Every page in this library follows the same structure: what the alarm means → the most common causes (ranked by field frequency) → a step-by-step check sequence → when to stop and call an engineer. Codes are grouped by fault family below.
Battery & Mastering (5)
| Code | Alarm | What it means |
|---|
| SRVO-062 | BZAL Alarm (Group / Axis) | The absolute position data of the pulse coder was lost. The robot no longer knows where its axes are, so it… |
| SRVO-065 | BLAL Alarm - Battery Voltage Low | The backup battery voltage for the pulse coders has dropped below the warning level. Position data is still… |
| SRVO-075 | Pulse Position Mismatch | The pulse coder position changed while the controller was powered off, so the stored position no longer… |
| SRVO-027 | Robot Not Mastered | The robot has no valid mastering data. This typically follows BZAL alarms, board replacement, or loading a… |
| SRVO-038 | Pulse Mismatch (Group / Axis) | The controller detected a pulse count mismatch for the axis between power cycles - the feedback position… |
Servo & Drive (9)
| Code | Alarm | What it means |
|---|
| SRVO-021 | SRDY Off (Group / Axis) | The servo amplifier for the specified axis did not report ready when servo power was switched on, so the… |
| SRVO-023 | Stop Error Excess (Group / Axis) | While the axis was supposed to hold position, the position error exceeded the limit - the axis drifted or was… |
| SRVO-024 | Move Error Excess (Group / Axis) | During motion the following error exceeded the limit - the axis could not keep up with the commanded… |
| SRVO-043 | DCAL Alarm - Discharge Alarm | Regenerative energy from decelerating axes exceeded what the discharge circuit could absorb. The DC link… |
| SRVO-044 | HVAL Alarm - High Voltage | The DC link voltage inside the amplifier exceeded the upper… |
| SRVO-045 | HCAL Alarm - High Current | Abnormally high instantaneous current flowed from the amplifier to the motor, usually indicating a short… |
| SRVO-046 | OVC Alarm - Overcurrent (Average) | The average current over a period exceeded the rating - the axis has been working too hard for too… |
| SRVO-047 | LVAL Alarm - Low Voltage | The control power supply voltage inside the amplifier dropped below the lower… |
| SRVO-050 | CLALM - Collision Detect Alarm | The collision detection function judged that the robot hit something. Servo power is cut immediately to limit… |
Amplifier & Hardware (18)
| Code | Alarm | What it means |
|---|
| SRVO-057 | FSSB Disconnect | The FSSB optical fiber link between the main board (axis control card) and the servo amplifiers was… |
| SRVO-068 | DTERR - Data Transmission Error | Serial data communication between the servo amplifier and the pulse coder failed or is severely… |
| SRVO-069 | CRCERR - CRC Error | Data from the pulse coder fails CRC checksum validation - the signal is being corrupted in… |
| SRVO-071 | SPHAL - Soft Phase Alarm | The detected current speed of the motor is abnormally high - feedback data does not match reality, usually a… |
| SRVO-072 | PMAL - Pulse Coder Phase Alarm | The pulse coder detected an internal phase error - an internal encoder… |
| SRVO-073 | CMAL - Pulse Coder Count Error | The pulse coder's internal counter detected an error - position feedback from this encoder is… |
| SRVO-074 | LDAL - Pulse Coder LED Alarm | The LED inside the optical pulse coder has degraded below usable level. The encoder will fail completely… |
| SRVO-135 | FSAL - Fan Stop Alarm | A cooling fan inside the servo amplifier has stopped or is running below… |
| SRVO-136 | DCLVAL Alarm (Group / Axis) | The amplifier hardware detected an abnormal current condition. In field practice this points strongly to a… |
| SRVO-156 | IPMAL - IPM Alarm | The Intelligent Power Module (IPM) in the servo amplifier triggered its internal protection - overcurrent,… |
| SRVO-157 | CHARGE Alarm | The DC link charge circuit in the amplifier failed to charge the bus capacitors within the expected time at… |
| SRVO-213 | Fuse Blown (Panel PCB) | A fuse on the panel PCB has blown, indicating an overcurrent on that… |
| SRVO-216 | OVC (Total Current) | The combined current of all axes exceeded the amplifier's total… |
| SRVO-221 | Lack of DSP (Axis) | The controller does not detect the DSP (servo control) for the specified axis - the axis control card is… |
| SRVO-251 | DB Relay Abnormal | The dynamic brake relay inside the servo amplifier did not switch as… |
| SRVO-252 | Current Detect Abnormal | The current feedback detection circuit in the amplifier reads outside the plausible… |
| SRVO-253 | Amplifier Overheat | The servo amplifier heatsink temperature exceeded the… |
| SRVO-291 | IPM Overheat | The temperature inside the intelligent power module exceeded its limit - the power stage itself is running… |
Safety Chain & E-Stop (16)
| Code | Alarm | What it means |
|---|
| SRVO-105 | Door Open or E.Stop | A safety fence door was opened or an emergency stop was activated while the system was in automatic… |
| SRVO-201 | Panel E-Stop | The emergency stop button on the operator panel is pressed, or its circuit is… |
| SRVO-202 | TP E-Stop | The emergency stop button on the teach pendant is pressed or its circuit is… |
| SRVO-204 | External E-Stop (SVEMG Abnormal) | The external emergency stop input is active, or the two channels of the external E-stop circuit… |
| SRVO-230 | Chain 1 (+24V) Abnormal | The +24V side of the dual-channel emergency stop chain circuit is abnormal. The two safety channels no longer… |
| SRVO-231 | Chain 2 (0V) Abnormal | The 0V side of the dual-channel emergency stop chain is abnormal. Same family as SRVO-230, opposite… |
| SRVO-232 | NTED Input Abnormal | The NTED (external enabling device) input is in an abnormal state - the external enable signal chain… |
| SRVO-235 | Short-Term Chain Abnormal | A momentary mismatch was detected in the E-stop chain - the fault appeared and disappeared within a short… |
| SRVO-271 | EXEMG1 Status Abnormal | The external emergency stop line status is inconsistent between the two safety… |
| SRVO-277 | Panel E-Stop (SVEMG Abnormal) | The operator panel E-stop circuit shows a mismatch between its two… |
| SRVO-280 | SVOFF Input | The SVOFF (servo off) input signal is active - an external device is requesting servo power… |
| SRVO-348 | DCS MCC OFF Alarm | The Dual Check Safety (DCS) system detected that the main contactor (MCC) opened abnormally or its feedback… |
| SRVO-004 | Fence Open (Legacy RJ3) | The safety fence circuit is open. Common on older RJ3-era controllers still running in used… |
| SRVO-005 | Robot Overtravel | An axis hit its overtravel limit switch - the hardware stop beyond the software… |
| SRVO-006 | Hand Broken (HBK) | The hand breakage detection signal (HBK) activated - the system believes the gripper/hand is damaged or its… |
| SRVO-007 | External Emergency Stop (Legacy) | The external emergency stop circuit is open on legacy… |
Communication (1)
| Code | Alarm | What it means |
|---|
| SYST-067 | Panel HSSB Disconnect | High-speed serial communication between the controller and the teach pendant was… |
Motion & Path (4)
| Code | Alarm | What it means |
|---|
| MOTN-017 | Limit Error (Group / Axis) | The commanded position is beyond the software stroke limit of the… |
| MOTN-018 | Position Not Reachable | The target position cannot be reached with the current robot configuration - outside the workspace or an… |
| MOTN-023 | In Singularity | A linear/circular move passed through a wrist singularity (J5 axis near 0 degrees), where infinite joint… |
| MOTN-056 | Speed Limits Used | The programmed speed was clamped by a system speed limit (for example T1 mode limits). Mostly informational,… |
Using this library on a running robot? Write down the full alarm text and what the robot was doing when it fired. If two alarms appear, the first one in the list is usually the root cause. And remember: never short out safety circuit contacts — if an alarm comes back after two reset attempts, the underlying fault is still there.
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This library is written by the Henghuan Robotics repair team from field service experience, as a troubleshooting reference. Alarm behaviour can vary by controller version. Henghuan is an independent service provider, not affiliated with or endorsed by FANUC.
