P0442 on GMC vehicles
EVAP Small Leak Detected — what it means on a GMC, whether it's safe to drive, and the fixes by model and year.
P0442 on a GMC means evap small leak detected. Most vehicles stay drivable short-term, but diagnose it promptly. The most common cause is loose, worn, or cross-threaded fuel cap (typically $15–$60). Pick your GMC model below for its known failure patterns, recalls, and TSBs.
What does P0442 mean on a GMC?
P0442 is set when the EVAP system's small-leak monitor detects an opening approximately 0.040 inches (1.0 mm) or larger. This is the equivalent of the gas cap being left slightly loose or a small crack in a vent hose. The vehicle remains fully drivable and consumes no extra fuel, but the EVAP system can no longer hold the sealed vacuum required for compliance.
P0442 is a standardized OBD-II code, so its definition is the same on every GMC. What differs by model and engine is which cause is most likely — pick your GMC model below for a diagnosis tuned to its known failure patterns, recalls, and TSBs.
Is it safe to drive a GMC with P0442?
In most cases a GMC stays drivable for short trips with P0442 active, but diagnose and repair it promptly. This is a low-severity code — ignoring it can lead to further damage or a failed emissions test. Exact tolerance depends on the model and engine.
What causes P0442 on a GMC?
| Cause | Likelihood | Estimated repair (USD) |
|---|---|---|
| Loose, worn, or cross-threaded fuel cap | Most common | $15–$60 |
| Aged or split EVAP hose | Common | $30–$200 |
| Failing purge or vent valve seal | Common | $80–$350 |
| Cracked EVAP charcoal canister | Occasional | $200–$600 |
| Damaged O-rings at hose-to-canister or hose-to-solenoid connections | Occasional | $20–$120 |
| Pinhole or seam leak in the fuel filler neck | Occasional | $150–$600 |
| Failed fuel tank vent at the tank top (less accessible to inspect) | Rare | $300–$900 |
Repair costs are typical US ranges and vary by GMC model, model year, and labor rate. A diagnostic trouble code is a symptom, not a guaranteed failed part — confirm the root cause before replacing anything.
P0442 by GMC model
Select your GMC model and year for a P0442 diagnosis tuned to that vehicle's failure patterns, recalls, and TSBs.
GMC Sierra 1500
988 NHTSA owner complaints · 14 recalls on record across the years covered below.
Complaint and recall counts are NHTSA totals for the model years covered on this site, not counts specific to P0442.
P0442 on other makes
Other codes on GMC vehicles
P0442 on a GMC: frequently asked questions
What does diagnostic trouble code P0442 mean on a GMC?
P0442 is set when the EVAP system's small-leak monitor detects an opening approximately 0.040 inches (1.0 mm) or larger. This is the equivalent of the gas cap being left slightly loose or a small crack in a vent hose. The vehicle remains fully drivable and consumes no extra fuel, but the EVAP system can no longer hold the sealed vacuum required for compliance. P0442 is a standardized OBD-II code, so the definition is the same on every GMC — which cause is most likely varies by model and engine.
What are the symptoms of P0442 on a GMC?
Check Engine Light is illuminated. Faint fuel smell, especially after refueling on a hot day. No noticeable change in drivability or fuel economy. Vehicle will fail emissions / smog testing
What causes P0442 on a GMC?
Loose, worn, or cross-threaded fuel cap (most-common). Aged or split EVAP hose (common). Failing purge or vent valve seal (common). Cracked EVAP charcoal canister (occasional). Damaged O-rings at hose-to-canister or hose-to-solenoid connections (occasional). Pinhole or seam leak in the fuel filler neck (occasional). Failed fuel tank vent at the tank top (less accessible to inspect) (rare)
Is it safe to drive a GMC with P0442?
In most cases a GMC stays drivable for short trips with P0442 active, but it should be diagnosed and repaired promptly — this is a low-severity code. Ignoring it can lead to further damage or a failed emissions test. Exact tolerance depends on the model and engine.