2004 CAT 268B aux hydraulic (thumb wheel) issues

[aws32]

Hi guys I’m a new owner of an 1000hr cat 268B. It’s an older machine but it runs great. Has XPS aux hydraulics.

Here is my issue the secondary hydraulic circuit works fine with the buttons on the right joystick, however the primary (hi flow and standard flow) with the thumb wheel do not activate. This machine had the male dual flow connector ripped off and damaged, I replaced the hose, hardline, and dual flow aux connector today. I also tested the thumb wheel by backprobing pins 2 and 3 on the joystick harness. I’m getting a constant 7.82v regardless of thumb wheel position. Also my duty cycle readings just stay at 0% on my meter. I disassembled the hall sensor and attempted to use a neodymium magnet from an old HDD to test and still got the same readings... the oem magnet looks ok. I swapped the connectors on the solenoids and was able to get the circuit to activate using the secondary circuit buttons on the remote, so thinking my thumb wheel switch or aux ECM is toast. What are your thoughts? Nige hoping for a little assistance here before I shell out 1300$ for a joystick!!!

Thanks guys I appreciate your posts and have been reading them diligently.

 

[Nige]

If you’ve been reading diligently then you will know the first requirement is a Serial Number…….

I also tested the thumb wheel by backprobing pins 2 and 3 on the joystick harness. I’m getting a constant 7.82v regardless of thumb wheel position. Also my duty cycle readings just stay at 0% on my meter.

You won’t have any joy measuring duty cycle, that’s only on the later model machines that have a PWM-type sensor on the thumbwheel rather than the magnet that you have. Your thumbwheel switch should output a varying voltage depending on the position of the roller.

Do these five steps and report all your results. With the ley OFF locate the 12-pin wiring harness connector (CONN 33) directly underneath the joystick and unplug it.

1. Turn the key ON and measure the voltage between Pins 1 & 2 (wires P994 Blue & P997 Brown) on the machine side of the connector. It should be 8.0 ± 0.2 volts.
2. Turn off the key and reconnect CONN 33. Turn the key on and measure the voltage again between Pins 1 & 2 by back-probing into the connector. Confirm that it is the same as measured in Step 1.
3. With the key ON and the thumbwheel in the centre measure the voltage between Pins 3 & 2 (wires P996 Green & P997 Brown) by back probing at CONN 33.
4. Repeat Step 3 with the thumbwheel rolled all the way forward.
5. Repeat Step 3 with the thumbwheel rolled all the way back.

Post the results from Steps 1-5 back here.

 

[aws32]

My apologies, here is the serial

*CAT0268BJLBA00354*

Will reply to your troubleshooting steps later today. Thanks again.

 

[aws32]

1. 174mV
2. Same as 1
3. 7.54v
4. Same as 3
5. Same as 3

 

[Nige]

1. 174mV
2. Same as 1

In that case you are missing the 8v supply to the thumbwheel roller. Get that back and things might just work.

3. 7.54v
4. Same as 3
5. Same as 3

That's not the thumbwheel output. You're measuring the pull-up voltage coming back along the signal wire from the ECM.

Find the AUX ECM and unplug the 70-pin connector. First inspect it for green crusties on the pins/sockets of both the ECM and the harness connector.

You will then need to unpin three wires from the connector, P994-BU, P996-GN, & P997-BR. These are on Pins 60, 53, & 52 respectively. Once the wires are unpinned plug the connector back into the ECM.

Then turn the key ON and backprobe between Pins 52 & 60 of the connector to see if you get the correct 8.0 ± 0.2 volts output supply to power the thumbwheel. If you don't then the AUX ECM is toast.

 

[aws32]

Thanks! I will overnight a depinning tool and let you know my findings. Can you de-pin without a tool?

On another note - is it possible to disable the aux hydraulics via programming the ECMs with ET? Wondering if maybe it was reflashed when the aux circuit was damaged to prevent accidental triggering and subsequent loss of fluid/contamination?

 

[Nige]

Can you de-pin without a tool?

Not AFAIK, certainly not without running the risk of damaging the pins anyway.
The Deustch de-pinning tools are not expensive, a couple of $ at the most. Get more than one, they only plastic and are easy to break. Just need to get the correct size. I think from memory it's the pale blue one for 16-20 SWG wires.

See here........... https://www.deutschconnector.com/products/deutsch_connector_tools/deutsch_connector_removal_tools/

is it possible to disable the aux hydraulics via programming the ECMs with ET?

Again AFAIK, the AUX function is not a parameter that can be enabled/disabled using ET.

 

[aws32]

Thanks again Nige, I was on vacation last week and finally got back to diagnosing - I did not get ~8v after unpinning. I've ordered a replacement reman ECM and they are programming it to my serial #, hopefully it works as CAT dealer want's about 5k for a reman! Should be here in about a week or so, if it doesn't work I can return it.

Also wondering if this could be related - I noticed that earlier today my seat-belt light was lit very dimly. I wiggled the connector going to the high flow switch (and the switch itself), and then the seatbelt / lap bar lamp slowly went out. It hasn't done this since I put it all back together and cycled the key, lap bar and parking brake in my testing. Could be coincidence, but are there any other ECM inputs I should be looking for, what about specific relays? I also bypassed the high flow switch by jumping pins 2 and 3 and still didn't hear any solenoids engage.

The secondary aux circuit seems to be working fine, is this circuit also controlled via the aux ECM?

 

[Nige]

Also wondering if this could be related - I noticed that earlier today my seat-belt light was lit very dimly. I wiggled the connector going to the high flow switch (and the switch itself), and then the seatbelt / lap bar lamp slowly went out.

The lap bar switch and seat switch (if equipped) are inputs to the Interlock ECM that controls machine operation from a safety aspect.

The secondary aux circuit seems to be working fine, is this circuit also controlled via the aux ECM?

It is, but it is quite possible for one circuit of an ECM to be bad and the rest of it to be functional.

 

[aws32]

Hi Nige - I replaced the ECM and now am getting the following readings.

1. 10.64v
2. Same
3. 5v
4. 2.42v
5. 8v

I still cannot get the auxiliary hydraulics to work.

Relays seem good, however the diodes in the fuse box do not give me a reading in either direction on my meter? Maybe I’m not testing them correctly, but I’ve ordered some new ones thinking this is also a problem?

 

[Nige]

1. 10.64v
2. Same

Your replacement ECM is apparently bad. Where did you source it.?
The voltage between Pins 1 & 2 should be 8.0 +/- 0.5v.

 

[aws32]

Your replacement ECM is apparently bad. Where did you source it.?
The voltage between Pins 1 & 2 should be 8.0 +/- 0.5v.

Sourced it from an Amazon seller that we have successfully used in the past for equipment ECMs. Maybe they flashed the incorrect file… maybe the voltage regulator is shot… are the signal voltages too high? Shouldn’t I be seeing some type of response from the machine? Looks like the wiring and joystick checks out at this point, so that’s a relief. I don’t know too much about CAT machines, thanks for your assistance.

 

[Nige]

Maybe they flashed the incorrect file…

I wouldn't have thought that would have any bearing. The hardware rather than the software is what creates the sensor supply voltage.

Looks like the wiring and joystick checks out at this point, so that’s a relief.

Have you tried applying 12v direct to the AUX solenoids on the main control valve to see if they function.? That would at least prove they are working.

 

[aws32]

Have you tried applying 12v direct to the AUX solenoids on the main control valve to see if they function.? That would at least prove they are working.

Yes I swapped the harness for the secondary aux circuit (I think c1/c2, the official cat docs call everything c+/c-) to the primary and using the push buttons on the right joystick the solenoids open and fluid flows.

I’ve contacted the seller hopefully they can send me a new ECM. Is there any other reason my voltage would be high with machine off key on?

 

[Nige]

I’ve contacted the seller hopefully they can send me a new ECM. Is there any other reason my voltage would be high with machine off key on?

Not AFAIK. Between Pins 1 & 2 with key OFF should be zero. Key ON it should be 8.0 +/- 0.5v.

I swapped the harness for the secondary aux circuit (I think c1/c2, the official cat docs call everything c+/c-) to the primary and using the push buttons on the right joystick the solenoids open and fluid flows.

Based on what you have done so far the only other thing I can think to check would be the actual wiring between the ECM and the AUX solenoids. By doing the bypass the way you did that wiring was not used therefore its functionality is still open to question. Box-ticking basically.