CAT304E Auto Idle Issue

[jzampieron]

Hi, Have an interesting issue with my CAT 304.

The auto-idle, which used to work with all the controls, now only works with the travel levers, but not the sticks or the blade lever.
When moving the joysticks or blade lever the machine stays at idle.

Hydraulically, all the controls work. I did find a disconnected sensor (I think its a sensor) connected to the hyd. manifold and reconnected it, but that didn't resolve the issue.

I checked the fuses and relays and they all appear good.

I disconnected the battery for a few minutes to see if the ECM needed a reboot, but that didn't help either.

Thoughts? All the other connectors and wires I could find seem right and tight.

 

[ahart]

What’s the serial number of your machine?

 

[jzampieron]

CAT0304EETTN01304

 

[jzampieron]

Does anyone happen to have the schematics handy for the 304E-CR? If not, I'll probably bite the bullet and get the full service manual from the dealer when I put a thumb on the machine.

 

[ahart]

I have access and if nige doesn’t come along and send them, I will try tomorrow. Can you get into the monitor and see if you have any active codes? The book doesn’t specifically say what reference it uses for the auto idle function to know when a function is activated and I haven’t came across one that didn’t work before now.

 

[heymccall]

Bad pilot pressure switch (or wiring).
Looking now for it.

 

[ahart]

I did find a pressure switch part number 362-3225 for pilot and travel that signals the governor to control the auto idle. Can you confirm what was unplugged?

 

[Nige]

To the OP. Schematics sent. Check your messages.

I did find a pressure switch part number 362-3225 for pilot and travel that signals the governor to control the auto idle. Can you confirm what was unplugged?

#3 in the illustration below.

 

[jzampieron]

That looks like it. I've attached a photo. Last night I disconnected again and metered the switch. It appears to be a simple pressure threshold contact closure.
When I actuated the blade the switch went from open to closed, so I'm 99% sure the pressure switch is good.

What's more concerning to me is that I don't meter out any appreciable voltage on the other side of the connector. Usually those things are pulled high (12V, 5V, 3.3V, whatever) at the ECM and then ground-out when the switch closes to the ECM.
I'll review the schematics tonight and try to chase out where the other end of that connector goes.

Open to other ideas.

 

[ahart]

Schematic shows the switch makes continuity to ground when it’s closed, what concerns me is it works with travel but not with implement movement. I’ll keep looking for the connection between the two.

 

[jzampieron]

Pretty sure its a broken wire on circuit "H476". I don't get continuity between the white wire on the sensor and ECM Pin 36. Still chasing it.

 

[Nige]

Doncha just love schematics..?

 

[jzampieron]

SOLVED!

Really do. Was able to separate CONN 9 in the battery box, Buzz out Pin 1 on both sides. The cab harness (CONN9-Female to ECM) was good. The chassis harness (CONN9-Male to AEC) was no good, open.
Wasn't able to find a break and not going to try to get at that.
Ran a new wire from the sensor to the CONN9-Female Pin 1 wire.

Everything is fixed and Auto Idle works as expected.

Thanks for the assistance!