Overview
E.02 – .21 on a Baxi 200/400 combi is a permanent fault code that the boiler is reporting because the configuration jumper labelled “Jumper 3” is not in the expected position. On these boilers certain functions and modes are selected by small jumpers on the PCB; if one is moved, missing, or in the wrong position the boiler will detect the mismatch and lock out to protect itself. This is classed as a permanent configuration fault rather than a simple temporary sensor glitch, so the boiler will usually remain inhibited until the jumper setting is corrected or a qualified engineer resets the configuration. Why it can occur: the jumper may have been moved during a previous service, repair, or replacement of the PCB, by accidental tampering, or because the wrong PCB or accessory was fitted. Severity is medium — the boiler will likely be out of service for heating and/or hot water while it shows the code, but the underlying issue can be a straightforward configuration change rather than a serious mechanical failure. Because the change involves internal electronics and affects safe operation, correcting the jumper is only suitable for someone competent with electrical isolation and gas appliance safety; most homeowners should call a Gas Safe registered engineer or the installer/manufacturer if unsure.
Possible Cause: Jumper 3 changed – check position of jumper 3.
Troubleshooting Steps
Safety precautions:
- If you smell gas, leave the property immediately, do not operate electrical switches, and call the gas emergency number. Do not attempt any checks.
- Isolate electrical power at the consumer unit before working on the boiler. Switch off the boiler at its electrical isolator and at the mains fuse if you are going to remove the casing.
- If you can turn off the gas supply to the boiler safely, do so at the appliance isolator or the meter. If you are not certain how, leave the gas supply alone and call a qualified engineer.
- Only proceed if you are competent with basic electrical isolation and are comfortable removing the boiler casing. If the boiler is under warranty or you are unsure, call a Gas Safe engineer instead.
Initial homeowner checks (safe, non-invasive):
1. Note the exact code displayed (E.02 - .21) and the boiler model and serial number.
2. Try a single reset: press and hold the reset button for 5–10 seconds or use the control dial reset procedure. If the code clears and does not return, monitor the boiler for a short period. Do not keep resetting repeatedly if the code returns.
3. Check basic operating conditions: confirm the gas supply to the property is on (check other gas appliances), check system water pressure is in the normal range (aim for about 1–1.5 bar; if below 0.5 bar the boiler may not run), and ensure external flues and terminals are not blocked. These checks won’t fix an actual jumper misconfiguration but rule out simple reasons for lockout.
4. Ask whether the boiler has recently had work done, a PCB replaced, or been moved — if yes, tell the engineer that a jumper configuration may have been altered.
Specific diagnostic and fix steps (for competent persons only):
1. Isolate electrical supply at the mains and turn off the boiler’s electrical isolator. If you will be touching gas components, isolate the gas supply as well. Ensure the boiler is cool.
2. Remove the outer casing following the manufacturer’s instructions to expose the control PCB. Keep screws safe and avoid damaging wiring.
3. Locate the configuration jumpers on the PCB. Consult the boiler’s service manual or wiring diagram to identify the correct physical location and the correct factory position for Jumper 3 (some manuals label them J1, J2, J3 or similar). Do not guess the correct position — use the official documentation.
4. Inspect Jumper 3: check if it is present, if the shunt is bridging the correct pins, and that it is firmly seated. If it is visibly in the wrong position and you are confident you have the correct jumper map from the manual, move it to the correct position.
5. Visually inspect the PCB for sign of damage, burnt components, or loose connectors around the gas valve and air/gas unit. If any damage is apparent, do not power up — call an engineer.
6. Refit the casing, restore electrical power and gas, and attempt a single reset of the boiler. Observe whether the E.02 – .21 code clears and whether the boiler operates normally for heating and hot water.
7. If the code persists after returning Jumper 3 to the correct position, or if Jumper 3 was already correct, switch the boiler off and contact a Gas Safe registered engineer. The fault may indicate a failed PCB, damaged jumper header, incorrect PCB version, or other internal fault that requires professional diagnosis and possibly parts replacement.
When to call a professional:
- If you are not competent to isolate and work on electrical/gas appliances, do not open the boiler; call a Gas Safe registered engineer.
- If you cannot find correct jumper positions in the manual, or the jumper is missing or the header is damaged, call a Gas Safe engineer or Baxi-approved service agent.
- If the fault returns after correcting the jumper, or if any signs of PCB damage are present, do not continue testing — arrange a professional visit.
Additional notes:
- Do not repeatedly reset the boiler if the fault returns; repeated resets can cause further issues and will not fix a misconfigured jumper.
- If the boiler is under warranty, contact Baxi or your installer before carrying out internal changes — incorrect DIY work may void warranty coverage.
- Only a Gas Safe registered engineer should carry out repairs that involve the gas valve, burner, or replacement of PCB components.
Helpful Resources
Boiler Manual
Download the official PDF manual for the Baxi 200 / 400 Combi Gas Boiler.