Body, generic

B0173 Upper Left Duct Air Temperature Sensor Circuit

Check engine lightUsually off
EmissionsNot relevant
Drive cycleNot required
Limp modeNo

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.

Likely causes

Duct sensor harness pinched between HVAC case and cross-car beam (GM 17-NA-049)
Upper left duct sensor thermistor open or shorted
HVAC module calibration needing an update (GM PIT5383, 2015 models)

Symptoms

  • Left vents too warm or too cold, or heating or cooling seems not to work
  • Climate control runs on a default duct temperature

Repair estimate

DifficultyMediumDIY possible
Parts and labour€30–300
Time0.5–3 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

discharge air temp sensorhvac control module

Related codes

B0166B0175

References: saabwisonline.com, saabwisonline.com, static.nhtsa.gov, static.nhtsa.gov.