What this code means
B1228 may indicate that the climate control unit is seeing a possible short condition in the outside air temperature sensor circuit.
What the vehicle may do
- The outside temperature display may be inaccurate.
- HVAC operation can be affected because the climate control unit uses this sensor input.
Possible fault areas
- Possible outside air temperature sensor circuit wiring issue.
- Possible connector or terminal condition issue.
- Possible climate control unit input-side fault area.
Diagnostic path
Opening and code logic
On this 2020 to 2025 Honda CR-V Hybrid, B1228 is for a possible short in the outside air temperature sensor circuit. The climate control unit uses that sensor input for HVAC operation, so the vehicle may show an incorrect outside temperature reading, and climate control behavior can be affected. Broadly, this can involve the sensor circuit wiring, connector condition, or the climate control unit input side. The code sets when the climate control unit sees the outside air temperature sensor input voltage lower than the specified value.
Start clean and confirm the fault
Before going straight into pinpoint testing, start with the basic troubleshooting checks so you are not chasing a symptom caused by a bigger system issue. Then turn the vehicle to ON mode and use the HDS. Go into Body Electrical, then HVAC, then Data List, and use that as your confirmation point for the outside air temperature sensor signal path.
Prepare the circuit for isolation testing
For the short inspection, isolate the circuit first. Disconnect the outside air temperature sensor 2P connector. Then disconnect climate control unit connector A, the 28P connector. At this point, make sure the connector face and terminal identification are confirmed before placing meter leads. If you cannot positively identify the terminals, pause and recheck the earlier diagnostic path instead of guessing.
Check for a short between TAM and SENSOR_COM
With climate control unit connector A disconnected, testing on the female terminal side, and IG Mode OFF, check the TAM and SENSOR_COM wire-to-wire short condition. A normal circuit has more than 1 MΩ. If that check is abnormal, the fault is in the circuit, so stay with the harness and connector side of the diagnosis.
Check TAM for a short to ground
Next, with IG Mode OFF, check TAM for a short to ground. The normal condition is also more than 1 MΩ. Again, an abnormal result points to a circuit problem rather than condemning the control unit right away.
Decision point
Once the circuit checks are reviewed, the decision is straightforward. If the short inspections are abnormal, repair the circuit problem that the testing uncovered. If the other inspection items are normal, the remaining fault area is the climate control unit. Keep that as the last step in the logic, not the first guess.
Verification and takeaway
After the fault area is addressed, verify the repair under the same operating condition and confirm B1228 does not return. The takeaway is simple: isolate the outside air temperature sensor circuit, prove whether TAM or SENSOR_COM is shorted, and only point back to the climate control unit after the circuit checks pass. For more diagnostic training, visit stepdiagnostics.com.
Final check
B1228 is often approached by isolating the outside air temperature sensor circuit first, then only considering the control unit after the circuit checks are normal.
For more guided automotive diagnostics, visit STEP Diagnostics.
