Iwaki Pump Error Codes: EHN Display Messages, Alarms and Resets

Iwaki pump error codes are not what most buyers expect. If you are searching for an E01 or E02 list for an IWAKI EHN solenoid metering pump, you will not find one, because the EHN series shows status messages instead of numbered faults. STOP, -STOP, OVER, a keypad lock mark and, on YN models with the FCM flow detector, an alarm sequence. This guide is written for plant operators, OEM skid builders and distributors who need to read those messages fast. Everything here follows the EHN-R and EHN-YN instruction manuals. For other Iwaki series, check the manual for that exact model.

Iwaki pump error codes: display messages vs real faults

The EHN digital screen mostly reports what the pump is doing. The LED stays on while the pump waits and blinks once per stroke while it runs. Most text on the screen is a state, not a failure, and that is why Iwaki pump error codes are easy to misread.

Real hardware faults behind Iwaki pump error codes, such as a failed control unit or a broken diaphragm, usually have no dedicated code at all. So it helps to split troubleshooting into two tracks. One track reads the screen. The other reads what the pump is physically doing.

Common Iwaki pump error codes on the EHN screen

Here are the Iwaki pump error codes you will see most often on site, with the usual fix:

STOP or -STOP: a signal is present on the STOP terminal. The pump is either paused mid-run or held in a manual wait state. It resumes when the signal clears. Check the level switch and its wiring.
.0: the pump is in EXT mode with the E-SP display option and is waiting for external pulses. Check the flow meter and the pulse cable.
OVER: in EXT mode the incoming signal asks for more than the upper limit. The pump will not run faster than the MAN speed, and excess pulses are stored. Raise the MAN speed or reduce the multiplier.
Keypad lock mark: every key is ignored. Hold the START/STOP key for about three seconds to release it.

You may also see T-5, T-10 and T-50 (anti-chattering time for pulse reading), /5 and X5 (divisor and multiplier) and M-OF or M-ON (STOP logic). These are settings, not Iwaki pump error codes or alarms. Seeing them typically means someone is in the programming menu.

A keypad lock trap during emergencies

With the keypad locked, the only emergency stop is cutting main power, and the keypad is still locked after power returns. The manual also warns you to stop the pump with the key and wait about three seconds before unplugging it. Otherwise the last stop command may not be saved, and the pump can start dosing on its own at the next power-up.

How to reset Iwaki pump error codes properly

Do not try to clear STOP messages by cycling power. If the external signal is still there, the pump stops again. Go to the source instead. Refill a low tank, clean a float switch stuck with crystals, and if a normally closed switch was fitted recently, confirm M-OF and M-ON are not reversed. Under M-ON logic the pump stops when the signal drops, which confuses a lot of technicians. Our Iwaki STOP release guide walks through each case.

OVER is one of the Iwaki pump error codes that does not need a reset. It only tells you the pulses are arriving too fast. If it shows up all the time, the MAN speed is usually set too low or the multiplier too high, so recheck the process numbers.

FCM alarms: Iwaki pump error codes on EHN-YN models

The YN model adds FCM flow detection. The FCM sits below the pump inlet. If no suction flow is seen within the PA (pre-alarm) time, the pump runs at full speed, 360 spm, to try to break the air lock. If flow still does not return by the end of the AL (alarm) time, the pump stops and sends an alarm output. PA, AL and RE times are each adjustable from 1 to 60 minutes, or can be switched off with PAOF, ALOF and REOF.

The manual says not to set the AL time above 30 minutes, since long dry running damages the pump. After an FCM stop, fix the suction side first: an empty tank, air leaking into the suction line or a blocked foot valve. Then press START/STOP to return to the wait state. For air lock and the auto-degassing head, see Iwaki EHN not dosing and auto degassing.

Faults that show no Iwaki pump error codes

Most entries in the manual's troubleshooting table have no screen message:

No run, LED off, blank screen: voltage outside the 90–264 VAC range, no power, broken wiring or a failed control circuit.
Cannot prime: air lock in the head, stroke length too short, air entering the suction line, a valve set installed upside down, missing valve gaskets or a stuck valve ball.
Flow fluctuates: air left in the head, overfeeding (fit a check valve), a broken diaphragm or unstable pressure at the injection point.
Leaks: loose fittings or air vent body, a loose pump head, missing O-rings or excessive discharge pressure.

One more point that matters for skid builders. If a voltage signal is applied to the EXT or STOP terminal by mistake, the control unit can fail and must be replaced. Power down before wiring, and use dry contacts or open collector outputs only.

Conclusion

For the EHN series, Iwaki pump error codes are really a list of status messages. STOP and -STOP point to an external signal, OVER points to pulse rate versus MAN speed, the keypad lock clears with a three second press, and FCM alarms on YN models start at the suction side. Blank screens, priming problems, flow swings and leaks have no code, so work through the symptom list instead. For other Iwaki models, the meaning of each message depends on that model's manual. To adjust parameters, see EHN control panel settings. For spare parts and replacement pumps, browse the Iwaki brand page or our solenoid metering pumps. Not sure what your screen is telling you? Send the model plate and a photo of the display through our contact page and our engineers will help.

FAQ

Do Iwaki pump error codes include numbers like E01?

Not on the EHN series. It shows status words such as STOP, OVER and a lock mark, so check the manual for other series.

Why does my Iwaki pump show STOP when the tank is full?

Usually the float is stuck or the STOP logic is reversed. Free the float, then check the M-OF and M-ON setting.

None of the keys respond. Is the control board dead?

Usually it is just the keypad lock. Hold START/STOP for about three seconds and the keys work again.

How do I reset an FCM alarm on an EHN-YN pump?

Fix the suction problem, such as air ingress, an empty tank or a blocked foot valve. Then press START/STOP to restart.

Where can I find Iwaki pump error codes for other series?

Look in the instruction manual for that exact model, since messages differ between series. Our team can also check it for you.