What this code means
B1228 may indicate a short in the outside air temperature sensor circuit used by the climate control unit.
What the vehicle may do
- The outside temperature display may be incorrect.
- Automatic climate control operation may not match actual outside conditions.
- The code may be intermittent if a connector or wiring contact is loose.
Possible fault areas
- Outside air temperature sensor circuit wiring
- Connector condition at the sensor or climate control unit
- Outside air temperature sensor
- Climate control unit
Diagnostic path
Opening and code meaning
On this Accord, B1228, or indicator 06, means the climate control unit has detected a short in the outside air temperature sensor circuit. In plain terms, the climate control unit may be seeing that temperature input pulled where it should not be. The driver may notice an incorrect outside temperature display, or climate control behavior that does not match actual conditions. The possible fault areas are the outside air temperature sensor circuit wiring, connector condition, the sensor itself, and, only after the circuit and sensor check out, the climate control unit. The diagnostic path is simple: prove the code is active first, then separate a wiring short from a sensor or control unit fault.
Confirm the code is active
Start by clearing the DTC with the HDS. Then cycle the ignition from LOCK (0) back to ON (II), or use the engine start/stop button to go from OFF mode back to ON mode. Run the self-diagnostic function with the HDS or through the climate control unit, then check for DTCs again. If B1228, or indicator 06, comes right back, continue to the circuit checks. If it does not come back, treat it as an intermittent failure and inspect for loose wires or poor connections in the outside air temperature circuit.
Check the TAM line for a short to ground
Next, check whether the TAM line is shorted to body ground. Turn the ignition to LOCK (0), or select OFF mode. Disconnect the climate control unit 32P connector and the outside air temperature sensor 2P connector. With both connectors disconnected, check continuity between the climate control unit 32P connector No. 27, the BRN wire, and body ground. If there is continuity, repair the short to body ground in the wire between the climate control unit and the outside air temperature sensor. If there is no continuity, the TAM wire is not shorted to ground, so move to the next circuit check.
Check for a short between TAM and SENSOR COM
Now check for a short between the TAM line and the SENSOR COM line. Keep the ignition in LOCK (0), or OFF mode, with the climate control unit 32P connector and the outside air temperature sensor 2P connector still disconnected. Check continuity between the climate control unit 32P connector No. 22, the BLU wire, and the climate control unit 32P connector No. 27, the BRN wire. If there is continuity, repair the short in the wires between the climate control unit and the outside air temperature sensor. If there is no continuity, the TAM and SENSOR COM wires have passed these short checks, so continue to the sensor check.
Check the outside air temperature sensor
At this point, test the outside air temperature sensor. If the sensor does not test OK, replace the outside air temperature sensor. If the sensor does test OK, and the previous wiring short checks also passed, replace the climate control unit.
Verify and close
After the repair, use the same confirmation routine: clear the code, cycle the ignition or power mode, run the self-diagnostic function, and confirm B1228 or indicator 06 does not return. The takeaway is simple: prove the code is current, eliminate shorts on the TAM circuit and between TAM and SENSOR COM, then make the sensor-versus-control-unit decision only after those circuit checks are clean. For more diagnostic training, visit stepdiagnostics.com.
Final check
This diagnosis can separate an active wiring short from a possible sensor or control unit fault by following the short checks before making the final component decision.
For more guided automotive diagnostics, visit STEP Diagnostics.
