Yaskawa GA800 E42 Fault — What It Means
E42 does not appear in published GA800 VFD fault code lists. In Yaskawa’s documentation family, E42 is a servo alarm code that means a feedback or encoder communications problem on the encoder-side wiring or connector. If you see E42 on a GA800 display, the fault is most likely coming from a connected encoder feedback device, option card, or servo axis rather than the drive itself. The alarm points to a contact fault at the encoder connector or incorrect encoder wiring, not a power-stage failure.
Because this code is tied to encoder feedback circuitry, the first step is to confirm whether your GA800 system uses an encoder option or feedback module. If it does, the fault means the drive cannot communicate reliably with that encoder. If your GA800 does not have encoder feedback, verify the exact alarm code in your installation manual, because the number may be misread or the device may be a different Yaskawa product family.
Before You Replace Anything
Technicians sometimes replace the encoder or the drive itself before checking the connector. Re-seat the encoder connector and inspect the cable for damage first, which costs nothing and clears most E42 alarms.
Common Causes
- Loose or oxidized encoder connector The encoder plug is not fully seated, has corroded pins, or the latch is not engaged, breaking the feedback signal path.
- Incorrect encoder wiring or pinout Wires are swapped, open, or shorted, or the cable does not match the encoder and option manual pinout.
- Damaged encoder cable conductors or shield The encoder cable has crushed conductors, a broken shield, or internal opens from flexing or vibration.
- Noise or grounding problems on feedback wiring The encoder cable is routed near high-power conductors or welding equipment, or poor grounding allows noise to corrupt the feedback signal.
- Failed encoder or feedback option module The encoder itself or the feedback option card has failed internally and cannot send valid signals even when wiring is correct.
- Failed drive feedback input circuitry If all external parts test good, the encoder input circuit on the drive or servo amplifier may be damaged.
Quick Diagnosis
Answer these to narrow it down fast.
Does your GA800 system have an encoder or feedback option installed?
No: Verify the exact fault code in your GA800 manual, because E42 is not a standard GA800 power-drive fault and the code may be misread or the device may be a different Yaskawa model.
Does the encoder connector click fully into place and show no bent pins or corrosion?
No: Clean the connector, straighten pins if safe to do so, and re-seat firmly. Many E42 alarms clear at this step.
Does the alarm clear after re-seating the connector and power cycling the drive?
No: The problem is in the cable, encoder, option module, or drive feedback input. Verify wiring pinout, check cable continuity, and substitute the encoder or option card.
Step-by-Step Fix
- Stop the machine safely and lock out power to prevent motion during diagnostics.
- Identify the alarm source by confirming whether the fault is displayed by the GA800 itself or by a connected encoder, servo, or option module, because E42 is not a standard GA800 power-drive fault code.
- Inspect the encoder connector by unplugging it and checking for bent pins, poor latch engagement, contamination, or damaged shells, then re-seat the connector firmly until it clicks.
- Verify encoder wiring and pinout by comparing the installed cable to the encoder and option manual, checking for swapped, open, or shorted conductors and confirming proper shield grounding.
- Check cable routing and grounding by separating the encoder cable from high-power wiring, welding cables, or other noise sources, and verifying that the cable shield is grounded only at one end per Yaskawa grounding recommendations.
- Reset the fault by pressing the RESET button on the keypad while the fault code is displayed, or cycle power if required by your GA800 manual procedure.
- Substitute the encoder or feedback option module if the alarm persists after connector and wiring checks, using a known-good spare to isolate whether the encoder, option card, or drive feedback input has failed.
Parts Often Needed
| Part | Notes |
|---|---|
| Encoder connector and mating cable assembly | Amazon | Match the connector shell and pin count to your encoder model and cable length to your machine. |
| Replacement encoder | Amazon | Must match the resolution, voltage, and mounting of the original encoder specified in your option manual. |
| Feedback option module or card | Amazon | If your GA800 uses a plug-in encoder interface card, order the exact Yaskawa option part number for your drive model. |
When to Call a Pro
Call a qualified Yaskawa technician or industrial controls specialist if you are not familiar with encoder feedback systems, if the alarm does not clear after re-seating the connector, or if you lack the tools to verify cable continuity and pinout. Encoder wiring errors can damage the drive’s feedback input circuitry, and incorrect grounding or noise mitigation can cause intermittent faults that are hard to trace. A professional can use an oscilloscope to verify encoder signal integrity, confirm proper grounding, and substitute known-good modules to isolate the failed component without risking further damage.
Rough cost: A pro service call runs about $200-600.