What does B0174 mean on a Chevy?

B0174. Upper output air temperature sensor reads out of range. The HVAC module ignores the duct reading and sets a body warning light. Applies to Chevrolet, GMC, Buick, Cadillac, Pontiac, Oldsmobile and Saturn models that use this code.

What causes B0174 on a Chevy?

Upper output air temperature sensor element drifted out of range Open in the upper output air temperature sensor signal circuit Corroded or loose upper output air temperature sensor connector Upper output air temperature sensor contaminated in the duct Faulty input inside the HVAC control module

How do I fix B0174 on a Chevy?

Confirm the code with a scan tool and watch the upper output air temperature reading Inspect and reseat the upper output air temperature sensor connector Test the upper output air temperature sensor resistance against the service chart Move the mode door through its range and watch for a jump in the reading Replace the upper output air temperature sensor only if it reads out of range, then clear the code and retest

Code

B0174

Upper output air temperature sensor reads out of range

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

B0174. Upper output air temperature sensor reads out of range. The HVAC module ignores the duct reading and sets a body warning light. This Chevy-enhanced code applies to Chevrolet, GMC, Buick, Cadillac, Pontiac, Oldsmobile and Saturn models that use this code.

Findings, check these first

Upper output air temperature sensor element drifted out of range
Open in the upper output air temperature sensor signal circuit
Corroded or loose upper output air temperature sensor connector
Upper output air temperature sensor contaminated in the duct
Faulty input inside the HVAC control module

Standard procedure

Confirm the code with a scan tool and watch the upper output air temperature reading
Inspect and reseat the upper output air temperature sensor connector
Test the upper output air temperature sensor resistance against the service chart
Move the mode door through its range and watch for a jump in the reading
Replace the upper output air temperature sensor only if it reads out of range, 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 B0174 definition | OBDII.pro
live manufacturer definition (obdii.pro)
Supports: GM manufacturer meaning for B0174
Fetched directly. The GM entry is the brand-family meaning used here. This site is independent of engine-codes and autocodes.
B0174 CHEVROLET Output Air Temperature Sensor 1 Circuit Range/Performance | 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.
B0174 CHEVROLET Output Air Temperature Sensor 1 Circuit Range/Performance | 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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