You're riding along and suddenly your display flashes "E10" or "E06" and the motor cuts out. The first thought is usually great, the motor's dead and this is going to be expensive.More often than not, it isn't. E-bike displays show error codes for two boring reasons: a loose connector, or a sensor that needs to be reseated. This guide walks through every code you'll see on a UART2 display, what it actually means, and the order to check things before you start ordering expensive parts.
Error Codes Reference Table
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Code
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What it means
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E06
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Battery undervoltage
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E07
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Motor fault
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E08
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Throttle fault
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E09
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Controller fault
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E10
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Communication reception error
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E11
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Communication sending error
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E06 — Battery Undervoltage
What it means: The display is reading a voltage that's too low for the system.
Common causes:
- The battery is genuinely low
- Voltage sag under load (the battery drops below threshold when you climb a hill or push high assist)
- Dirty or loose battery terminals
Do this:
- Charge the battery fully and test again.
- If E06 only appears on hills or high assist levels, the battery may be aging — the cells can't hold voltage under load anymore.
- Remove the battery, clean the terminals with a dry cloth, and reseat it firmly.
Stop riding if: the code comes back immediately even with a full charge. That points to a weak battery pack or BMS issue, not a charging problem.
E07 — Motor Fault
What it means: The controller isn't getting a clean signal from the motor's Hall sensors.
Common causes:
- The motor cable connector came loose (common after a wheel removal or a hard bump)
- Water or corrosion in the motor connector
- A damaged motor Hall sensor or winding
Do this:
- Power off the bike and remove the battery.
- Find the motor cable where it exits the hub and plugs into the controller. Reseat it firmly — you should feel it click.
- Inspect the pins for bending, corrosion, or oxidation.
- If you recently removed the rear wheel, double-check the connector is fully seated and aligned.
Stop riding if: you smell burning, the connector is hot, or the code returns immediately after reseating. That's a motor or controller problem, not a loose plug.
E08 — Throttle Fault
What it means: The controller thinks the throttle is engaged when it shouldn't be, or can't read the throttle at all.
Common causes:
- The throttle didn't return to its resting position before you turned the bike on
- The throttle connector is loose or wet
- The throttle itself is worn or damaged
- Your bike doesn't have a throttle at all (many e-MTBs are pedal-assist only)
Do this:
- Make sure the throttle snaps back to center before powering on.
- Reseat the throttle connector on the handlebar side. Check the cable for kinks or cuts near the grip.
- Pro tip: If your bike has no throttle fitted and the display still shows E08, enter the P-settings menu and set P10 to 0. This tells the display there's no throttle connected, and the code will clear.
E09 — Controller Fault
What it means: The controller has detected an internal problem and locked out the motor to protect itself.
Do this:
- Power cycle the system: turn off, remove the battery, wait 30 seconds, reinstall, and restart.
- If E09 returns immediately, the controller is almost certainly damaged and needs replacement.
There's no quick fix for E09. Unlike E06, E07, or E08, this isn't a connector issue — it's the controller reporting a hardware fault.
E10 — Communication Reception Error
What it means: The display isn't receiving data from the controller. This is the most common error people see, and it has a checklist of possible causes — work through them in order, from simplest to most expensive.
Do this, step by step:
- Check the display cable. Follow the cable from the display down to the controller. Look for breaks, pinched spots, or a plug that's come loose. Reseat it.
- Check the controller-to-display plug. Inspect the pins for bending or corrosion. Dry any wet connectors.
- Unplug the speed sensor and test. If E10 disappears, the speed sensor is faulty — replace it.
- Unplug the throttle and test. If E10 disappears, the throttle is faulty.
- Unplug the motor Hall cable and test. If E10 disappears, the motor or its Hall sensor is faulty.
- If none of the above works, the issue is a protocol mismatch. UART2 displays speak a specific language (UART No.2 protocol). If the controller is running a different protocol, the display and controller simply can't talk to each other. In that case, you need a controller that matches the display, or vice versa.
Important: Don't use adapter cables to force incompatible plugs together. Check which connector your bike actually uses → before you buy a replacement.
E11 — Communication Sending Error
What it means: The display is trying to send commands to the controller but the controller isn't receiving them.
Common causes:
- A damaged display (the send circuit has failed)
- A loose or damaged cable
- A controller that's stopped responding
Do this:
- Check the display cable and plug first — same as E10.
- If the cable is fine, the display itself may be reaching end of life. Communication circuits on LCD displays can fail after years of vibration and weather exposure.
- Try a known-good display on the same controller. If E11 disappears, the old display is the problem — it's time for a replacement.
If you've ruled out the cable and the display, the controller may need service.
When to Stop Riding Altogether
A few situations aren't worth troubleshooting on the roadside:
- Burning smell or hot connectors — shut the system down, don't restart.
- E09 that returns immediately — the controller has a real fault.
- Power cuts in and out randomly while riding — that's unpredictable and unsafe.
- E10 or E11 that comes back after every connector check — the display or controller needs professional diagnosis.
If Your Display Needs Replacing
If you've worked through the checklist and the display itself is the problem (especially for E11 or a persistent E10 that isn't a loose plug), you'll need a UART2 display that matches your controller's connector.
HAYTRIX LCD displays use UART No.2 protocol, support 24V–60V auto voltage, and come with your choice of connector (5-pin, 6-pin, SM5, SM6, SM7). Browse UART2 displays → or contact us if you're not sure which connector matches your controller.
Frequently Asked Questions
What's the most common e-bike display error code?
E10 (communication error) is the most frequent, usually caused by a loose display cable or a controller/display protocol mismatch. E06 (undervoltage) is also common, especially on older batteries.
Can I reset the error code by disconnecting the battery?
Power cycling (turn off, remove battery, wait 30 seconds, reconnect) clears temporary codes. But if the underlying issue — a loose plug or a failed sensor — isn't fixed, the code will come back.
Do error codes mean my motor is broken?
No. Most codes point to connectors, sensors, or the display itself. Only E07 after you've reseated everything points to a potential motor issue, and E09 points to the controller.
My bike has no throttle. Why does it show E08?
The display defaults to expecting a throttle. Enter P-settings and set P10 to 0 — that tells the display no throttle is fitted, and E08 will clear.
Got an error code not listed here, or not sure whether your display or controller is at fault? Contact HAYTRIX with a photo of your display and connector — we'll help you figure out whether you need a new display, a new controller, or just a reseated plug.
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