Als

1769-L33ER Processor not Talking to I/O Modules

21 posts in this topic

Hi there,

I have 1769-L33ER Allen Bradley processor suddenly stopped running the plant. No indication of faults. Processor running okay with OK and Run LEDs on. Did all basic troubleshooting steps but the issue still exist and I cannot run the plant. Connected on line and checked no faults exists in Fault Table.

I did some simulation and found that Processor is not talking to the I/O modules.

What could be the problem?

 

Thanks for your help.

Edited by Als

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Is the processor's "I/O Ok" light solid green?  What do you mean by "did some simulation" ?

Look at the connection status in each I/O module's popup window.

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Processor's "I/O OK" light is blinking green. Simulated by sending 4-20mA from field via process meter, not getting any change in values. Sending 24vdc in for discrete inputs, no activity in logic.

Just checked I/O configuration tree and realized processor lost communication with all I/O modules. Will check physical connections and I/O config settings as well. 

Is there any other possible causes for this I should look at?

Thanks so much for your help.

 

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In the connection tab of the modules' configuration pages, the connection tabs should show live indicators and error codes.  Screenshot them for use to review.

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Thank you. Please review screenshot attached. The Module connection fault is the same for all I/O modules.

 

 

Capture.PNG

Edited by Als

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What version of Logix 5000 are you using? Is your computer  a 32 or 64 bit? 

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Am using Version 30.011 of Studio 5000. My Process Laptop is 64 bit.

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Was this running before then stopped or is this a new setup?

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We upgraded from SL5/05 running on RSLogix500. It has been running for about 2 years now. This just happened in the middle of the machine doing its normal cycle.

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The CompactLogix 1769 Bus is a DeviceNet Bus that runs card to card through side to side connections.

It is not uncommon for the Bus Connections to corrode over time and cause issues of this type.

First troubleshooting step is almost always to power down the unit, seperate all the modules on the din rail carefully and then re-seat them.

 

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Have you tried cycling power to the rack or downloading your program to it again?

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I did cycle the power. Moved mode selector switch on the processor from Remote to Program then to Run and back to remote. Run and Ok LEDs solid green but I/O Ok LED is blinking green and thus issue not resolved. 

I totally powered down the unit, carefully separated the modules, inspected the cards and all connector pins in good condition. Carefully reseated them back and powered up. repeated the steps for mode selector switch. Still no luck as yet.

Unfortunately, I don't have a up to date back file that I can reload.

Thank you,

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49 minutes ago, BobLfoot said:

It is not uncommon for the Bus Connections to corrode over time and cause issues of this type.

Or just wiggle loose.  I endorse Bob's advice.

If that doesn't work, you may have CPU hardware failure.

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35 minutes ago, Als said:

Unfortunately, I don't have a up to date back file that I can reload.

You were online with that processor.  Surely you can save a copy while online.

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If that does not work, in my experience this is usually firmware corruption. If you have communications to the processor try reflashing the firmware to the same version then download your program to it again. I have had this happen to me on a 5/05 processor and it was the firmware. This might not work, but is worth a try. 

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Yes, I did save a copy but that was when the issue came up. Can I reload that same project file again?

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37 minutes ago, Otto Automation said:

If that does not work, in my experience this is usually firmware corruption. If you have communications to the processor try reflashing the firmware to the same version then download your program to it again. I have had this happen to me on a 5/05 processor and it was the firmware. This might not work, but is worth a try. 

Thank you. Will give it a try.

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This is the general layout of the modules in the panel. Thought of CPU failure but I saw on the I/O configuration pane, processor has active communication with two other units over ethernet. Only the I/O modules that the processor has lost communication with.

Capture.PNG

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12 hours ago, Als said:

Thought of CPU failure

Yeah, but the CPU can have a failure in just its backplane circuits.  Or, since a CompactLogix doesn't have an independent backplane that isolates failures to single devices, any one of your "backplane" modules could be shorting out the comms.

Independent of the ethernet.

Take your backplane apart.  Put it back together one module at a time, testing with the end cap for each module added.  If you find a failure point, swap the order to confirm which module is the problem.  If you can't get any backplane module to work with that CPU, the CPU's backplane circuit is broken.

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Hello All,

Thank you all for directing me towards resolving this very critical issue. Carefully following through your directions, I identified the faulty module, which was the Modbus TCP/IP Communication module (MVI69-MNET) on slot#12. Since nothing was connected to it, I simply removed the module and reset the processor.

PLC is up and running now with no issues. Plant has been running now for the last 2 day. 

 

This is a great forum with great people. 

Thank you.

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Your earlier picture shows the MNet module is already inhibited, so good call on removing it.

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