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HOMESERVICE MANUALSCHEVROLET2006SUBURBAN C1500, 5.3 ZREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 28 (ENGINE CONTROL SYSTEM - SELF-DIAGNOSTICS)SELF-DIAGNOSTIC SYSTEMSERVICE BAY TESTSEVAP PURGE/SEAL FUNCTION
2006 Chevrolet Suburban C1500, 5.3 Z

EVAP Purge/Seal Function

2006 Chevrolet Suburban C1500, 5.3 ZSECTION EVAP Purge/Seal Function
WARNING: This page is about a different car, the 2003 Pontiac Vibe. However, it is still accessible from the selected car via links, so may be relevant.
NOTE: Ensure vehicle underbody temperature is similar to ambient temperature and allow the surrounding air to stabilize before starting the diagnostic procedure. Fuel tank pressure may increase on a hot vehicle due to thermal expansion of vapors in fuel tank. Fuel tank fill levels can affect the results of the diagnostic procedure. Fuel tank pressure may increase on a warm vehicle that has less than one third a tank of fuel.

EVAP purge/seal function is designed to seal the EVAP system with a vacuum applied. The test allows the technician to monitor Fuel Tank Pressure (FTP) sensor, for any vacuum decay. The purge/seal function can also alert the technician of an inoperable purge, vent, or pressure switching solenoid. When the EVAP purge/seal function is enabled, PCM commands vent and pressure switching solenoids ON (closed). The purge solenoid is commanded ON (open) allowing a vacuum to enter EVAP system. After 30 seconds, PCM commands purge solenoid OFF (closed), sealing the system. EVAP system will remain sealed for 150 seconds. FTP sensor reading should be approximately -12.50 in. H2O. To perform EVAP purge/seal test with the scan tool follow the procedures below:

  1. Run engine to normal operating conditions.
  2. Install scan tool.
  3. Turn ignition switch to RUN position, engine OFF.
  4. Remove fuel fill cap. FTP sensor should read near 0.0 in. H2O.
  5. Install fuel fill cap and start the engine.
  6. Enable EVAP purge/seal function on the scan tool.
  7. FTP sensor reading should decrease to a -12.50 in. H2O, indicating a vacuum has entered the system.
  8. Observe FTP sensor reading for 2 minutes. If there is no evidence of vacuum decay, FTP sensor reading should remain at -12.50 in. H2O.

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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.