Accurate fault identification is essential when troubleshooting an OTIS GOEC escalator. The Service Tool and Operation / Control Panel provide diagnostic information that helps maintenance technicians identify which safety circuit or mechanical monitoring device has been activated.
In this Part 3 guide, we cover fault categories 24–35, including governor overspeed detection, anti-reversal monitoring, broken-step detection, skirt safety switches, step-chain sprocket monitoring, comb plate switches, handrail entry monitoring, broken step chains, handrail breakage, and emergency stop buttons.
The original Service Tool display messages and fault identifiers are retained below for reference.
Important: This article is just for reference. Actual fault diagnosis and reset procedures should follow the applicable equipment manual and site safety requirements.
24. Governor Overspeed Detection
Service Tool Display
6 Group: 0163 Drv S27 GR3
30 Fault: 0134 OS S27
Operation / Control Panel: OTIS GR3 (6 Group); OTIS S27 (30 Fault)
Possible Cause
When the drive machine speed exceeds 120% of its rated speed, the connected centrifugal overspeed governor activates the overspeed safety switch. The ECB board receives the signal and stops the escalator.
Recommended Action
The original documentation specifies contacting the Guangzhou OTIS Quality Department (PIC) for this fault.
Because this fault involves overspeed protection, the escalator should remain out of service until the cause has been assessed and the safety function verified by qualified personnel.
25. Anti-Reversal Device Monitoring (via RSFF)
Service Tool Display
6 Group: 0164 Drv K66 GR3
30 Fault: 0135 NRD up K66
Operation / Control Panel: OTIS GR3 (6 Group); OTIS K66 (30 Fault)
Possible Causes
Incorrect time settings for timers K063–K067.
Malfunction of one or more of these time relays.
Recommended Actions
1. Inspect the wiring of the relevant time relays and correct wiring faults or incorrect connections.
2. Check the time relays and replace any defective units.
3. After correcting the fault, press the reset button on the ECB board as specified in the original procedure.
4. Verify the timer on-delay settings:
|
Timer |
On-delay time |
| K063 | 6 seconds |
| K064 | 3 seconds |
| K065 | 3 seconds |
| K066 | 3 seconds |
| K067 | 2 seconds |
Confirm the required settings against the applicable equipment documentation before changing parameters.
26. Broken Step Detection
Service Tool and Panel Displays
Upper landing – broken step
6 Group: 0165 Upp S10 GR4
30 Fault: 0136 Lock up S10
Operation / Control Panel: OTIS GR4 (6 Group); OTIS S10 (30 Fault)
Lower landing – broken step
30 Fault: 0154 Lock lo S20
Operation / Control Panel: OTIS GR5 (6 Group); OTIS S20 (30 Fault)
Possible Cause
When a step breaks, its deflected section can contact the detection rod beneath it. This activates the associated safety switch, and the ECB board stops the escalator.
Recommended Actions
Replace the broken step.
Adjust the clearance between the long adjustment bolt and the step.
Check and adjust the safety-switch mounting clearance.
Inspect the spring plate and its contact with the associated trip mechanism.
Press the ECB board reset button only after the mechanical fault has been corrected and the safety circuit has been verified.
27. Skirt Safety Monitoring
The skirt safety switches detect interference or contact between the steps and the escalator skirt.
Service Tool and Panel Displays
|
Location |
Service Tool – 6 Group |
Service Tool – 30 Fault |
Panel indication |
| Upper landing, right | 0166 Upp S4 GR4 | 0137 HSS ul&r S4 | OTIS S04 |
| Upper landing, left | 0167 Upp S3 GR4 | 0138 HSS ul&l S3 | OTIS S03 |
| Lower landing, right | Not separately listed | 0152 HSS l&r S18 | OTIS S18 |
| Lower landing, left | Not separately listed | 0153 HSS l&l S19 | OTIS S19 |
The corresponding panel group indications are OTIS GR4 for the upper landing and OTIS GR5 for the lower landing.
Possible Causes
Foreign objects trapped between a step and the skirt.
Contact between a step and the skirt.
A deformed or displaced skirt panel.
Recommended Actions
1. If a step contacts the skirt, inspect and adjust the step or step-chain guide as appropriate.
2. Remove foreign objects from the step-to-skirt clearance.
3. Inspect the skirt for deformation and restore its correct shape or replace it if necessary.
4. Verify that the safety switch operates correctly before returning the escalator to service.
28. Step-Chain Sprocket Monitoring
Service Tool and Panel Displays
Right side
6 Group: 0168 Upp S94 GR4
30 Fault: 0139 CRMS ri S94
Operation / Control Panel: OTIS GR4 (6 Group); OTIS S94 (30 Fault)
Left side
6 Group: 0169 Upp S95 GR4
30 Fault: 0140 CRMS le S95
Operation / Control Panel: OTIS GR4 (6 Group); OTIS S95 (30 Fault)
Possible Cause
A cracked or damaged step-chain sprocket roller can cause the step chain to drop from its normal position, activating the associated safety switch. The ECB board then stops the escalator.
Recommended Actions
Remove and replace the damaged sprocket roller or component as required.
Manually reset the step-chain sprocket safety switch after the fault has been corrected, following the applicable procedure.
Inspect the surrounding mechanism to ensure that the chain and monitoring device are correctly positioned.
29. Upper-Landing or Handwheel Stop-Switch Monitoring
Service Tool and Panel Displays
6 Group: 0170 Upp S73 GR4
30 Fault: 0141 Handwh.S73
Operation / Control Panel: OTIS GR4 (6 Group); OTIS Q04 (30 Fault)
Possible Cause
The drive machine cover has been lifted, withdrawing its locking pin and activating the associated switch.
Recommended Action
Close and correctly secure the drive machine cover. Verify the switch position and safety circuit before restarting the escalator.
30. Comb Plate Monitoring
Service Tool and Panel Displays
Upper landing, right side
6 Group: 0171 Upp S2 GR4
30 Fault: 0142 CMB up&r S2
Operation / Control Panel: OTIS GR4 (6 Group); OTIS S02 (30 Fault)
Upper landing, left side
6 Group: 0171 Upp S2 GR4
30 Fault: 0143 CMB up&l S1
Operation / Control Panel: OTIS GR4 (6 Group); OTIS S01 (30 Fault)
Lower landing, right side
30 Fault: 0148 CMB l&r S17
Operation / Control Panel: OTIS GR5 (6 Group); OTIS S17 (30 Fault)
Lower landing, left side
30 Fault: 0149 CMB l&r S16
Operation / Control Panel: OTIS GR5 (6 Group); OTIS S16 (30 Fault)
Possible Causes
Foreign objects trapped between the steps and comb plate.
Contact or collision between a step and the comb plate.
A damaged or displaced comb plate.
When the comb plate is pushed upward, its linkage activates the safety switch. The ECB board receives the signal and stops the escalator.
Recommended Actions
1. Inspect the steps and comb plate for interference.
2. Remove any trapped foreign objects.
3. Adjust the steps or comb plate as required.
4. Replace a damaged comb plate.
5. Verify the safety-switch operation before restoring service.
31. Handrail Entry-Box Monitoring
Service Tool and Panel Displays
|
Location |
Service Tool display |
Operation / Control Panel |
| Upper landing, right | 0144 HRE u&r S23 | OTIS GR2 / OTIS S23 |
| Upper landing, left | 0145 HRE u&l S24 | OTIS GR2 / OTIS S24 |
| Lower landing, right | 0146 HRE l&r S21 | OTIS GR2 / OTIS S21 |
| Lower landing, left | 0147 HRE l&l S22 | OTIS GR2 / OTIS S22 |
The Service Tool messages above are listed as 30 Fault indications in the source documentation.
Possible Cause
A foreign object becomes trapped between the handrail and the front guard plate of the handrail entry box. The object pushes the plate and activates the safety switch, causing the ECB board to stop the escalator.
Recommended Action
Remove the trapped object and inspect the entry-box guard plate and associated safety switch for damage or deformation. Confirm correct operation before returning the escalator to service.
32. Broken Step-Chain Detection
Service Tool and Panel Displays
Right step chain
Service Tool: 0150 BC right S14
Operation / Control Panel: OTIS GR5 (6 Group); OTIS S14 (30 Fault)
Left step chain
Service Tool: 0151 BC left S15
Operation / Control Panel: OTIS GR5 (6 Group); OTIS S15 (30 Fault)
Possible Causes
Excessive step-chain elongation or a broken chain.
Chain-tensioning frame movement that activates the safety switch.
A step colliding with the comb plate and pulling the tensioning frame forward.
Recommended Actions
1. Adjust or replace the affected step-chain link or links as required.
2. Follow the approved isolation and mechanical handling procedure before inspecting the chain and comb plate.
3. Check whether the tensioning-frame bearings are damaged.
4. Verify that the tensioning frame can return to its correct position.
5. Confirm the chain tension and associated safety-switch operation before restarting.
The original source mentions releasing the brake and manually turning the drive to relieve interference. This is a specialist operation and must only be performed under the applicable manufacturer procedure and site lockout requirements.
33. Handrail Breakage Detection
Service Tool and Panel Displays
Left handrail
Service Tool: 0155 HR br.l S45
Operation / Control Panel: OTIS GR5 (6 Group); OTIS S45 (30 Fault)
Right handrail
Service Tool: 0156 HR br.r S46
Operation / Control Panel: OTIS GR5 (6 Group); OTIS S46 (30 Fault)
Possible Cause
When the handrail breaks, its tension at the detection wheel drops sharply. The handrail-break safety switch loses its required pressure condition and activates, causing the ECB board to stop the escalator.
Recommended Action
Replace the damaged handrail. Inspect the detection wheel and associated safety switch, then verify correct operation before returning the escalator to service.
34. Lower-Landing Stop-Switch Monitoring
Service Tool and Panel Displays
Service Tool: 0158 Stop low Q3
Operation / Control Panel: OTIS GR5 (6 Group); OTIS Q03 (30 Fault)
Possible Cause
The stop switch in the lower-landing junction box has been pressed.
Recommended Action
Check why the stop switch was activated and reset it only when appropriate. Confirm that the surrounding area and equipment are safe before restoring operation.
35. Emergency Stop Button Monitoring
Service Tool and Panel Displays
Lower landing emergency stop
6 Group: 0175 S25 ,S26 GR1
30 Fault: 0159 ESB low S25
Operation / Control Panel: OTIS GR1 (6 Group); OTIS S25 (30 Fault)
Upper landing emergency stop
6 Group: 0175 S25 ,S26 GR1
30 Fault: 0160 ESB low S26
Operation / Control Panel: OTIS GR1 (6 Group); OTIS S26 (30 Fault)
Possible Cause
An emergency stop button at the upper or lower landing has been pressed.
Recommended Actions
Check the relevant emergency stop button and its associated wiring.
Identify and correct any wiring fault.
Confirm that the emergency stop circuit and button function correctly before resetting and returning the escalator to service.
For accurate diagnosis, always refer to the equipment-specific documentation and approved service procedures.
Post time: Oct-29-2026