Carrera and Raleigh E-Bike Torque Sensor Problems & Fix Guide
Fix Carrera E21 & E22 Errors – SR Suntour Torque Sensor Guide
If your Carrera or Raleigh e-bike display shows an E21 or E22 error code, loses pedal assist, or cuts out while riding, the SR Suntour HESC torque sensor is one of the first parts to check.
This guide explains how to identify the fault, understand what’s happening, and choose the correct replacement sensor.
Quick Answer
- E21 = torque sensor electrical fault
- E22 = torque sensor mechanical fault
- No pedal assist or cutting out = commonly linked to the torque sensor
Next step: confirm the fault before replacing any parts.
How to Confirm a Faulty Torque Sensor
- Turn the bike on and enable pedal assist
- Start pedalling
- If the motor does not respond, the sensor may not be detecting force
- If E21 or E22 appears, the system has already identified a sensor-related issue
- Check the connector at the torque sensor for dirt, corrosion, or a loose fit before replacing the sensor
Common Symptoms of a Faulty Torque Sensor
- The motor does not respond to pedalling despite the bike powering on
- Assistance feels inconsistent or delayed
- Power drops under load, such as when climbing
- Unusual resistance through the pedals
- Intermittent performance that worsens over time
Typical Torque Sensor Faults on Carrera & Raleigh E-Bikes
Most pedal-assist faults on Carrera and Raleigh e-bikes using the SR Suntour HESC system are caused by the torque sensor.
This often shows up as a complete loss of assistance, inconsistent motor response, or the bike cutting out while pedalling. In many cases, these problems appear alongside E21 or E22, which point to an electrical or mechanical fault within the torque sensor assembly.
If your bike is showing these symptoms, replacing the torque sensor is often the fix that restores normal pedal assist.
What Is the SR Suntour HESC Torque Sensor?
The SR Suntour HESC (Human Electro Synergy Components) system uses an Active Torque Sensor (ATS) located at the crankset. It measures how much force you apply to the pedals and adjusts motor assistance accordingly.
Inside the unit, two castellated ridges sit side by side: one fixed to the crank arm and the other to the chainwheel, with springs between them. As pedal pressure is applied, the movement between these parts is read electronically to control motor output.
Over time — especially in wet or salty conditions — the seal can degrade, allowing dirt into the mechanism. This leads to wear and eventual failure of the internal components.
Which Bikes Use This System?
The SR Suntour HESC system is fitted to a range of Carrera and Raleigh e-bikes, including:
- Carrera: Crossfire-e, Vulcan-e, Vengeance E, Subway E
- Raleigh: models using the same HESC drivetrain
Important: compatibility is determined by connector type and year of manufacture, not by model name alone.
SR Suntour HESC Error Codes Explained
| Error Code | Error Description | Recommended Action |
|---|---|---|
| E21 | Torque sensor electrical fault | Inspect connections and the sensor. Replace the torque sensor if the fault persists. |
| E22 | Torque sensor mechanical fault | Inspect the torque sensor and replace it if it is worn, damaged, or still faulty after checks. |
When to Replace the Torque Sensor
Replace the torque sensor if any of the following still apply after checking the connector and basic connections:
- E21 error remains on the display
- E22 error remains on the display
- The bike powers on but there is still no pedal assist
- The bike keeps cutting out or losing power under load
- The sensor shows signs of wear, contamination, or damage
In most cases, replacing the torque sensor is more reliable than attempting to repair it. The unit is sealed, and internal service parts are not normally available separately.
How to Replace the Torque Sensor
The sensor is located behind the crank assembly at the chainwheel and can be accessed by removing the crank assembly.
Take care: small shim washers may be present inside the assembly and should not be lost. These must be retained and refitted correctly during installation of the new sensor.
- Remove the crank assembly using a crank extractor
- Note the position of any shim washers before removing the sensor
- Disconnect the existing torque sensor
- Fit the correct replacement sensor and refit any washers in the same order
- Reconnect the sensor securely
- Refit the crank assembly
- Once fitted, test pedal assist across all modes before riding
4-Pin vs 6-Pin Torque Sensors
- 4-Pin: generally pre-2021 bikes
- 6-Pin: generally 2021 onwards
- Not interchangeable
If your checks confirm a torque sensor fault, you can browse the correct SR Suntour HESC torque sensors here.
View the 4-pin torque sensor replacement — £39.99
View the 6-pin torque sensor replacement — £44.99
Important: Check Before Ordering
4-pin and 6-pin torque sensors are NOT interchangeable.
Ordering the wrong version will not work with your bike. If unsure, check your connector or contact us before ordering.
Frequently Asked Questions
Can I repair the torque sensor instead of replacing it?
In most cases, replacement is the most reliable solution. The SR Suntour HESC torque sensor is a sealed unit and its internal components are not usually available separately. Once contamination or wear has affected the mechanism, replacing the sensor is normally the most practical fix.
Why does my e-bike keep cutting out?
This is often linked to a failing torque sensor or a loose connection. If the bike cuts out under load or delivers inconsistent assistance while pedalling, the torque sensor is one of the main parts to check. Inspect the connector first, then retest the bike before ordering a replacement.
Will replacing the sensor fix an E22 error?
In most cases, yes. E22 usually points to a mechanical fault inside the torque sensor assembly. If the error remains after checking the connection and there is no obvious damage elsewhere, replacing the sensor will usually resolve it.
Do I need a mechanic to fit the new sensor?
If you are comfortable with basic maintenance, you can usually do it at home. The main thing to watch for is the correct removal and refitting of the crank assembly, along with any small shim washers inside the assembly.
Shop Replacement Torque Sensors
MAD Bicycle Spares stocks SR Suntour HESC torque sensors for Carrera and Raleigh e-bikes.
4-Pin Torque Sensor — £39.99
6-Pin Torque Sensor — £44.99
View all SR Suntour HESC torque sensors