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JACK A4, K4, A5 Error Codes: Complete Err-01 to Err-23 List
Quick Answer
JACK’s A4, K4, A5, ZB-A4F, and ZB-A2S machines are the auto-trimmer, direct-drive lockstitch line, and they share a different control box family from the F4/F5/F6 range — instead of single-letter codes like E1 or E6, they show two-digit “Err-XX” codes on the panel. Across these models we found 19 documented codes: Err-01 through Err-18, plus Err-23. This guide explains what each JACK Err-XX error code means and how to fix it, sourced directly from JACK’s own A4, K4, A5, ZB-A4F, and ZB-A2S operation manuals, plus JACK’s own official maintenance videos. Jump to your code below, or read through for the full picture.
What Are JACK Err-XX Error Codes?
The A4, K4, A5, ZB-A4F, and ZB-A2S are JACK’s auto-trimmer direct-drive lockstitch machines — the “auto-trimmer” part matters, because these models have an extra thread-trimming solenoid and encoder that the plain F4/F5/F6 range doesn’t, which is why their control box needs more fault codes to cover more moving parts. Not every model shows every code — a given machine will only display the errors relevant to the parts it actually has (a K4 might never show a code that only applies to a feature on the A5, for example).
These “Err-XX” codes are a completely separate numbering scheme from the E1–EZ codes used on JACK’s F4, F5, and F6 machines — covered in our separate F4/F5/F6 guide. If your control panel shows a single letter-plus-digit code like “E4” rather than “Err-04”, you’re on the F-series scheme, not this one.
JACK Err-XX Error Code Chart: Err-01 to Err-23
| Code | What It Means | Quick Fix |
|---|---|---|
| Err-01 | Hardware over-current | Restart, check voltage, check for stuck mechanical parts, check motor plug |
| Err-02 | Software over-current | Restart; if it repeats, reduce load and check wiring |
| Err-03 | Under-voltage | Check supply voltage is within the rated range |
| Err-04 | Over-voltage while the machine is switching off | Check supply voltage isn’t spiking on shutdown |
| Err-05 | Over-voltage during operation | Check supply voltage stays within rated range while running |
| Err-06 | Short circuit in the trimmer solenoid | Inspect the auto-trimmer solenoid and its wiring |
| Err-07 | Motor current-measuring circuit failure | Power-cycle; contact a technician if it recurs |
| Err-08 | Sewing motor blocked (motor stalled) | Check for a jammed head, thread wrap, or bent needle |
| Err-09 | Brake circuit failure | Check the brake circuit and control box connections |
| Err-10 | Communication failure (panel/HMI to control box) | Reseat the panel cable, restart |
| Err-11 | Needle positioning failure at the machine head | Check the needle-position sensor and its plug |
| Err-12 | Initial motor electrical angle detection failure | Restart; contact a technician if it repeats |
| Err-13 | Motor Hall sensor failure | Check the Hall sensor plug and wiring |
| Err-14 | Control board EEPROM read/write failure | Restart; may need a technician to reset or replace the board |
| Err-15 | Motor over-speed protection triggered | Restart; check the speed parameter setting |
| Err-16 | Motor reverse rotation detected | Restart; check motor wiring phase |
| Err-17 | Panel (HMI) EEPROM read/write failure | Restart; may need the panel reset by a technician |
| Err-18 | Motor overload | Check fabric weight, lubrication, and for mechanical resistance |
| Err-23 | Motor blocked with encoder failure | Check the encoder connection in addition to clearing any jam |
Not every model displays every code above — the ZB-A4F manual, for example, only documents Err-01, 03, 04, 05, 06, and 07, while the fuller A4 and K4 manuals list all the way to Err-18 and Err-23. Some K4 control boxes also show three unnumbered alerts: a power-off alarm, a trimming-cutter safety-switch alarm, and a sleep-mode (“dormancy”) indicator.
The Most Common JACK Err-XX Codes Explained
Err-01 & Err-02 — Hardware and Software Over-Current
These are the two most-reported Err codes, and both mean the control box detected more current than it expects, either from a hardware sensor (Err-01) or its own internal calculation (Err-02). Power off, wait a minute, and restart. If it repeats on the same fabric, check whether the machine is jammed, under-lubricated, or being asked to sew material that’s too heavy for the setup.
Err-03, Err-04 & Err-05 — Under-Voltage and Over-Voltage
All three point to the incoming power supply rather than a worn part: Err-03 is under-voltage, Err-04 is over-voltage as the machine switches off, and Err-05 is over-voltage while running. Check the supply voltage against the machine’s rated range before assuming anything mechanical is wrong. A voltage stabilizer is the usual long-term fix where mains supply fluctuates through the day.
Err-08 & Err-23 — Motor Blocked / Stalled
Err-08 means the sewing motor is stalled, and Err-23 is the same fault with an added encoder failure on top. Turn the hand wheel by hand first — if it’s stiff or won’t move, clear the mechanical jam (thread wrap, bent needle) before checking anything electrical. If the hand wheel turns freely, the fault is more likely in the motor’s drive coupling or its Hall sensor.
Err-11 & Err-13 — Needle Position and Motor Hall Sensor Faults
Err-11 and Err-13 both come from the sensors that track needle and motor position — Err-11 at the machine head, Err-13 at the motor itself. Check that the sensor plug is fully seated and the wire isn’t frayed or pinched. A worn wheel sensor is a common repeat cause of both.
Err-15 & Err-16 — Motor Over-Speed and Reverse Rotation
Err-15 fires when the motor exceeds its safe speed limit, and Err-16 fires when the motor is detected spinning in reverse. Restart the machine first; if either code returns under normal sewing speed, the speed parameter setting or motor wiring phase needs checking by a technician.
Err-14 & Err-17 — EEPROM Read/Write Failures
Err-14 is a fault on the control board’s memory chip, and Err-17 is the same kind of fault on the display panel’s memory chip. Both usually need a technician to reset or reflash the board — this isn’t something a plug reseat typically fixes.
Err-06, Err-07, Err-09, Err-10, Err-12, Err-18 — Other Solenoid, Brake & Communication Faults
The remaining codes cover more specific faults: Err-06 is a short circuit in the auto-trimmer solenoid, Err-07 is a motor current-measuring circuit fault, Err-09 is a brake circuit failure, Err-10 is a communication failure between the panel and control box, Err-12 is an initial motor electrical-angle detection fault, and Err-18 is general motor overload. Reseating the relevant plug and restarting clears most of these; if not, they usually point to a control-board-level fault worth a technician visit.
Preventing Repeat Err-XX Faults
- Reseat and inspect the motor, encoder, and trimmer-solenoid plugs during routine cleaning — connector faults (Err-01, Err-08, Err-11, Err-13) are the most common repeat offenders
- Keep the machine oiled on schedule to avoid overload-type codes (Err-02, Err-18)
- Turn the hand wheel by hand before assuming an electrical fault on Err-08 or Err-23 — a mechanical jam looks identical to a sensor fault until you check
- Use a voltage stabilizer if your workshop’s mains supply fluctuates, to cut down on repeat Err-03/04/05 trips
Genuine Spare Parts for JACK A4/K4/A5 Fixes
The same electronics parts that fix F4/F5/F6 faults apply here too, since JACK’s auto-trimmer models use compatible sensors and control boards:
- JACK Wheel Sensor — fixes recurring Err-11/Err-13 position faults
- JACK Wire Connector — fixes intermittent Err-01/Err-08 connection faults
- A2B PCB Motherboard — for board-level Err-14/Err-17 faults
- Direct Drive Servo Motor Control Board — universal-fit control board option
- Direct Drive Wheel — for Err-08/Err-23 motor-stuck issues
Frequently Asked Questions About JACK Err-XX Error Codes
What does Err-01 mean on a JACK A4 or K4 sewing machine?
Err-01 means the control box detected a hardware over-current fault. Restart the machine after checking that nothing is mechanically jammed and that the motor plug is properly seated.
Why does my JACK auto-trimmer machine show Err-08?
Err-08 means the sewing motor is stalled or blocked. Turn the hand wheel by hand first to rule out a mechanical jam before assuming the motor or its sensor has failed.
Is Err-XX the same as the E1/E4/E6 codes on a JACK F4 machine?
No. Err-XX two-digit codes belong to JACK’s auto-trimmer control box family (A4, K4, A5, ZB-A4F, ZB-A2S). The F4, F5, and F6 use a separate single-letter scheme (E1 through EZ) — see our F4/F5/F6 guide if that’s what your panel shows.
What is a Hall sensor fault (Err-13) and can I fix it myself?
The Hall sensor tracks the motor’s position electronically. A loose or damaged plug is a straightforward fix you can check yourself with the machine unplugged; if reseating the connector doesn’t clear Err-13, the sensor itself likely needs replacing.
Related guides: JACK F4/F5/F6 Error Codes Guide | JACK vs Juki Buying Guide | JACK Wheel Sensor
Written by Aashu, owner of Stitch Partner. We source and fit genuine JACK spare parts every week — this guide reflects the Err-XX codes and fixes we actually see, cross-checked against JACK’s own control box manuals and official maintenance videos.
