When an HMI panel shows an error code such as 0x0002, the panel itself can name the tag behind it: hold the upper-left corner of the touch screen for 3 seconds to open the System Screen, then read the Error tab. Match the printed tag to the exact project reference, correct only that reference, and retest until the tab stays clear.
When an HMI panel throws an error code such as 0x0002, the code on the screen is half the diagnosis. The panel keeps the other half in its own error log, and that log names the tag behind the fault. You reach it from the touch screen: hold the upper-left corner of the screen for 3 seconds and the System Screen opens, with an Error tab that lists each fault and the tag that raised it. Read that name, match it in your project, and you edit the one reference that is wrong instead of hunting through every tag in the project. This article walks through the procedure, what the entries point to, and how to confirm the fix, all from the panel's own diagnostics before any project edit.
The answer: the Error tab on the System Screen
On this panel family the way in is a touch gesture. Hold the upper-left corner of the screen for 3 seconds and the System Screen opens. Select the Error tab. Each entry there carries the error code and the tag information behind it, which is why the tab is the place offending tags are listed.
Record the code and the tag exactly as printed before you leave the screen, character for character. A code such as 0x0002 narrows the fault to a class, for example an address problem, and the panel maker's error-code table explains the class. The tab turns the class into a name: it tells you which tag raised the fault, and that name is what you take into the project.
What each symptom points to
- The code shows on the running screen and no tag with it. The alarm banner prints the class of fault only. The tag sits in the log, so open the System Screen and read the Error tab.
- The Error tab lists the entry with a tag name. That exact name is the reference to check. Read it character for character; a tag with a similar name is a different tag.
- The Error tab lists communication entries instead of a tag. The fault sits in the link between the panel and the controller, and the timing of the entries tells you where to start. Fixing an HMI protocol error that pops up every 30 seconds covers that path.
- The Error tab is empty while the code still shows. Confirm you opened the System Screen on the panel that produced the error and on the screen set the operator was running. Capture the exact printed text if the code repeats.
Example: a fill station shows code 0x0002
A packaging line's fill station drops to a fault screen. The banner prints 0x0002 and nothing else. The operator was on the tank level screen, so the fault is tied to something that screen reads.
You hold the upper-left corner for 3 seconds. The System Screen opens and the Error tab lists one entry: code 0x0002 against the tank level tag. The entry names the tag, so the search in the project goes from every tag down to one.
For this panel family, the maker's published error-code table lists 0x0002 as address out of range, and the documented remedy is to check that the tag name and the System ID match on both sides, in the panel project and in the controller programming software. You open the project, pull up that one tag, and find its controller address does not match the address the controller program maps for the tank level. Save a copy of the project, correct the address so both sides agree, and transfer the revised project with the normal transfer workflow.
Retest: reopen the Error tab and run the fill station through its filling step three times. The tab stays clear and the level value tracks on the screen, so the fault is closed. The tally: one 3-second hold, one entry read, one reference corrected, three clean cycles.
Checks before you edit anything
- On the panel that showed the fault, hold the upper-left corner for 3 seconds and open the System Screen.
- Open the Error tab and write down the code and tag exactly as printed.
- Search the project on the PC for that exact tag string. Accept an exact match only; a similar name is a different tag.
- Open the same tag in the controller programming software and compare the address and the System ID on both sides.
- Save a copy of the project first, so the original state stays on file.
The fix: correct the reference and retest
Edit the reference the tab confirmed and nothing else in that pass. Extra cleanups mixed into the same transfer make the retest ambiguous, because you lose track of which change cleared the entry. Transfer to the panel you noted, with the installation's normal transfer workflow. The transfer-complete dialog is the delivery report; whether the reference is now valid shows up in the Error tab.
After the transfer, hold the upper-left corner again for 3 seconds, reopen the Error tab, and run the machine step that raised the fault three times. If the tab stays clear and the values track, the fix holds. If a new entry appears, record the code and the tag it names and continue from that entry. Each pass reads the panel's report first, so the loop ends when the tab is quiet.
Two follow-ups cover the common leftovers. To watch the corrected value settle without reopening the System Screen, many panels serve current tag values to a browser on the same network, and reading PLC tag values from an HMI panel web server shows the setup. If the fault is gone but the value updates late, that is a separate delay in the chain, and finding where an HMI display lags behind PLC values shows where to measure it. When the panel itself is healthy and the line needs a separate notice or andon-style status board built from the same data, that is a different screen doing a different job, and the shop-floor screens category covers what those units are made for.
Recommendation: read the tag from the panel before you edit anything. On the panel that shows the fault, hold the upper-left corner for 3 seconds, open the Error tab, and record the code and tag exactly as printed. Match that name to the exact project reference, compare the address and the System ID on both sides, save a copy of the project, and correct only that reference. After the transfer, run the faulting step three times and re-check the tab. If the tab prints no tag on the affected panel, stop editing and take the exact error text, the panel model, the project backup and the controller program to the panel maker's support channel.
Questions
The same tag faults again a week later. Why?
An address that was correct can stop being correct. If the controller program was edited, downloaded or replaced since your last fix, the mapped address may have moved, and the panel raises the same code on the same tag. Re-run the same sequence: hold the upper-left corner for 3 seconds, read the Error tab, and compare the current reference against the project copy you saved before the first edit.
Do HMI error codes mean the same thing on every panel?
Codes are assigned per panel family, so read a code against the error-code table published for your model. In one common family's published table, 0x0002 means address out of range, and the documented remedy is to confirm the tag name and System ID match in both the panel project and the controller programming software. Another maker can assign 0x0002 to a different fault, which is why the Error tab, not the code, names the tag.
Where does the browser find the panel's tag values?
At the panel's own IP address on the same network. Type the panel's IP into a browser on a PC connected to the same network and the built-in web server serves the current tag values. If the panel gets its address over DHCP and you are not sure which address it took, read it from the panel's own setup screens instead of guessing.
Planning information, not legal or engineering advice. Rules differ by place: check codes and permits with your local authority and your licensed trades.