FANUC Alarm SRVO-068 — SERVO DTERR alarm
Error- Hardware
- Pulsecoder (encoder)
- Controllers
- R-J3iB / R-30iA / R-30iB
- FANUC class
- SERVO2
- Hardware family
- FANUC Pulsecoder, backup battery and position loss alarms
Manufacturer wording — SERVO DTERR alarm (Grp:%d Ax:%d)
The manual prints placeholders; your controller fills them in with the real group, axis or number.
FANUC SRVO-068 (“SERVO DTERR alarm”): A request signal was sent to the serial pulse coder, but no serial data was returned. First check: 1. Check the shielding for the pulse coder cables to ground. Likely part: Pulsecoder (Pulsecoder (motor encoder)).
Updated 2026-10-22 · LogrobotLM reference
Description
A request signal was sent to the serial pulse coder, but no serial data was returned.
Remedy
1. Check the shielding for the pulse coder cables to ground. The ground wire is the yellow and green wire connected to the robot base. 2. Inspect the pulse coder cable set for breaks, internal robot set, and P1 cable running from the robot to the controller. WARNING: By completing the next step you will be altering the positional reference for the robot since you are replacing hardware. You must slowly verify all positional data and touch-up any paths or points that have changed. Otherwise, you could injure personnel or damage equipment. 3. Replace the pulse coder and remaster the robot. 4. Replace the P1 cable. 5. Replace the internal cable set.
Field diagnosis
The Pulsecoder returns no serial data in response to the amplifier request.
What to check
- Check the seating of the robot connection cable at the amplifier end (CRF8 on R-30iB) and at the motor end, and the shield grounding in the cabinet; then replace, in order, the robot connection cable, the robot internal cable, the Pulsecoder, the amplifier.
- Note: DTERR/CRCERR/STBERR trio = link, not encoder; do not change the motor first.
- Diagnostic sequence “Battery box / motor”: BZAL that returns after the batteries have been replaced: the message says "batteries", but the cause is not the battery. Discriminating test 1: battery box contact springs (sagged → no more contact despite good batteries). Discriminating test 2: swap the encoder cables of two axes and reset; if the fault follows the cable, it is the cable; if it stays on the axis, it is the encoder/motor.
- Diagnostic sequence “Encoder link, not the encoder”: The three codes 068/069/070 appear together, sometimes with PHAL (064) or CSAL (066): the encoder serial link is at fault, and the encoder codes accompanying them are symptoms. Robot connection cable connectors at both ends, shield grounding, robot connection cable, robot internal cable; encoder and amplifier only after that. Do not replace the motor first.
Part to check / replace
FANUC SRVO-068 points to the hardware below — start here before ordering.
Tap a part for every code that points to it — and verify the exact variant for your controller before ordering.
Related codes
Same hardware involved
Indicative field information — the robot manufacturer's manual and safety procedures always prevail. Never bypass a safety device; apply lockout/tagout (LOTO) before any physical intervention. How this reference is built →