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The short answer
Litter-Robot does not publish numbered error codes like a car’s OBD-II system. What it gives you is a light-bar pattern plus a matching notification in the Whisker app: solid blue means ready, flashing blue means the waste drawer needs emptying, flashing yellow means the bonnet is off, and any red pattern means the unit is paused on a sensor, jam, motor, or scale fault.
This guide indexes the documented Litter-Robot 4, 5, and EVO patterns and separates five-minute fixes from failed-part codes.
Contents
- How Litter-Robot reports a problem
- Full light-bar code table
- Two-part combination codes
- The five faults that cause most support tickets
- The unit simply won’t cycle
- Litter-Robot 3: what is different
- When to stop troubleshooting and order a part
- Other brands: PETKIT and Petlibro
- Our Verdict
- How We Researched This
- Sources
How Litter-Robot reports a problem
Every current Litter-Robot has a five-button panel — Power, Cycle, Reset, Empty, Connect — plus an LED light bar along the bezel. The bar is the primary diagnostic surface; the button LEDs are secondary. White on Power or Cycle during a firmware update is normal, a red Power button means a hardware reset fired, and a blue flashing Power button means the unit lost power.
Two things make the bar hard to read. Some faults are patterns, not colors: a yellow light traveling back and forth is "ping-pong," which differs from a yellow bar blinking in place. And the bar reports a symptom, not a diagnosis — a flashing yellow bar means the bonnet is off, whatever the reason.
Prerequisites, per Whisker: plugged in and powered on; connected and online in the app; firmware current. A surprising share of "error code" searches end at a firmware update.
Full light-bar code table
The table below consolidates the light patterns Whisker documents for Litter-Robot 4 — the generation whose full public light-code table is published. Litter-Robot 5 and 5 Pro use the same control-panel vocabulary and cross-reference the same articles. Patterns unique to the Litter-Robot 5 LCD screen or WasteID system are not published in that single table.
| Light-bar pattern | What Whisker says it means | Documented first fix |
|---|---|---|
| Blue, solid | Ready / idle at Home | No action |
| Blue, flashing | Waste drawer reported full | Empty drawer, press Reset, then Cycle |
| Blue + two yellow flashing | Scale triggered for more than 30 minutes ("excess weight") | Remove excess weight, move unit off carpet/mat/cord/grout line, press Reset |
| Blue + one yellow flashing near Connect | Onboarding mode, waiting to pair | Finish onboarding in the app |
| Blue + blue flashing at Connect | Connecting to Wi-Fi, or reconnecting after a drop | Wait; if it never connects, power cycle |
| Blue + solid white at Connect | Wi-Fi is turned off | Short press Connect |
| Blue + purple alternating | LitterHopper motor error (accessory) | Check LitterHopper seating and run a cycle |
| Blue + white alternating | Motor connection problem; globe rotation affected | Check motor connection; may need service |
| Red, solid | Cat sensor triggered — a cat is in the globe | Wait for the cycle delay, or press Reset |
| Red, flashing | Weight or motion detected for over 30 minutes | Reset to zero the scale; clean the curtain sensors |
| Red, momentary flash on any button press | Control Panel Lockout Mode is active | Unlock via the app or button combination |
| Red + two white flashing | Globe position cannot be detected | Cycle and re-home the globe |
| Red + two yellow flashing | Globe jammed or overloaded; motor stopped | Remove excess litter/weight, clear the obstruction |
| Red + green alternating | Unit lost factory scale calibration values | Base replacement required — contact support |
| Red + blue alternating | The three laser "curtain sensors" need cleaning | Clean the laser sensors in the bezel |
| Red ping-pong (one red light traveling) | Motion detected in the waste drawer | Check for a cat, pet, or debris in the drawer area |
| Purple, solid | Sleep Mode active | Long press Cycle to toggle |
| Yellow, solid | Unit paused | Press Cycle or Reset; power cycle if it does not resume |
| Yellow, flashing | Bonnet removed | Refit bonnet; unit resumes about five seconds later |
| Yellow ping-pong | Anti-pinch sensor activated | Check the waste chute and pinch bars |
| Yellow round-robin | Normal — a Clean or Empty cycle is running | No action |
| Green, 1–5 solid | Cycle delay setting being edited | Hold Empty for 3 seconds to save and exit |
| Green, flashing | Manual cycle completed successfully | No action |
| Green round-robin | Normal operation | No action |
| Green + white alternating | Anti-pinch fault detected during power-up | Inspect pinch bars; may need service |
| Green ping-pong | Curtain sensors auto-calibrating | No action |
| Green + partial red flashing | Auto-calibration failed; sensors need cleaning | Clean the curtain sensors |
| White Power button | Firmware update in progress | No action |
| White flashing Power button | Firmware update complete | No action |
Two notes. "Curtain sensors" is Whisker’s name for the three laser sensors in the top of the bezel that measure drawer level. "Ping-pong" is Whisker’s own term for a single lit LED moving back and forth, and it is not always a fault — green ping-pong is normal calibration.
Two-part combination codes
Litter-Robot 4 has a second code language: three solid lights plus two flashing lights of different colors. These are the least understood patterns and the ones most likely to be a real hardware fault.
| Combination | Documented cause | Documented solution |
|---|---|---|
| Red / Green (3 solid / 2 flashing) | Low system voltage | Replace the power supply |
| Blue / Green (3 solid / 2 flashing) | Problem with a USB device | Power off, wait 5 seconds, power on, unplug the USB device |
| Blue / Yellow (3 solid / 2 flashing) | Robot or scale feet are unbalanced | Level the unit; keep it off carpet, mats, cords, grout lines, and walls |
| Yellow / Red (3 solid / 2 flashing) | Dirty laser 2, or laser-board firmware does not support the feature | Follow the flashing-red steps; update firmware via the app |
| Yellow / Green and Yellow / Blue (3 solid / 2 flashing) | User-initiated 4×4 calibration mode | No action |
| White / Blue (3 solid / 2 flashing) | Power supply is defective | Replace the power supply |
| Green / Purple alternating | Hall-effect board disconnected | Replace the base |
| Blue / White alternating | Motor disconnected | Check the motor connection; contact support |
| Yellow / Purple alternating | Scale Calibrate or Audit mode | Power off, wait 5 seconds, power on |
| Blue with white flashing Wi-Fi button | Wi-Fi chip is defective | Replace the base |
| Blue with red flashing Wi-Fi button | Cannot connect to the router | Verify the router is up; power cycle the robot |
The pattern to notice: power supply and base appear over and over as the documented fix. If you see a three-plus-two pattern, you are usually past the "clean this and try again" stage.
Under WhiskerCare warranty, replacement parts are free through your account under "My Robots." After warranty, they are sold individually — see what Litter-Robot ownership actually costs over five years.
The five faults that cause most support tickets
Whisker has written dedicated step-by-step articles for these five — a reasonable proxy for which faults generate the most owner contact.
1. Flashing blue: the drawer-full indicator is lying
A flashing blue bar means the Drawer Full Indicator thinks the drawer is full. On Litter-Robot 4 the DFI uses three laser curtain sensors, and it is easy to fool. Documented causes, in Whisker’s order:
- The liner is stretched or not pressed flat. White bags work best; dark bags can read inaccurately, especially when the drawer is empty.
- Debris on the bezel. Wipe with a dry cloth and vacuum the perimeter with a brush attachment.
- Outdated firmware.
- Cat fur in the globe’s seal strips, crossing the sensor’s view when the globe rotates.
- Obstruction at the waste port.
- A failed DFI calibration. If calibration fails, the panel shows a yellow bar with a red flashing light for five seconds, then cycles Home.
If none of that clears it, Whisker’s documented repair is a laser board or a base.
Before you panic: when the unit detects a full drawer it cycles two more times before it stops cycling automatically. A box that empties fine on a manual Cycle but refuses to self-cycle is not a broken sensor.
After any change to the drawer — new liner, emptying, adding litter, moving the unit — press Reset, so the sensors re-zero.
2. Flashing red: the scale thinks a cat is still inside
A flashing red bar means the cat sensor has been triggered for more than 30 minutes — almost always the weight scale detecting weight that isn’t a cat.
Documented first moves:
- Check the litter level. If litter is above the raised MAX fill line, remove some until it sits just below.
- From Home, press Reset twice to zero the scale — the bar flashes white when it takes.
- If the unit is stuck mid-cycle, long press Reset for 3 seconds to zero the scale; the cycle should then complete.
If that does not work, the next documented steps are cleaning the three curtain sensors, then removing the bonnet and globe to inspect the seal strips and waste port, then updating firmware. The unrecovered outcome is again a laser board or base replacement. Placement drives this fault more than most owners expect: carpet, a litter mat partly under the unit, a power cord under a foot, a tile grout line, or any side touching a wall can all hold the scale in a false "occupied" state.
3. Red with flashing yellow: the globe is jammed or overloaded
This is the overtorque fault. The unit monitors motor current, so if the globe slows under resistance, this pattern appears. Whisker notes the unit retracts and retries; after three failed restarts it tries to return Home, and if interrupted three more times it stops wherever it is stuck. Cheap things to rule out first:
- Overfilled litter. If you just topped up, the extra weight can slow the globe enough to trigger the fault; if it clears on the next cycle, there is no fault.
- A swollen or oversized clump in the globe.
- Globe damage — deep scratches, separating seams, cracked plastic, or a loose gear track.
- Seal strips peeling up or packed with fur, which drags against the rotation.
- The carbon filter cover not fully seated. Whisker explicitly calls this out: if the cover is not flush and snapped in, it can interrupt the cycle.
- Motor or gear problems in the base.
The fix ladder runs from removing excess litter, to removing the fence, shield, or LitterHopper, to pulling the globe and running the motor test, to ordering a globe, seal strips, motor, or base.
4. Yellow ping-pong: anti-pinch sensor triggered
Two anti-pinch sensors sit at the sides of the waste chute and monitor continuously. If one trips, the globe stops and retracts for five seconds, pauses two, and retries; after three attempts it holds position until you power off and on.
Documented checks: look inside the waste drawer for foreign objects; clean both pinch bars; press inward on each pinch bar and confirm an audible click; seat the carbon filter cover; clear the waste port and globe track. If the fault survives, the documented part is a base replacement.
5. Blue and white alternating: motor fault
This means the motor connection is the problem. Whisker’s guidance is to check the motor connection and contact customer support; a motor installation guide is published, but this is where most owners let the warranty do the work.
The unit simply won’t cycle
Whisker’s FAQ answers "why is my Litter-Robot not cycling" with the same list the light codes imply:
- Waste drawer is full (flashing blue).
- Sleep Mode is enabled (solid purple).
- Excess weight detected (blue plus flashing yellow).
- Litter level is too high.
- The cat sensor is dirty or malfunctioning.
- The unit is not on a level surface, or is placed incorrectly.
- A mechanical issue with the motor or gear mechanism.
Items 1 through 6 are free to fix; item 7 is not. Work the free list twice before assuming a part.
One limit worth noting: the pattern reports a symptom, not a part. Red with flashing yellow says the globe met resistance — not whether the cause was a clump, a warped globe, a seal strip, or a failing motor. The app names the fault in words, so if the two disagree, trust the app text and the article it links to.
Litter-Robot 3: what is different
Litter-Robot 3 and 3 Connect use a different control panel — glider buttons and a three-LED status display — and the light meanings do not map one-to-one onto Litter-Robot 4’s.
[DATA NOT VERIFIED: we could not retrieve Whisker’s Litter-Robot 3 light-code article. The URL pattern used for the Litter-Robot 4 light-code guide returns 404 for the LR3 equivalent, and the official LR3 light and button table lives in the manual PDF, which we could not extract text from. Do not rely on any Litter-Robot 3 light table that is not sourced from Whisker’s own manual.]
What we can confirm: LR3 and LR3 Connect were discontinued in the U.S. as Whisker moved to EVO, 5, and 5 Pro, and Whisker says it will keep supporting LR3 owners with parts, warranty service, and tech support. One difference affects how you read a code: minimum safe cat weight. On Litter-Robot 5, 4, and EVO, kittens can use automatic mode from 3 pounds; on LR3 the documented minimum is 5 pounds. A lighter kitten can trip the cat sensor without triggering a normal cycle, and Whisker’s workaround is to leave the unit off and cycle it manually.
When to stop troubleshooting and order a part
The cutoff rule: if a code’s documented solution says "clean, reset, level, or update firmware," keep going. If it says replace the power supply, base, laser board, or motor, start the parts process.
Three practical points:
- Check warranty first. WhiskerCare gives you the replacement part at no cost. Ordering before checking is the most common avoidable cost.
- Firmware is not a formality. Several combination codes are documented as "laser board firmware does not support this feature," with the app update as the fix.
- The unit is repairable, not disposable. Power supplies, bases, laser boards, motors, globes, bezels, seal strips, and filters are all sold separately — a big part of the picture in the five-year Litter-Robot cost model.
Other brands: PETKIT and Petlibro
There is no cross-brand equivalent list, because each brand exposes faults differently.
[DATA NOT VERIFIED: neither PETKIT nor Petlibro publishes a consolidated public error-code table we could retrieve. PETKIT surfaces faults as app alerts and on-device indicators on its Purobot line; Petlibro documents Luma behavior such as "if a cat is detected, Luma pauses instantly" and app alerts for low litter level, lens obstruction, and inactivity for 24 hours.]
The principles carry over: check for a full waste bin, remove excess weight, confirm a hard level surface, and clear debris from sensors. For which machines have which sensors, see how the Litter-Robot 5, 4, and EVO differ and our best automatic litter box roundup.
Our Verdict
If you only do one thing: press Reset, then Cycle, from the Home position — after confirming the litter is below the MAX line, the unit sits on a hard level surface, and nothing touches the sides. That resolves the two most common patterns (flashing red and blue-with-flashing-yellow), because both are scale faults.
If you are choosing a machine for the easiest failure recovery: Litter-Robot — not because it fails less, but because Whisker publishes a full light-code table, a troubleshooting article per pattern, and individual parts for every subsystem, and because the waste drawer takes any bag that fits. Other brands have not matched that in the public documentation we checked; our roundup of automatic litter boxes covers the alternatives.
If your unit keeps faulting, suspect the litter before the hardware — the wrong litter is a documented cause of overtorque jams and false drawer-full readings, and changing it costs nothing. See best litter for automatic litter boxes.
For parts and consumable pricing before you commit, see automatic litter box consumables cost.
If you need the replacement part: buy the Litter-Robot 4 power supply from Whisker’s own store rather than a third-party listing, so the voltage and plug match the unit you have.
How We Researched This
- We read Whisker’s own support articles, not third-party copies, and built the light-code table from the published Litter-Robot 4 light codes guide plus the per-fault articles for drawer-full, cat-sensor, overtorque, and anti-pinch faults.
- We treated every documented step as part of an ordered ladder and preserved that order, because the sequence is the product: quick checks first, teardown second, firmware third, parts last.
- We cross-checked individual claims against a second official source where one existed, including the Australian distributor’s support knowledge base for Litter-Robot 4 light codes.
- We did not test any unit, and we did not survey owners. Where a code’s cause is not published, we say so rather than guess.
- We flagged the Litter-Robot 3 section as unverified rather than reuse a light table we could not source from Whisker.
Read more about our standards at /how-we-research/.
Sources
- https://www.litter-robot.com/support/article/litter-robot-4-light-codes-guide/
- https://www.litter-robot.com/support/article/litter-robot-4-drawer-full-indicator-dfi-sensors/
- https://www.litter-robot.com/support/article/litter-robot-4-flashing-red-cat-sensor-fault/
- https://www.litter-robot.com/support/article/litter-robot-4-red-with-partial-yellow-flashing-over-torque-fault/
- https://www.litter-robot.com/support/article/litter-robot-4-yellow-ping-pong-pinch-detect/
- https://www.litter-robot.com/support/article/litter-robot-4-blue-yellow-flashing-excess-weight-detected/
- https://www.litter-robot.com/support/article/how-much-litter-do-i-put-in-litter-robot/
- https://www.litter-robot.com/support/article/litter-robot-4-manual/
- https://www.litter-robot.com/support/article/litter-robot-5-manual/
- https://www.litter-robot.com/support/article/litter-robot-3-manual/
- https://www.litter-robot.com/support/litter-robot-4/
- https://www.litter-robot.com/support/litter-robot-5/
- https://www.litter-robot.com/support/litter-robot-3/
- https://www.litter-robot.com/faq.html
- https://www.litter-robot.com/litter-robot-4-power-supply.html
- https://www.whisker.com/litter-robot-comparison-chart
- https://catevolution.freshdesk.com/support/solutions/articles/51000381510-litter-robot-4-light-codes
- https://www.petkit.com/products/purobot-ultra
- https://petlibro.com/products/luma-smart-litter-box.json