Note. For circuit reference (Схема №11)
Note. EVAP Diagnostic Station (P/N J41413 ), or similar, is necessary for accurate diagnostics of EVAP system. This tool will be necessary for vacuum and pressurized leakdown testing of EVAP systems. It is equipped with 2 additional gauges to measure vacuum in inches of mercury (in. Hg), and to measure vapor flow in inches of water (in. H2O), within an EVAP circuit.
Circuit Description
EVAP emission system is checked by applying vacuum to the EVAP system and monitoring for a vacuum leak. PCM monitors vacuum level via fuel tank pressure sensor signal. When appropriate, EVAP canister purge valve and EVAP canister vent solenoid are turned on, allowing engine to draw a small vacuum on the entire evaporative emission system. After the desired vacuum level has been achieved, EVAP canister purge valve is turned off, sealing the EVAP system. If a large leak is detected, DTC P0446 will be set under the following conditions.
Conditions required to set DTC are
- No MAP, TPS, IAT, ECT, EGR, EVAP, VSS or system voltage DTCs set.
- BARO is greater than 72.3 kPa.
- Start-up IAT and ECT is greater than 38°F (3.5°C).
- Difference between ECT and IAT at start up is less than 12.2°F (6.75°C).
- Fuel tank level sensor reads 10-90%.
- Fuel tank vacuum is greater than 15.35 in. H2O.
- Difference between the actual fuel tank pressure and the expected fuel tank pressure is less than the PCM's expectations.
The above conditions are met, and the following is met once
- Fuel tank vacuum is greater than 15.35 in. H2O.
Diagnostic Aids
Check gas cap, vacuum canister and EVAP hoses, lines and EVAP components for damage. Check for faulty connections or damaged harness. Observe EVAP system components displayed on scan tool while moving all related harnesses and connectors. A change in scan tool display indicates fault location. If DTC cannot be duplicated, check scan tool FAILURE RECORDS and FREEZE FRAME data to determine mileage since last DTC was set.