Hiboy S2, S2 Pro and KS4: throttle error on the display (E2, or E7 on the S2 Lite)

The scooter turns on but won't accelerate, and the display shows E2 (or E7 on an S2 Lite). Hiboy's troubleshooting guide lists E2 as a throttle error on the S2, S2 Pro, S2 MAX, S2R, S2R Plus, KS4, KS4 Pro and MAX Pro, and E7 as the throttle error on the S2 Lite. Its fix in both cases is a new throttle (Hiboy troubleshooting guide). The short answer: make sure the lever isn't stuck and no brake is held, then replace the throttle.

Most likely cause

The thumb throttle sends a signal to the controller through a small sensor. When that signal is missing or out of range, the controller flags it and refuses to drive. Hiboy's fix for E2 (E7 on the S2 Lite) is to replace the throttle (Hiboy troubleshooting guide). Hiboy's guide also says a horizontal bar on the display, instead of a number, means a throttle or electronic brake failure and calls for replacing both parts.

Other causes to rule out

• A brake held on: Hiboy's common problems guide says an active brake signal can block acceleration, so release both levers fully. A brake sensor fault shows as E1 on the S2 family (E3 on the S2 Lite), with a new electronic brake as Hiboy's fix.
• Kick-start mode: the same guide says to check whether kick-start is on, which means the motor only helps once you've pushed off. Your manual explains the setting.
• A sticking lever: Hiboy says the throttle should move smoothly and return to rest, and not to ride if it sticks.

How to confirm

1. Power off, then power on with your hands off both brake levers and the throttle. Read the code.
2. Press the throttle slowly. It should move smoothly and snap back by itself. If it sticks, don't ride.
3. Squeeze and release each brake lever a few times, checking that both return fully.
4. Kick off to a slow roll and try the throttle, in case kick-start is set.
5. Look at the throttle cable where it leaves the lever and where the handlebar folds, for a pinch or cut. Compare with check brake cutoff and throttle.
6. If E2 (or the bar) stays, the throttle is the next part to change.

Fix options

Replace the throttle (easy to moderate)

Hiboy sells a throttle for the S2, S2 Pro, KS4, KS4 Pro, S2 MAX, MAX Pro, S2R and S2R Plus, and its S2 series parts page lists a separate S2 Lite throttle. The throttle page links a three part video tutorial, and an owner review there describes the job as unplugging the old throttle and plugging in the new one. Power off first and route the new cable the same way as the old one so it doesn't pinch when you fold the stem. The part can't be returned, so confirm your model first, and contact Hiboy if you're under warranty.

Replace the electronic brake (easy to moderate)

Only if the code is E1, or the display shows the bar and a new throttle didn't clear it. Hiboy lists an electronic brake for the S2 and S2 Pro on its parts page.

Controller diagnosis (pro)

If a new throttle and brake sensor don't clear the code, a shop should check the wiring between the handlebar and the controller. Don't open the controller yourself.

Parts

• Throttle (Hiboy part for your model)
• Electronic brake (only for E1 or the display bar)

Videos

When to get a pro

Get help if the code returns after a new throttle, if the cable is damaged inside the stem, or if the throttle ever sticks open while riding. See throttle not working and when to call a pro.

Sources

• Hiboy troubleshooting guide, hiboy.com
• common problems guide, hiboy.com
• throttle for the S2, S2 Pro, KS4, KS4 Pro, S2 MAX, MAX Pro, S2R and S2R Plus, hiboy.com
• S2 series parts page, hiboy.com
• Hiboy Scooter S2/S2pro Throttle Replacement/Repair, youtube.com

Stuck after these checks? Find a shop near you.