B0173Upper Left Duct Air Temperature Sensor Circuit
- Generic OBD-II code · Body
- How the car detects it
- B0173 lacks an entry in the public J2012 lists, but General Motors documents it clearly in its Global A climate control. In the 2011 Saab 9-5 and 9-4X manuals it covers the upper left duct air temperature sensor: B0173 02 when the signal is grounded, 05 for high voltage or an open; the module flags a signal under 0.1 V or over 4.9 V and continues with a default value. B0178 is the lower left sensor, B0509 and B0514 the right side. GM bulletin 17-NA-049 (2017 Bolt EV, Opel Ampera-e) traces B0173 and B0178 to a duct sensor harness pinched between HVAC case and tie bar, and PIT5383 lists B0173 for 2015 models needing new K33 HVAC software. GM files the air inlet door under B022A.
- What you may notice
- Left vents too warm or too cold, or heating or cooling seems not to work
- Climate control runs on a default duct temperature
- Likely causes
- LikelyDuct sensor harness pinched between HVAC case and cross-car beam (GM 17-NA-049)
- PossibleUpper left duct sensor thermistor open or shorted
- RareHVAC module calibration needing an update (GM PIT5383, 2015 models)
- Repair
- Medium · Often possible to do yourself.Typical cost: €30 – €300
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.