What this code means
B1236 may indicate that the climate control unit is seeing a possible problem with passenger-side air mix control motor feedback.
What the vehicle may do
- Passenger-side temperature control may be incorrect, stuck, or inconsistent.
- The HVAC system may not respond as expected on the passenger side.
Possible fault areas
- Possible passenger air mix control motor issue.
- Possible open, short, loose connection, or poor connection in the related circuit.
- Possible climate control unit involvement.
Diagnostic path
Code meaning and first check
On this Accord, B1236 is a climate control code tied to the passenger-side air mix control motor feedback circuit. In plain terms, the climate control unit may be commanding air temperature movement on the passenger side, but the feedback signal may not make sense. The customer may notice passenger temperature control that is incorrect, stuck, or inconsistent. Broadly, this can involve the passenger air mix motor, its feedback and sensor circuits, connector issues, or the climate control unit. Start by clearing the DTC with the HDS. Turn the ignition switch to LOCK (0), then back to ON (II), or press the engine start/stop button to select OFF mode, then ON mode. Run the self-diagnostic with the HDS or the climate control unit, then check for DTCs. If B1236 or 43 comes back, continue with the circuit checks. If it does not come back, treat it as an intermittent fault and check for loose wires or poor connections in the passenger's air mix control motor circuit.
Check the feedback signal wire for an open
Next, power the vehicle down: ignition switch in LOCK (0), or engine start/stop in OFF mode. Disconnect the climate control unit 32P connector and the passenger's air mix control motor 7P connector. Check continuity on the AMD-P AS/AMD-P-AS line between climate control unit 32P connector No. 11, PUR, and passenger's air mix control motor 7P connector No. 2, BRN. If you have continuity, that wire is OK and you move on. If you do not have continuity, repair the open between the climate control unit and the passenger's air mix control motor.
Check the sensor common wire for an open
With the same connectors still disconnected and the vehicle still in LOCK (0) or OFF mode, check the SENSOR COM/SENS-COM line. Measure continuity between climate control unit 32P connector No. 22, BLU, and passenger's air mix control motor 7P connector No. 3, RED. If there is continuity, that circuit is OK and the next step is the short check. If there is no continuity, repair the open between the climate control unit and the passenger's air mix control motor.
Check for a short between the 5-volt circuit and feedback line
Now check whether the S 5V/S5V line is shorted to the AMD-P AS/AMD-P-AS line. With the climate control unit 32P connector still disconnected and the passenger's air mix control motor 7P connector still disconnected, check continuity between climate control unit 32P connector No. 11, PUR, and climate control unit 32P connector No. 24, BLK. If there is continuity, repair the short in the wiring between the climate control unit and the passenger's air mix control motor. If there is no continuity, those two lines are not shorted together, and you move into the motor resistance checks.
Check motor internal resistance between S5V and SENS-COM
With the ignition still at LOCK (0) or OFF mode, and both the climate control unit 32P connector and passenger's air mix control motor 7P connector disconnected, measure resistance inside the passenger's air mix control motor between motor terminal No. 1 and motor terminal No. 3. The expected resistance is 6 kΩ±1.8 kΩ. If the reading is 6 kΩ±1.8 kΩ, continue to the sweep-style resistance check. If it is not 6 kΩ±1.8 kΩ, replace the passenger's air mix control motor.
Check whether feedback resistance changes as the motor moves
For the final circuit check, reconnect the passenger's air mix control motor 7P connector, while leaving the climate control unit 32P connector disconnected. Connect battery power and ground to terminals A and B, then reverse the connections. Terminal A is climate control unit 32P connector No. 17, LT GRN. Terminal B is climate control unit 32P connector No. 18, BLU. Be careful here: incorrectly applying power and ground to the motor will damage it. Follow the terminal directions carefully, and when the motor stops running, disconnect battery power immediately. Measure resistance between climate control unit 32P connector No. 11, PUR, and climate control unit 32P connector No. 24, BLK. The resistance should change between about 0－6 kΩ±1.8 kΩ. One note: continuity between S 5V and AMD-P AS may disappear when the motor is turned to the stop, and the climate control unit usually does not turn the motor to the stop. If resistance changes between about 0－6 kΩ±1.8 kΩ, replace the climate control unit. If resistance does not change between about 0－6 kΩ±1.8 kΩ, replace the passenger's air mix control motor.
Verify the repair
Keep verification separate from the component testing. After the repair is made, clear the DTC, cycle the ignition or power mode off and back on, run the self-diagnostic again, and confirm B1236 stays gone. The takeaway is simple: prove the feedback and sensor common wiring first, rule out a short on the 5-volt and feedback lines, then use the motor resistance checks to decide whether the fault is in the passenger air mix motor or the climate control unit. For more diagnostic training, visit stepdiagnostics.com.
Final check
This code is often diagnosed by checking whether the commanded passenger air mix movement and the feedback circuit agree, then separating wiring faults from motor or control-unit faults.
For more guided automotive diagnostics, visit STEP Diagnostics.
