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Poppystate

Member
Joined
Oct 20, 2020
Messages
5
Location
Sacramento
Occupation
Small excavation business
Machine is going into limp mode right at startup with warning alarm. Used to happen every now and then. Would turn off, back on and would clear up for a while. That will let the machine get back to work. Due to the responses on this website on other threads, I think I diagnosed it to the wheel speed sensors. Wire harness is good with good voltage (8v,5v). Just weird that I think both going out at the same time. I do have a couple questions on a few other codes. I will list all of them below

4336456
E875-2
E123
E570-2
E568-2
E569-2
2686-8
2688-8
2687-8
70-3
3700-13
 

Nige

Senior Member
Joined
Jun 22, 2011
Messages
29,445
Location
G..G..G..Granville.........!! Fetch your cloth.
This machine has 4 speed sensors. A pair on the RH side and a pair on the left. The sensors supply a PWM signal to the machine ECM.
Each pair of sensors is mounted in a common body with a common power supply & ground. Each sensor has its own signal wire in the harness, so four wires total in each narness.

2687 & 2688 are the RH #1 & #2 speed sensors. The first suspect would be a fault in the common ground or power supply.
2686 is the LH #2 speed sensor. As there is no code for 2685 (LH #1 sensor) the first suspect would either be in the signal wire or a defective sensor.
-8 indicates an abnormal signal from the sensor i- frequency, pulse width, or period.

Post a S/N. with that detailed diagnostics and an electrical schematic can be lkocated.

BTW E568, 569, & 570 all relate to issues with drive motor speed, so they will also be related to the sensor faults.
 

Poppystate

Member
Joined
Oct 20, 2020
Messages
5
Location
Sacramento
Occupation
Small excavation business
CAT0299DKNLC00311

So there is sensors on the drive motors themselves. I’ve checked those yellow wire voltages one at 8 and one at 5.

So you’re saying there is other sensor under the cab somewhere
 

Nige

Senior Member
Joined
Jun 22, 2011
Messages
29,445
Location
G..G..G..Granville.........!! Fetch your cloth.
No. the speed sensors are mounted directly to the drive motors. The sensor is #1 in the illustration below.
If you were measuring voltages with the sensor disconnected that's not the correct way to do it. You need spoons for your DMM and measure voltage into the back side of the connector with it still plugged to the sensor.
The sensors are fed with stabilized 8v from the ECM. There is no 5v at that point.

upload_2020-10-24_19-24-57.png
 

Attachments

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Poppystate

Member
Joined
Oct 20, 2020
Messages
5
Location
Sacramento
Occupation
Small excavation business
So just want to double check this cause I’m kinda a dummy sometimes.. the white and yellow wire according to the manual should both produce 8 volts
 

Nige

Senior Member
Joined
Jun 22, 2011
Messages
29,445
Location
G..G..G..Granville.........!! Fetch your cloth.
So just want to double check this cause I’m kinda a dummy sometimes.. the white and yellow wire according to the manual should both produce 8 volts
Not exactly. Yellow wire is 8v sensor Supply, White is sensor Return. Temporarily disconnect the speed sensor from the machine harness at either of the connectors shown below. These are the connectors right by the motors.
Connect your meter between the terminals of the yellow and the white wire at the machine side then power on. You should see 8v.
Repeat the process for the sensor on the other side of the machine.

upload_2020-10-27_18-15-37.png
 

ColdBlackWind

Well-Known Member
Joined
May 26, 2023
Messages
135
Location
Trigonia, Tn.
Working on the same issue. Is anybody still out there? What do the sensors cost and what is the p/n#? I am having a devil of a time using the Cat online parts look up. Probably me but I can’t get it to recognize serial number or description of part.
 

Nige

Senior Member
Joined
Jun 22, 2011
Messages
29,445
Location
G..G..G..Granville.........!! Fetch your cloth.
I can find the Part Number and the last time I saw a price it was North of $300 per sensor. The thing is you may not have a defective sensor, it could just as easily be a wiring harness fault.

Start with a Serial Number please.
What S/N are you putting into the Parts system (parts.cat.com I assume?) that it won’t recognize.?

Then give some details of the problem symptoms. Have you have accessed Diagnostic Codes yet.?
 

ColdBlackWind

Well-Known Member
Joined
May 26, 2023
Messages
135
Location
Trigonia, Tn.
I downloaded your troubleshooting files from previous post. Just got in. I will dig around on the wiring later in the weekend. Just got the machine 10 hours on it so far.
 

Nige

Senior Member
Joined
Jun 22, 2011
Messages
29,445
Location
G..G..G..Granville.........!! Fetch your cloth.
It has the lcd screen display. 2018 model.
In that case..........

Press the soft key located directly under the "settings icon" (#40) on the screen. That should get you into the Main Menu. Scroll and find the "Service" section and then to the "Diagnostics" sub-menu. AFAIK it should have 4 sub-sections - Active Diagnostic Codes, Logged Diagnostic Codes. Active Events, & Logged Events.

First check for any Active Diagnostic Codes or Events.
Then go to the sub-menu for the Logged Codes/Events. Take a note of everything that is listed there and post back with your findings. Logged (non-Active) Codes/Events can be just as informative as Active ones.
 
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