The C/Q line (pin 4) on one IO-Link port is overloaded or shorted. C/Q carries IO-Link data, or works as a digital input or output, so the sensor or load on that pin is not being driven properly.
| At a glance |
|
| Code |
611 |
| Shown as |
IO-Link C/Q Overload |
| Severity |
Warning |
| Category |
6xx — Hardware |
| Raised for |
Each port on its own — IO-Link Port A or IO-Link Port B |
| Clears |
Automatically, 3 seconds after the overload stops |
| LED |
Health light shows the warning. The Power light does not change. |
New in an upcoming firmware update. Earlier firmware does not raise this alarm.
- Waits two seconds. When the controller looks for an IO-Link sensor it sends a short wake-up pulse that briefly runs C/Q into its current limit — that is normal, even on an empty port. Only an overload that lasts 2 seconds raises this alarm.
- Raises this alarm for that port.
- Keeps going. C/Q is current-limited to 500 mA and recovers on its own. The port’s 24 V supply (L+) stays on.
- Clears the alarm by itself once the overload has been gone for 3 seconds.
The Power light stays as it was: it reports supplies only, and C/Q is a signal line.
| Cause |
What to look for |
| C/Q shorted in the cable |
Pin 4 (black) touching pin 1 or pin 3 — a damaged cable or a miswired field connector. |
| Too much load on a C/Q output |
C/Q set as a digital output and driving a relay coil, solenoid, or lamp that draws more than it can supply. |
| Wrong kind of device |
A device that drives pin 4 itself, wired to a port that is set as an output. |
| Failed sensor |
The fault moves with the sensor to the other port. |
- Find the port. The alarm names it — IO-Link Port A or B.
- Check what C/Q is set to on the port screen — see Configuring a port. If it is an output, check what it drives: switch a heavy load through an interposing relay, not directly from C/Q.
- Unplug the device. If the alarm clears, the fault is in the device or its cable.
- Try a known-good cable, then try the device on the other port.
- If the port faults with nothing plugged in, contact support.
- This is the signal line, not the supply. A short on the 24 V sensor supply is IO-Link Supply Short (610), which also cuts the supply and changes the Power light.
- An IO-Link sensor may drop while this is active, because its data line cannot be driven. Expect Device Disconnected (100) alongside it.