I am having some trouble with fault codes on a Cat 272D2 track loader. After it runs half an hour code 3233-12 ACU will come on the screen and it will derate. If you shut it off for five min. it will start up and run fine for a little until it does it again. The code will not show active in the menu and my Diesel Laptop will not pick it up. It also has code 350-3 on all the time. It is not getting power to one wire at the boom sensor. Yellow wire 117 E2 if I remember right. I ran a 12V jumper wire to that wire and the code goes away.
Got a Serial Number.? You're going to need an electrical schematic either way. 3233-12 is for the NOx sensor heater control. 350-3 is the lift position sensor - voltage above normal.
Sure, the serial number is: CATO272DHBL200275
For the 3233-12 you will need to run the NOx Sensor Test. Procedure for 350-3 also attached. You will also need an electrical schematic. Check your message inbox.
Thank you for the two diagnostic procedures. I will follow them and see if I can find the problems. Where would be the best place to get the electrical schematic? I have been thinking about getting SIS 2.0 from my local dealer. What all does it have on it? I would be glad to hear any thoughts.
If you look in your message inbox (click the red envelope icon in the top RH corner of the screen) you will find one there waiting for you.
I have not been able to get the wiring diagram yet. I see a envelope icon beside my user name/login but it is not red and if I click on it, it says conversations and there are none. What am I doing wrong?
It turns out you are not doing anything wrong. I could have sworn I sent the schematic to you, but it turns out that I hadn't so for that my apologies. Check your message inbox now.
Update on the CAT 272D2. I found a broken wire in the wire harness to the lift angle sensor. Fixed the wire and that code goes away. I'm still having trouble with the code 3233-12. I followed the diagnostic test on pre. NOx sensor. It has 5 wires going to it. Power, ground, CAN high, Can low and ground. The power and grounds checked ok so I replaced the pre NOx sensor. It still runs for about 5 min. and then it throws the code and derates. You shut it off for a few mins. and it will start back up and run fine until it does it again. I'm not sure where to go from here.
You need someone more familiar than me regarding aftertreament systems and their diagnostics. Hopefully someone will chime in with suggestions.
This is another code it has now 2204-3 Auxillary Lever 1 Position Sensor Voltage above normal. I don't think it is a big deal but it would be nice to fix it.
So the reason you can cycle the key and get away with full power for a few mins is because this is still in the beginning stage of operator inducement. Eventually you will only be able to idle, and it will be way harder to clear those codes. If you followed the troubleshooting chart already, you probably have a faulty sensor. The sensors on the muffler system usually have a set temperature and time limit before they start reading. This is to prevent them getting damaged by moisture (they have a heating element). That’s why it isn’t active and causing derate until the 5mins mark.
Thank you for responding, maybe you will be able to help me more. I have replaced the sensor. It comes as one unit, the sensor, harness and control module. It has 5 wires going to it, power, ground, CAN high, CAN low, and ground. The power and grounds seemed to check ok unless I missed something. From what I understand about the code, it means that the CAN message is indicating NOx sensor error (Open circut or shorted circuit of the NOx sensor heater. I highly doubt that the new senor is bad, the old one was probable good. What could be happening that the would cause the ECM to trigger that code? Is there some other parameters I should look at to understand what the system is doing? I don't have CAT ET but I do have Diesel Laptops diagnostic tool.
Are you sure you're checking the correct sensor? 3233 is for the post NOx sensor. 3223 is for the intake side sensor.
Thank you for your response. That may be the answer to my problem. I did replace the pre NOx sensor. Here is where my confusion may come in. 3223-12 Aftertreatment #1 Intake Gas Sensor Heater Control Failure. 3233-12 Aftertreatment #1 Outlet Gas Sensor Heater Control Failure. I was looking at Aftertreatment #1 and thinking that it meant Pre NOx sensor and that After treatment #2 would mean Post NOx sensor. I missed the intake and outlet part and that's what determines whither it is Pre or Post? I think I need to check the wiring to the Post NOx sensor and if it is ok replace the sensor. Is there anything else I should check also? These parts are $$$$. What do you think?
If your code is definitely 3233 and not 3223 then you need to be troubleshooting the post NOx sensor. It has 4 wires compared to the 5 you checked on the pre NOx sensor. All you can check for is power and ground. Use a test light capable of drawing some current - not a DMM. Do I think they're expensive? Yes, I do. And they are both different part numbers.
Ok I'll do that and see what happens.
did you have a chance to grab a new sensor? So for future reference, if you aren’t sure what sensor is which, unplug and see if a new active code comes on. Usually if the harness is good, a new active code comes on within a few seconds.
No, I have not yet. It may be the middle of the week until I get it. I'll let you know what happens. While I'm waiting can you CAT guys explain CAT codes to me to help me understand them better? What is the ECM seeing when it says voltage high, voltage low, currant high, currant low ect. ?
So the majority of cat machines that I work on, circuit high and voltage above normal will mean that the circuit is open. Most likely to a wiring fault or connecter unplugged. Also can be from a component failing but not shorted. Current/voltage below normal can be from the fuse popping, sensor shorted internally. Most everytime you can unplug an easy sensor, like the intake temp/ambient temp sensor. And check if you get a code with the voltage above normal. Then you have an idea of what to expect. Some times you get the opposite. The one I did today. Accelerator pedal #1 voltage above normal. Unplugged the connecter, code remained and no new codes came up. One of the pins was spread open. Replaced the pigtail, all is good. The one I did last week was dosing unit current below normal. Def injector shorted internally. Unplugged it, waiting a few seconds, code changed to dosing unit voltage above normal.
There's a couple of things to know. 1st: There's more than one kind of data link and each gives its own different (but not unrelated) codes. CDL (Cat Data Link). Oldest and slowest. Gives fault codes in the format of MID/CID/FMI. This is what people with the older generation of Cat machines with electronic controls are dealing with today and most of the troubleshooting advice on this site relates to. J1939 . This is a newer and faster data link. Fault codes are delivered as SPN (Suspect Parameter Number). When dealing with the current generation of Cat machines, it's not uncommon to find both CDL and J1939 data links in the same machine. For this reason it's important that you know which type of code you are dealing with before you embark on troubleshooting. Fortunately, most newer machines also tell you the meaning of the code on the display in plain English. Ethernet . Newest and fastest. Used on the latest machines alongside the other data links. Outside the remit of this discussion right now. 2nd thing to know. The ECMs/ECUs on a basic level have three types of connection; Inputs Outputs Data links. Each has its own type of FMI (Failure Mode Indicator) So to finally answer the question Inputs from sensors will (amongst other FMI) commonly show FMI 3 or FMI 4. Voltage above or below normal. Voltage above normal is associated with the signal wire having an open circuit. Voltage below normal is associated with the signal wire having a short to ground. This is all to do with pull-up voltage which is another subject. Outputs to coils, solenoid valves, relays, etc. (They're all fundamentally the same thing) commonly show FMI 5 or FMI 6. Current below or above normal. Current below normal is associated with the signal wire having an open circuit. Current above normal is associated with the signal wire having a short to ground.
I will give an update on the 272D2. All the problems are fixed. No active codes, no stored codes and no warning lights on. A very good feeling to have. Here is what the problems where: 350-3 The power wire to the sensor was broken inside the insulation. I replaced the wire between plugs and put new loom on the harness. 3233-12 The post NOx sensor was bad. I replaced the pre sensor first because I read the diagram wrong. Once I replaced the post sensor the code went away. 2204-3 The roller switch on the right joystick was bad. I could wiggle it and get the code to go away. I replaced the handle and that fixed that code. CAT parts are the best but they are the most $$$$$$ ! Thank you for all the help on this! By the way has anyone found another option for those roller switches? They are very expensive. I saw some talk about them on this forum in the past.
There are certain options available for the Hall Effect thumbwheel roller switch on earlier models although none are a perfect solution. With that type of switch the usual failure mode is that the magnet disintegrates. Your newer D model uses a PWM position sensor under the thumbwheel roller and AFAIK there is no workaround for a failure of that sensor type other than replacing the complete handle. The biggest obstacle for both the above types of thumbwheel roller is that all commercial thumbroller switches on the market seem to be designed to operate on a stabilised 5v DC power supply where Cat uses an 8v supply and has roller switches manufactured exclusively for them.
That is kind of what I found. The magnet was ok on mine and you could wiggle it to make it work, but I could not see anything wrong with it. The roller switch should only cost $80.00 to buy it it's self but instead your paying $1000.00 for it and I'm sure that is way more than it cost to make it. Why does CAT do that?
The simple fact is that Cat electronics have always operated on 8v DC. For the number of switches they buy it's easy enough for them to have a switch specially made by a company such as Otto to work on their voltage rather than trying to adapt the machine to the available over-the-counter 5v switches. Quite why they do not offer the switch as a separate spare part I have no idea.
So any time they use "reference" voltage on sensors it is going to be 8V ?
It depends on the output of the sensor. Analog sensors tend to run on 5v. PWM sensors tend to run on 8v. This isn't a hard rule. Some sensors may work on 10v and even 12v.
I was going back over this post and it is really good information. Some questions I had. How do I know if a machine uses CDL or J1939 or what about a machine that uses both? Is Ethernet only used on the really big machines like mining equipment that is very new? Was the clicker box used before CDL or is it how CDL was when it first came out?
A fault or event will be identified through either ET or the PSR (product Status Report). A quick way to find out which data link a machine uses is to look at the service connector on the wiring diagram. This is your machine. Most machines up to maybe 10 years old will have both CDL and J1939. The newest machines no longer use CDL. Ethernet is usually associated with digital technology, grade controls, remotes and such. Used to allow quick flashing of multiple ECMs. The nature of the technology means it's usually found on the bigger ($$$$) machines, but it could just as easily be found in any machine. If you find the Product Link ECM on your schematic, you will notice it has Ethernet connectivity although not used in this case. The clicker box was first used alongside ET when CDL was first introduced, but ET and laptop computers were an expensive rarity. I've come across some very early H series graders that used a transmission ECM which pre-dated ET and could only be interfaced through the clicker box, but that's ancient history.
Maybe it is the terminology but I got slightly confused at this point. To me "reference voltage" is not the same as sensor supply voltage. I understand it as a voltage supplied from the ECM on the sensor signal wire that is used to establish the integrity of the sensor signal. It is often referred to as "pull up voltage". I thought that's what you were talking about when you said reference voltage rather than the sensor power supply. We see it often on the forum that people measure the voltage on the signal wire and ask something like "I'm measuring 5v on the signal wire. Is this correct.? Why does it not change when I move the thumb roller.?" In fact all they are doing is measuring the pull up voltage from the ECM. To measure the sensor signal, at least from a PWM-type sensor, requires a DMM capable of measuring duty cycle.
I'm sorry for the confusion. When I said "reference voltage" I meet sensor power supply. Different people call it different things. The way you described it is probable the most accurate. Is that what CAT calls it? A lot of the things I work on of other brands use 5v for sensor supply. It sounds like CAT uses 5v, 8v, and even 12v sometimes. Thank you for explaining "pull up voltage".
Cat generally refers to "pull up voltage" in most of their technical documentation as the voltage used to monitor the integrity of the sensor signal wire. The sensor power supply voltage is usually referred to as exactly that.
Just wait until machines with Single Edge Nibble Transmission sensors begin to make their way into the second hand market. That will really blow your mind.
Can you explain what that is?
Simply put, the sensor is a self contained "processor" which transmits a one way data stream to the ECM. That means sensors can be combined into one unit. For example you could have a combined pressure and temperature sensor.
How would you diagnose that? Is CAT using them on some of their equipment?
Not yet in production machines. Coming in the next generation.
I was wondering if one of you CAT guys could explain the fault code categories of codes on the advanced display to me better. Events: Active: This means that it is happening right now? Stored: This means that it has happened or is happening? Diagnostics: Active: This means that it is happening now? Stored: This means that it has happened or is happening? I know that what I just put is no quite right, but I'm not sure how else to put it. What is the difference between Events and Diagnostics ? I know they are not the same and it seems that some codes show up in one and some in the other.
An Active Event is happening right now. A Logged/Stored Event happened at some point in the past. Ditto the above answer for Diagnostic Codes (to give them their full handle). You can have Active Codes or Logged Codes. Quite simply a Diagnostic Code is generally caused by an electrical/electronic fault, something like a solenoid coil is open circuit or a sensor is misbehaving in some way. An Event can be something caused by mechanical or operational factors (low alternator output or high coolant temp for example), or it can happen as a result of a Diagnostic Code. A classic case of this is the speed sensors on the SSL/CTL/MTL product line. Each sensor housing has two sensors in it and the machine needs both of them working in order to measure ground speed and determine direction of travel. Lose one sensor and speed can still be measured but not direction. As soon as a Diagnostic Code of any type pops up from one sensor an E695 (Unexpected Motor Speed Detection Disabled) Event will pop up as a consequence.
So in your example with the wheel speed sensor would that code come up under diagnostic codes and events?
There would be an Active Diagnostic Code for a wheel speed sensor PLUS an Active E695 Event. Wheel speed sensor Codes are 2685, 2686, 2687, & 2688 depending on which sensor is failed, plus -2, -5, & -8 depending on the failure mode.