What this code means
B1236 may indicate that the climate control unit is seeing an open or abnormal passenger air mix control motor signal circuit.
What the vehicle may do
- Passenger-side temperature control may not respond normally.
- Passenger-side air temperature may not match the selected setting.
- The HVAC system can store the code even when the customer complaint is intermittent or not obvious.
Possible fault areas
- Passenger’s air mix control motor area
- Possible wiring or connector issue between the motor and climate control unit
- Possible signal or sensor-common circuit issue
- Possible climate control unit issue
Diagnostic path
Opening context
On this 2018 to 2025 Honda Accord 2.0 Hybrid, B1236 points to the passenger’s air mix control motor circuit being seen as open by the climate control unit. In plain language, the control unit may not be seeing the passenger blend-door position signal the way it expects. The customer may notice poor passenger-side temperature control, the passenger side may not respond normally to temperature commands, or the system may store the code without an obvious complaint. Broadly, this can involve the passenger’s air mix control motor area, the signal and sensor-common wiring between the motor and the climate control unit, connector condition, or the climate control unit itself. Before getting into pinpoint checks, start with the basic system checks and follow a structured diagnostic approach.
How the fault is judged
The logic here is a signal plausibility problem. If the input voltage from the passenger’s air mix control motor is higher than the specified range, the climate control unit judges that as abnormal and stores B1236. Also keep in mind there is no direct standalone test for the motor itself in this path, so the diagnosis works by checking the related circuits and control-unit output first, then using those results to narrow the fault area.
Confirm the code path and check motor-side voltage
First, turn the vehicle to ON mode. Then disconnect the passenger’s air mix control motor 5P connector. With the connector disconnected, work at the female terminals for the passenger’s air mix control motor connector, with IG Mode ON and the unit output voltage inspection ON. The normal result for this check is About 5 V. If that voltage check is normal, the diagnostic path points to a problem with the passenger’s air mix control motor. If it is abnormal, continue looking at the related components and circuits instead of calling the motor yet. Make sure the correct terminal callouts are identified before probing; do not guess at pin locations.
Check the AMD-P-AS and SENS-COM circuits for opens
Next, move to the open-wire checks. Disconnect the passenger’s air mix control motor 5P connector, and disconnect climate control unit connector B, the 24P connector. With IG Mode OFF, check the AMD-P-AS circuit between the disconnected passenger air mix motor connector female terminals and the disconnected climate control unit connector B female terminals. The normal result is less than 1 Ω. Then check the SENS-COM circuit the same way, also with IG Mode OFF. Its normal result is also less than 1 Ω. If either of these checks is abnormal, the path points to a circuit problem. Again, confirm the exact terminals before testing.
Check the climate control unit side and verify
If the circuit checks do not identify the problem, disconnect the passenger’s air mix control motor 5P connector again and leave climate control unit connector B, the 24P connector, connected. With IG Mode ON and the unit internal circuit inspection ON, check the connected climate control unit connector B female terminals. The normal result is About 5 V. If that check is abnormal, the diagnostic path points to a problem with the climate control unit. After the fault found by this path is corrected, keep verification separate from testing: recheck the system operation and confirm B1236 stays gone. The takeaway is simple: prove the motor-side voltage first, prove both signal-related wires are intact, then judge the climate control unit side last. For more diagnostic training, visit stepdiagnostics.com.
Final check
For B1236, the diagnostic direction is to check the related voltage and continuity paths in order before judging the motor area or the climate control unit.
For more guided automotive diagnostics, visit STEP Diagnostics.
