair, ignition lights would come on but no start
3. Changed all fuses and relays for good measure
4. Using SIS2GO test instructions and an aftermarket scan tool, identified and replaced a bad Park Brake switch
5. Machine started and moved a few times and then returned to no ignition lights condition
6. While tinkering, I discovered a loose wire (w/a brass spade of sorts) located behind the fuel gauge). When I touched this spade to a post on the fuel gauge, the ignition lights came on. And you guessed it- the machine started and moved
7. After a few starts, it returned to its no lights condition
8. After tinkering around more behind the upper right operator console, I turned on a light switch. Mysteriously the ignition lights came on again and, you guessed it, the machine started and moved a few times
9. This time the Arm Rest/Park Brake relay was chattering..., so that was replaced a second time. The machine started and flashing Arm Rest and Park Brake starts when pressing Park Brake Switch. No propel...

Current Status-
1. The machine will start if I turn on the light switch but will not move because the Arm Rest & Park Brake lights flash when the PB switch is pressed
2. With the help of a lift, raised the cab a couple days ago. In the process, identified a severed upper chassis to cab ground strap. Later today this strap will be replaced and connections cleaned and dialectric grease applied.
3. While the primary ECM is located behind the seat back. With initial visual inspection, I do not see external corrosion. On this model however, I think the auxiliary ECM is located below the plate in the floorboard area. I'll inspect this space in the coming days

Questions for the forum-
Thank you, Nige, for helping me confirm that I am using the correct wiring diagram for this vintage machine. The diagram shows four ground points/lugs (2 upper and two lower) and I have found only three of them.
1. Where is the second upper chassis to cab ground located?
2. On this year model, could the Aux ECM be impacting Interlock signaling/power and ground?
3. Has anyone had fuse panel connector issues with the 226 machine?

A few photos attached for information's sake.

And BTW, like my failed marriages; after we solve these phantom problems..., we can 'confidently and lovingly' hand this darling off to someone who will love and cherish her...

 

[Nige]

Where is the second upper chassis to cab ground located?

Are you using schematic RENR2863-04.? If so it is hyperlinked. Click on any BLUE component title and it will take you direct to an illustration showing that component's location on the machine.

One of the ground straps is actually a strap as opposed to a cable.

On this year model, could the Aux ECM be impacting Interlock signaling/power and ground?

Potentially yes. You're going to have to go right through the machine from one end to the other checking/cleaning all main harness and ECM connections as well as the grounds.

Has anyone had fuse panel connector issues with the 226 machine?

Same answer as the comment above. Pull the fuse panel apart and clean/repair as necessary. You have to bear in mind that your particular machine is now 25 years old. It would not be surprising to find a few green crusties there and there.

 

[Mobiltech]

Definitely sounds like bad ground has been part of your problem. Turning the lights on creates a path to ground through the lights. Hooking up the fuel gauge probably grounded through fuel level sensor.
Both of these scenarios probably fried what it was grounding through as in the sensor or a light relay or bulb.
Get that strap back on. The other ground should be lower down on the frame behind the cab . It will be a group of black wires on a stud.
The strap is for grounding the cab.

 

[HarleyHappy]

I have often just added ground wires from the cab to the frame and from the engine to the cab and frame.
Extra grounds never hurt.

 

[Jointery]

Thank you Nige, Mobiltech and Happyharley. The documents and advice are much appreciiated.

Quick update-
Focused yesterday on the severed ground captured in my initial pics.
1. As suspected, one of the ground studs (on the frame); twisted off when I attempted to break the nut free.
2. Repaired the chassis/frame stud by drilling and tapping a new attachment hole. Up high I could run a stainless bolt through and use as a stud. I’ll upload some pics later today.
3. When I removed the other end of the strap (lower right facing the cab); I discovered that somewhere in this machines history; someone had welded a new 3/8” ground stud into the corner. The old one had apparently broken off. And die to bubble weld, the ground and individual lugs did not have a clean flat surface to sinch against.
4. Ran a die down on that very rusty stud and will install a stainless backer nut, thick SS washers and outside sinch nut as well. These and all of ground connections will be coated with no-ox/dialectric.
5. Picked up the new ground strap at the local CAT dealer. Some $72 bucks later
I’m in the hunt at my local big box stores for stainless 3/8 nuts and washers.
6. Once the new strap is secured, I’ll focus my efforts back to my original lower ground (inside lower left in engine bay) cleanup. Its the strap between chassis and cab. And like the top ground, it has 10 or more spade grounds laid down on one end of the braided strap. I’ll cleanup the threads with a tap & die and use no-ox instead of white grease…
7. If you are like me, the thought of someone welding on the machine really has my wheels turning… It can be an absolute disaster for the electronics. Especially if the proper percautions were not taken and grounding is already faulty…

I’ll update later again today. Once the grounds are clean and secure, I plan to lower the cab and test fire the machine.

 

[Jointery]

Update #1
1. Upper cab to chassis/frame ground strap.
2. Replaced with new strap.

 

[Jointery]

Update #2
1. Removed lower chassis to frane ground straps and ring lugs.
2. Cleaned and installed existing strap and individual ring lugs.

 

[Jointery]

Update #3
1. All grounds cleaned and attached.
2.Lowered the cab and test fired the machine.
3. Arm rest and park brake lights function.
4. Forward work light (left) functions.
5. Fuel gauge functions.

 

[Jointery]

Update #4
1. Lowered the cab then started the machine.
2. Pressed the park brake switch and Interlock functioned correctly.
3. The machine hydraulics and propel function as designed.

Tomorrow I will reassemble left top control panel and test drive…

 

[Jointery]

Not sure how my smoker made it in this thread but—

This is my backyard. Heaven on earth!

 

[ThreeCW]

Nicely documented ground fix !! Thank you.
This was a good reminder to check my ground points too as my 242B is working well but getting close to 20 years old.

 

[HarleyHappy]

Ohhhhh, I think I could live there in your backyard. You would hardly know I was there. I could pitch a tent. You got any wild pigs around?
Would love to go to Texas, hunting.

 

[Jointery]

Closing this troubleshooting effort on this machine. It appears that we have resolved our primary (start & propel) issues. The machine starts and operates as designed.

We do have a bad fuel sending unit, blown bulb and a fried right console logic board. But the ground had to come from somewhere…

A big thanks to each of you for your assistance on this. This has been going on now for three months. And you helped resolve the problem with a few hours.

 

[Jointery]

Ohhhhh, I think I could live there in your backyard. You would hardly know I was there. I could pitch a tent. You got any wild pigs around?
Would love to go to Texas, hunting.

We do have wild pigs on our farm!!! Thank you HappyHarley!!!

 

[Jointery]

Nicely documented ground fix !! Thank you.
This was a good reminder to check my ground points too as my 242B is working well but getting close to 20 years old.

Be prepared for the ground studs to break off. Most of us are handy, so weld or drill and tap a new bolt stud.

But you MUST check and thoroughly clean the stud base and threads of each attachment. That includes running a tap through the nuts. In my case I replaced all but one of the sinch nuts. Also use a backer nut and very clean washers. You want a large very flat surface for the grounds to land on. Clean the straps and the ring lugs thoroughly as well. If the strap is questionable, replace it.

Lastly, use a good quality no-ox protective grease on every surface and every thread. Use lot’s of it and be sure if you grind a new stud land point area coat it thoroughly on both sides and the threads. This is what i used. Not compensated for this in any way. Its what i found at the big box store

 

[Jointery]

We do have wild pigs on our farm!!! Thank you HappyHarley!!!

Correction- HarleyHappy!

 

[Jointery]

A shot of the cab ground landing. I think my thumb saw the smoker and missed this important shot!!!

 

[HarleyHappy]

In my magical drawer in my tool box, I keep a very important bag of necessities. They are called star washers and are very important in keeping contact in ground and power applications. Every once in a while, I buy a bunch of different sizes for my magical bag because they tend to get used.