Note. EVAP Diagnostic Station (J41413) is necessary for accurate diagnosis 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. H 2 O), within an EVAP circuit.
Circuit Description
Evaporative (EVAP) emissions canister purge is controlled by a solenoid valve which allows manifold vacuum to purge canister when energized (purge on) by PCM. A vacuum switch in purge line is used to detect when system is being purged. PCM supplies and reads EVAP purge vacuum switch signal. If switch is open (purge detected) when not commanded by PCM, DTC P1441 is set.
Conditions required to set DTC are
- No ECT, IAT, VSS, MAP, EGR, EVAP, system voltage, vacuum switch or TP sensor DTCs set.
- BARO is more than 72.3 kPa.
- Start-up intake air and coolant temperature readings are 40-95°F (4.2-35°C).
- Difference between ECT and IAT at startup is less than 12.2°F (6.75°C).
- Fuel tank is between 15 percent and 85 percent.
- Fuel tank vacuum is greater than 2 in. H 2 O for 2 seconds.
Diagnostic Aids
Check for poor connection at PCM. Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals and poor terminal connection. Inspect wiring harness for damage. If connections and harness appear okay, observe EVAP VACUUM SW display 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 to determine mileage since last DTC was set.