E-Bike Troubleshooter
Work through an e-bike fault the way a mechanic does: the free checks first — battery charged and clicked home, both brake levers fully released, the spoke magnet within 10 to 20 mm of its sensor (Bafang’s spec), connectors dry and pushed together, a restart with your feet off the pedals — and the expensive parts last. Pick what the bike is doing and the troubleshooter gives you the checks in order, then the price of each fix.
No sign-up · works on your phoneUpdated 9 sources
Troubleshooter
What’s the bike doing?
Showing an error code? Look it up first — it points straight at the part.
Worked example
The throttle works, but pedaling gets no help
The motor clearly runs, so the question is what’s stopping pedal assist. Check 1: the assist level isn’t on 0. Check 2: neither brake lever is resting on the grip — a brake switch that reads “on” cuts pedal assist. Check 3: restart with your feet off the pedals, so a torque sensor can zero itself (Shimano’s first step for W013). Still nothing? A brake cut-off switch repair is $55, a cadence sensor $75, a torque sensor calibration $125 — checked in that order.
Reference
Where to start, by symptom
| The bike… | Check first | Then |
|---|---|---|
| Won't turn on | Battery charged; take it out and click it back in; contacts clean and dry | Display cable; restart; battery test |
| Turns on, no assist | Assist level not 0; brake levers fully released; speed reading not stuck at 0 | Spoke magnet 10–20 mm from sensor (Bafang); restart feet-off; look up any code |
| Cuts in and out | Battery doesn't rattle in its mount; connectors pushed home | Heat on long climbs; battery sag under load — a battery test |
| Less range | Tire pressure; wheels spin freely with no brake rub | Assist level, hills, weight, cold; then a battery test |
| Won't charge | Another outlet; charger cables home; charge port clean | Charger matches the battery's voltage; battery test |
| New noise | Grinding under power: stop riding. Clicks: pedals and cranks tight | Bottom bracket; hub or motor gears; loose battery or accessories |
| Brakes spongy or weak | A firm point before the lever reaches the grip (Riese & Müller); pads above 3 mm with backing (SRAM) | Bleed: DOT yearly, mineral oil every two years (SRAM); rotors |
| Skipping gears | Chain wear under Park Tool's limit | Cable tension; derailleur hanger after a fall |
| Flats | Nothing left in the tire; rim tape covering the spoke holes; pressure | Tubeless: sealant under 2–7 months old (Stan's) |
How to use it
In 4 steps
- 1Pick what the bike is doing. If the display shows a code, look it up first — it points straight at the part.
- 2Answer one or two questions.
- 3Work through the checks in order, and stop at the first one that finds something.
- 4Not a do-it-yourself fix? The price of each likely repair is listed — text a photo for a firm quote.
Why cheapest-first, and no odds
A lot of e-bike faults look the same from the saddle: no assist can be a brake switch, a slipped magnet, a wet connector or a failed controller. The parts don’t cost the same. Here, a connector rebuild is $45; a controller is $95 plus the part. Checking the cheap things first is how you avoid paying for the expensive one you didn’t need.
The troubleshooter doesn’t tell you what’s “80% likely”. There’s no honest data for numbers like that, so it gives you the order to check in instead, and every specific figure — the 10–20 mm magnet gap, the 3 mm pad limit, the bleed intervals — comes from the part maker’s own manual.
Near the beach, add corrosion to the list: Tern calls salt corrosion a coastal problem, and it shows up first on connectors, battery contacts and charge ports. The maintenance planner covers keeping it from starting.
FAQ
Troubleshooter: questions
Why won't my e-bike turn on?
Start with the battery: charge it fully, then take it out and click it back into its mount — Bosch's first step for several battery codes. Check the metal contacts are clean and dry, any key switch is on, and the display's cable is plugged in, then hold the power button to restart. If the battery shows no charge at all and won't take one, it needs a test.
Why is my e-bike not giving any assist?
Check the assist level isn't on 0, and that neither brake lever rests on the grip — a brake cut-off switch that reads "on" stops assist. If the speed reads 0 while you ride, the spoke magnet has probably moved: Bafang's spec is 10 to 20 mm from the sensor. Restart with your feet off the pedals so a torque sensor can zero itself, and look up any error code.
Why does my e-bike keep cutting out?
Over bumps, it's usually a connection: a battery rattling in its mount (Shimano's fix for its power-loss warning includes stopping the rattle) or a loose connector. On long climbs, it can be heat protection — Bafang's motor-temperature code clears once the motor cools. At full power as the battery empties, a worn battery sagging under load is the suspect.
Why won't my e-bike battery charge?
Try another outlet and check both charger cables are pushed home, then look at the charge port for dirt, bent pins or scorching. Make sure the charger's output matches the battery's voltage. A battery stored empty for weeks can fall too low for a charger to start and needs a test. If the pack is swollen, hot, hissing or smells, stop — don't charge it.
Why do my e-bike brakes feel spongy?
Air or old fluid in a hydraulic brake. Riese & Müller's check: you should feel a distinct pressure point, and the lever shouldn't reach the grip. SRAM bleeds DOT brakes at least once a year and mineral oil every two years. If a lever reaches the grip, don't ride until it's fixed — and find your brake's fluid before anyone tops it up.
Something not answered here? Just ask — I’d rather talk it through than have you guess.
Sources
Where these numbers come from
- [1]Bafang DP C244/C245 display user manual (July 2022) (opens in a new tab)Restart first; speed magnet 10–20 mm from the sensor; motor temperature code on long climbs.
- [2]Bosch Purion original operating instructions (2020) (opens in a new tab)Remove and reinsert the battery; a blank display means restart.
- [3]Shimano STEPS E7000 and SC-EM800 user manuals (opens in a new tab)Restart with your feet off the pedals; stop the battery rattling in its mount.
- [4]Riese & Müller owner's manual, North America (09/2019) (opens in a new tab)A distinct pressure point before the brake lever reaches the grip.
- [5]SRAM brake service guide and pad support article (opens in a new tab)Pads at 3 mm with backing plate; bleed DOT yearly, mineral every two years; bed in new pads; contaminated pads are replaced.
- [6]Shimano dealer's manual DM-TRBR001 (opens in a new tab)Pads at 0.5 mm; rotors at 1.5 mm.
- [7]Park Tool, “When to Replace a Worn Chain” (opens in a new tab)0.5% on 11-speed and up, 0.75% on 10-speed or fewer.
- [8]Stan's, Tubeless Guide (opens in a new tab)Top off sealant every 2–7 months.
- [9]Tern, “How to prevent salt corrosion on your bike” (opens in a new tab)Salt corrosion is worst on coasts.
Last reviewed . Spot something wrong? Text (949) 891-5278 and it gets fixed.
Related tools
- E-Bike Error Code LookupPick your system, type the code: what it means and the maker's first step. Bafang, Bosch, Shimano, Rad, KT, Segway.
- Repair or Replace?Is your e-bike (or its battery) worth fixing? A ranked verdict that shows its reasoning.
- E-Bike Battery DecoderVolts and amp-hours to watt-hours, cell count, charge level from voltage, charge time, and whether it can fly.
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