What this code means
B1237 may indicate a passenger-side air mix control motor circuit short, where the climate control unit may not be receiving a believable position signal from that circuit.
What the vehicle may do
- Passenger-side temperature control may not respond correctly.
- The passenger side may deliver air that is warmer or cooler than requested.
- The fault may be noticed during climate control self-diagnosis even if the symptom is intermittent.
Possible fault areas
- Possible wiring or connector issues in the passenger air mix control motor circuit.
- Possible passenger air mix control motor issue.
- Possible climate control unit issue.
Diagnostic path
Code meaning and approach
B1237 on this Accord points to a passenger-side air mix control motor circuit short. In plain terms, the climate control unit may not be seeing a believable position signal from the passenger air mix motor circuit. The customer may notice poor passenger-side temperature control, the passenger side may not respond as expected, or the fault may only show up during self-diagnosis. The broad possible areas are the passenger air mix motor, its wiring and connectors, and the climate control unit. If other short-circuit codes are present at the same time, keep in mind there may be an open or a short to body ground in the power, 5 V, circuit. Don’t skip that context before chasing this one by itself.
Confirm the fault first
Start by confirming the code. Clear the DTC with the HDS. Cycle the ignition to LOCK (0) and then back to ON (II), or use the engine start/stop button to go from OFF mode back to ON mode. Then run the self-diagnostic function with the HDS or through the climate control unit, and check the codes again. If B1237, or 44, comes right back, continue into the circuit checks. If it does not return, treat it as an intermittent failure and check for loose wires or poor connections in the passenger’s air mix control motor circuit.
Check the S 5V line for an open
With the ignition in LOCK (0), or the vehicle in OFF mode, disconnect the climate control unit 32P connector and the passenger’s air mix control motor 7P connector. Now check continuity on the S 5V, or S5V, wire between climate control unit 32P connector No. 24, the black wire, and passenger’s air mix control motor 7P connector No. 1, also the black wire. If you have continuity, that wire is not open, so 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 for a short between signal and sensor common
Next, keep both connectors disconnected and the ignition still in LOCK (0) or OFF mode. Check continuity between the AMD-P AS circuit and the SENSOR COM circuit at the climate control unit connector. That is climate control unit 32P connector No. 11, the purple wire, to climate control unit 32P connector No. 22, the blue wire. If there is continuity, repair the short in the wires between the climate control unit and the passenger’s air mix control motor. If there is no continuity, those two circuits are not shorted together, and you continue to the next short check.
Check the signal line for a short to ground
Now check the AMD-P AS line to body ground. Use climate control unit 32P connector No. 11, the purple wire, to body ground, with the same disconnected connector condition and the ignition in LOCK (0) or OFF mode. If there is continuity, repair the short to body ground in the wire between the climate control unit and the passenger’s air mix control motor. If there is no continuity, the AMD-P AS wire checks OK, so go on to testing the motor itself.
Check motor resistance on S5V and SENS-COM
For the first motor internal resistance check, measure between passenger’s air mix control motor terminal No. 1 and terminal No. 3, with the ignition in LOCK (0) or OFF mode and both the climate control unit 32P connector and motor 7P connector disconnected. The expected resistance is 6 kΩ±1.8 kΩ. If the resistance is in that range, continue to the next motor movement and signal check. If it is not, replace the passenger’s air mix control motor.
Move the motor and watch the signal resistance
Reconnect the passenger’s air mix control motor 7P connector, but leave the climate control unit 32P connector disconnected. Apply battery power and ground to the motor drive terminals, then reverse the connections, using terminal A at climate control unit 32P connector No. 17, the light green wire, and terminal B at climate control unit 32P connector No. 18, the blue wire. Be careful here: applying power and ground incorrectly can damage the motor. When the motor stops running, disconnect battery power immediately. Then measure resistance between climate control unit 32P connector No. 11, the purple wire, and No. 22, the blue wire. The resistance should change between about 0－6 kΩ±1.8 kΩ. Also remember that continuity between AMD-P AS and SENSOR COM may disappear when the motor is turned to the stop, and normally the climate control unit does not drive the motor to the stop. If the resistance changes as expected, replace the climate control unit. If it does not, replace the passenger’s air mix control motor.
Takeaway
The clean way through B1237 is to confirm the code first, prove the S5V feed is not open, prove the AMD-P AS signal is not shorted to sensor common or ground, and then use the motor resistance checks to separate a motor fault from a climate control unit fault. For more diagnostic training, visit stepdiagnostics.com.
Final check
This diagnosis often comes down to separating wiring faults from a motor feedback problem or a possible control unit issue.
For more guided automotive diagnostics, visit STEP Diagnostics.
