What does B0173 mean on a Chevy?

B0173. Upper output air temperature sensor circuit malfunction. The HVAC module cannot read the duct temperature and sets a body warning. Applies to Chevrolet, GMC, Buick, Cadillac, Pontiac, Oldsmobile and Saturn models that use this code.

What causes B0173 on a Chevy?

Failed upper output air temperature sensor with an out of range element Open or short in the upper output air temperature sensor signal circuit Corroded or loose upper output air temperature sensor connector Upper output air temperature sensor buried in debris in the duct Faulty input inside the HVAC control module

How do I fix B0173 on a Chevy?

Confirm the code with a scan tool and compare the upper output air temperature reading to duct temperature Inspect and reseat the upper output air temperature sensor connector Test the upper output air temperature sensor and its signal circuit against the service chart Repair any chafed or open wiring before condemning the sensor Replace the upper output air temperature sensor only if its reading does not match duct temperature, then clear the code and retest

Code

B0173

Upper output air temperature sensor circuit malfunction

Category: Body
Severity: Body Warning Light
Applies to: Chevrolet, GMC, Buick, Cadillac, Pontiac, Oldsmobile and Saturn models that use this code
Related: No single generic twin. See OBD Codes List

What it means

B0173. Upper output air temperature sensor circuit malfunction. The HVAC module cannot read the duct temperature and sets a body warning. This Chevy-enhanced code applies to Chevrolet, GMC, Buick, Cadillac, Pontiac, Oldsmobile and Saturn models that use this code.

Findings, check these first

Failed upper output air temperature sensor with an out of range element
Open or short in the upper output air temperature sensor signal circuit
Corroded or loose upper output air temperature sensor connector
Upper output air temperature sensor buried in debris in the duct
Faulty input inside the HVAC control module

Standard procedure

Confirm the code with a scan tool and compare the upper output air temperature reading to duct temperature
Inspect and reseat the upper output air temperature sensor connector
Test the upper output air temperature sensor and its signal circuit against the service chart
Repair any chafed or open wiring before condemning the sensor
Replace the upper output air temperature sensor only if its reading does not match duct temperature, then clear the code and retest

Look up another code

Press / to jump to the box. Chevy-enhanced powertrain, body, chassis and network codes.

Sources and review

Review: checked against the recorded source material.

Code B0173 definition | OBDII.pro
live manufacturer definition (obdii.pro)
Supports: GM manufacturer meaning for B0173
Fetched directly. The GM entry is the brand-family meaning used here. This site is independent of engine-codes and autocodes.
B0173 CHEVROLET Output Air Temperature Sensor 1 Circuit | Engine-Codes.com
archived reference page (engine-codes.com via Wayback Machine)
Supports: Chevrolet meaning and possible causes
Fetched directly. Model and year fitment remain curator claims.
B0173 CHEVROLET Output Air Temperature Sensor 1 Circuit | AutoCodes.com
archived reference page (autocodes.com via Wayback Machine)
Supports: corroboration of Chevrolet meaning and causes
Same Chevrolet text as the engine-codes page (both sites share one publisher).

Last updated 2026-10-10.

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