What causes P0172 on a GMC Sierra 1500?

Common causes of P0172 on GMC Sierra 1500: Dirty or faulty MAF sensor over-reporting airflow; Leaking fuel injector(s) causing excess fuel delivery; Stuck-open purge valve dumping fuel vapor into intake; High fuel pressure from a faulty fuel pressure regulator; PCV valve stuck open (common on GM 2.5L LCV and 1.5T engines).

P0172

P0172 GMC Sierra 1500

Q: How much does it cost to fix P0172 on a GMC Sierra 1500?

Fixes for P0172 on GMC Sierra 1500 include: Clean or replace MAF sensor (ACDelco MAF cleaner or replacement), Test and replace leaking fuel injectors, Replace EVAP purge solenoid valve (ACDelco 214-2149), Test fuel pressure and replace regulator if out of spec, Replace PCV valve or PCV valve cover assembly (integrated on some GM engines).

System Too Rich (Bank 1) · Powertrain Code · Medium · Repair: Moderate

What is P0172?

The engine is running rich on bank 1 — too much fuel or not enough air. Common causes include leaky fuel injectors, stuck-open purge valve, or a dirty/faulty MAF sensor.

When the GMC Sierra 1500 triggers code P0172 (system too rich (bank 1)), it typically points to an issue in the powertrain system. Below you'll find the most common causes, symptoms, and repair options specific to the GMC Sierra 1500.

This repair is rated moderate, meaning some experience and specialty tools required.

Diagnostic data on this page is compiled from publicly available repair resources and technical service bulletins. Always have a qualified mechanic confirm the diagnosis before authorizing repairs on your GMC Sierra 1500.

Common Causes on GMC Sierra 1500

Dirty or faulty MAF sensor over-reporting airflow
Leaking fuel injector(s) causing excess fuel delivery
Stuck-open purge valve dumping fuel vapor into intake
High fuel pressure from a faulty fuel pressure regulator
PCV valve stuck open (common on GM 2.5L LCV and 1.5T engines)

Symptoms

Check Engine Light on
Strong fuel smell from exhaust
Black soot deposits on tailpipe
Rough idle
Spark plug fouling
Reduced fuel economy

Recommended Fixes

Clean or replace MAF sensor (ACDelco MAF cleaner or replacement)

Test and replace leaking fuel injectors

Replace EVAP purge solenoid valve (ACDelco 214-2149)

Test fuel pressure and replace regulator if out of spec

Replace PCV valve or PCV valve cover assembly (integrated on some GM engines)

Notes for GMC Sierra 1500

On GM 1.5T and 2.5L engines, the PCV valve is integrated into the valve cover — a stuck PCV valve requires replacing the entire valve cover assembly.

P0172 GMC Sierra 1500

What is P0172?

Common Causes on GMC Sierra 1500

Symptoms

Notes for GMC Sierra 1500

Check GMC Sierra 1500 Specs