Comau C5G — DRIVE OFF on DRIVE ON & Alarm Codes

Comau · intermediate · 25 min

When a Comau C5G robot drops to DRIVE OFF the moment you try to power it up, the controller is reporting a motor/encoder problem. Learn to read the C5G message format, find the real first-cause alarm, reset the state and re-issue DRIVE ON.

ℹ️ On a C5G, a DRIVE OFF … error upon DRIVE ON means the drive chain refused to enable — almost always a motor or encoder issue (often a connection). Don't just keep hammering DRIVE ON: read the earlier alarm that caused it.

Read the C5G message format first

Comau C5G diagnostic messages follow a fixed format on the teach pendant:


xxxx.yyyyy-zz : Text
  • xxxx — the stored-event progressive number (the order it happened).
  • yyyyy — the error code itself.
  • zz — the seriousness level.

That structure matters because faults cascade: the message on top is often a consequence, and the real cause is an earlier event with a lower progressive number.

What 'DRIVE OFF upon DRIVE ON' means

A message like 10 - DRIVE OFF Arm <arm_num> error upon DRIVE ON appears when you try to enable the robot and the drives immediately drop out. On the C5G this points at the motors and/or encoders — frequently an encoder connection problem (a loose or damaged feedback cable, a connector not fully seated, a resolver/encoder fault).

Step-by-step recovery

  1. Read the whole event list, not just the top line. Note the xxxx.yyyyy-zz messages and find the lowest progressive number — that earliest event is usually the true cause.
  2. Look up the code. If you have WinC5G, the list of errors and possible solutions is normally available in the robot itself — match your yyyyy code to its description and remedy.
  3. Check the motor/encoder chain the code points to: feedback cables and connectors on the flagged arm, for damage or a loose connection; the motor and encoder for the reported fault.
  4. Reset the alarm state on the pendant once you've addressed the cause.
  5. Issue DRIVE ON again. If the drives now hold, recover and resume; if it drops out again with the same code, the encoder/motor fault is still present — don't keep retrying, diagnose the hardware.

Why it keeps happening

If DRIVE ON repeatedly fails on the same arm, treat it as a real feedback/drive fault rather than a nuisance alarm — an intermittent encoder cable, a failing encoder, or a drive (DSA) fault will reproduce exactly this symptom. Fix the hardware; resetting alone won't hold.

Never do this

Don't defeat or jumper the drive-enable / safety chain to force the robot to power up — a DRIVE OFF is the controller refusing to run motors it can't trust. Find the motor/encoder cause, then reset and DRIVE ON.

Key points

  • C5G messages read xxxx.yyyyy-zz : Text — progressive number, error code, seriousness; the real cause is often the earliest (lowest xxxx) event, not the top line.
  • 'DRIVE OFF Arm <n> error upon DRIVE ON' means the drives dropped out on enable — a motor and/or encoder issue, frequently an encoder connection problem.
  • With WinC5G the list of errors and possible solutions is available in the robot itself — match your yyyyy code to its remedy.
  • Recover by finding the first-cause alarm, checking the flagged arm's feedback cables/connectors, resetting the alarm state, then re-issuing DRIVE ON.
  • Repeated DRIVE OFF on the same arm is a real feedback/drive (DSA) fault — diagnose the hardware; never jumper the drive-enable or safety chain.

Codes and symptoms

DRIVE OFF … upon DRIVE ON — Drives drop out on enable
Motor and/or encoder problem on the named arm (often an encoder connection). Find the first-cause event, check the feedback chain, reset, then DRIVE ON.
xxxx.yyyyy-zz : Text — C5G message format
xxxx = stored-event progressive number, yyyyy = error code, zz = seriousness level. Look up yyyyy in WinC5G's error list in the robot for the remedy.