What this code means
B1241 may indicate a problem in the blower motor circuit controlled by the climate control unit.
What the vehicle may do
- The blower motor may not run correctly.
- Blower speed response may be missing or inconsistent.
- The climate control system may store the code during self-diagnosis.
Possible fault areas
- Possible power supply or fuse issues.
- Possible blower motor relay or relay circuit issue.
- Possible blower motor, power transistor, ground, or wiring issue.
- Possible climate control unit involvement after circuit checks pass.
Diagnostic path
Open and confirm the fault
On this Accord, B1241 means the climate control unit is seeing a problem in the blower motor circuit. In the bay, that may show up as a blower that does not respond correctly, does not run, or only behaves under certain conditions. Broadly, this can involve power supply, ground, the blower motor, the relay, the power transistor, the wiring between the climate control unit and the blower circuit, or the climate control unit itself. Start by clearing the code. Cycle the ignition OFF and back ON, then run the self-diagnostic check with the HDS or through the climate control unit. If B1241, or its matching display number, comes right back, continue into the circuit checks. If it does not return, treat it as intermittent and inspect for loose wiring or poor connections in the blower motor circuit before going any deeper.
Check the main blower fuse and power feed
With the ignition OFF, check fuse No. A14, rated at 40 A, in the under-hood fuse and relay box. If the fuse is good, move on to the blower motor power check. If the fuse is open, replace the fuse and recheck the circuit. If that 40 A fuse opens again, repair the short in the No. A14 fuse circuit before continuing. Next, disconnect the blower motor 2P connector, turn the ignition ON, and check for battery voltage between blower motor connector terminal No. 2, the white wire, and body ground. If battery voltage is present, the power feed to the blower is available and the next question is whether the motor can run. If battery voltage is missing here, skip ahead to the blower motor relay side of the diagnosis.
Prove the blower motor and low-side path
Turn the ignition OFF, reconnect the blower motor connector, and use a jumper from blower motor connector terminal No. 1, the green wire, to body ground. Turn the ignition ON. If the blower runs at high speed, the motor can operate and you can keep testing the control side. If it does not run at high speed with that jumper in place, replace the blower motor. After that, turn the ignition OFF, remove the jumper, disconnect the power transistor 4P connector, and check continuity from power transistor terminal No. 3, the black wire, to body ground. If there is continuity, that ground path is OK. If there is no continuity, check for an open between the power transistor and body ground, and if the wire is OK, check for poor ground at G401.
Check the blower motor control wiring through the power transistor
Now jumper power transistor connector terminal No. 3, the black wire, to terminal No. 4, the green wire, and turn the ignition ON. If the blower runs at high speed, the BLW-M wire is OK and you can continue toward the climate control unit wiring. If the blower does not run, repair the open between the power transistor and the blower motor. Turn the ignition OFF, remove the jumper, and leave the power transistor disconnected. Then disconnect the climate control unit 32P connector. Check the BLOWER V, or BLW-V, line from climate control unit terminal No. 15, the blue wire, to body ground. Continuity here means that line is shorted to ground between the climate control unit and the power transistor. No continuity means it is not shorted, so move to the BLOWER G, or BLW-G, line. Check climate control unit terminal No. 14, the yellow wire, to body ground. Again, continuity means a short to body ground between the climate control unit and power transistor. No continuity means that line is not shorted, and you can move into open-circuit checks.
Check for opens between the climate control unit and power transistor
With the climate control unit connector and power transistor connector still disconnected, check continuity on the BLOWER G, or BLW-G, line between climate control unit terminal No. 14, the yellow wire, and power transistor terminal No. 1, also the yellow wire. If there is continuity, that wire is OK. If there is no continuity, repair the open between the climate control unit and the power transistor. Then check the BLOWER V, or BLW-V, line between climate control unit terminal No. 15, the blue wire, and power transistor terminal No. 2, also the blue wire. If there is continuity, that wire is OK and you move to the power transistor check. If there is no continuity, repair the open between the climate control unit and the power transistor.
Check the power transistor decision point
Reconnect the climate control unit 32P connector and test the power transistor. If the power transistor fails the test, replace the power transistor. If the power transistor tests OK after the wiring checks have passed, replace the climate control unit. One important point: if the power transistor is faulty, inspect the blower motor for damage, and replace the blower motor if necessary.
If blower power was missing, check the relay side
If the earlier blower motor connector voltage check did not show battery voltage, turn the ignition OFF and remove the blower motor relay from the under-hood fuse and relay box. Test the relay. If the relay is not OK, replace the blower motor relay. If the relay is OK, keep checking the relay socket feeds. With the ignition OFF, blower motor connector disconnected, and relay removed, check for battery voltage between blower motor relay socket terminal No. 1 and body ground. If battery voltage is present, the +B HTR MTR line is OK. If battery voltage is not present, the +B HTR MTR line is open, and the repair path is replacement of the under-hood fuse and relay box.
Finish the relay control and ground checks
Next, turn the ignition ON and check for battery voltage between blower motor relay socket terminal No. 3, the light green wire, and body ground. If battery voltage is present, the IG2 A/C wire is OK. If battery voltage is missing, the path involves an open between the relay circuit board and the blower motor relay in the under-hood fuse and relay box, or between an identified fuse in the under-dash fuse and relay box and the relay circuit board in the under-hood fuse and relay box. The exact fuse identifier for that branch is not available here, so pause, recheck the earlier diagnostic path, and do not guess at the fuse location. If the wiring checks OK on that branch, replace the relay circuit board. Finally, turn the ignition OFF and check continuity between blower motor relay socket terminal No. 4, the black wire, and body ground. If there is continuity, repair the open between the blower motor relay and the blower motor. If there is no continuity, check for an open between the blower motor relay and body ground, and if the wire is OK, check for poor ground at G301.
Verify the repair
Keep the confirmation separate from the circuit testing. After the repair, clear the code, cycle the ignition OFF and back ON, run the self-diagnostic check again, and confirm B1241 stays gone. The takeaway is simple: prove the blower has power, prove the motor can run, then isolate the ground, control, relay, and transistor paths before condemning a module. For more diagnostic training, visit stepdiagnostics.com.
Final check
This diagnosis often works best when the circuit is split into power feed, motor operation, ground, control wiring, relay feed, and final control decisions.
For more guided automotive diagnostics, visit STEP Diagnostics.
