HW41 - HW43

HW41 - Check EVAP Canister Purge Valve Circuit Intermittent Open Or Short

- Install breakout box, leave PCM disconnected.
- Measure resistance between PCM test pin 67 or PCM test pin 56 and PCM test pin 71, while performing the following:
- Lightly tap on the EVAP canister purge valve and observe a resistance change.
- Wiggle the EVAP canister purge valve connector and vehicle harness between the valve and the PCM, observe a resistance change.

Does the resistance reading change to below 30 ohms or above 90 ohms (Mustang) or above 38 ohms (Continental, F-Series/E-Series)?

YES ISOLATE fault and REPAIR as necessary. RESTORE vehicle. COMPLETE PCM Reset to clear DTCs. RERUN Quick Test.
NO UNABLE to duplicate or identify fault at this time. GO to Pinpoint Test Step Z1 with the resistance readings and the resistance readings and list of Possible causes.

HW42 - Verification Of Evaporative Emission System Repair Using Rotunda Evaporative Emission System Leak Tester

- Plug or tape atmospheric vent cap on EVAP canister (if applicable).
- Remove fuel filler cap at fuel filler pipe.
- Install Rotunda Evaporative Emission System Leak Tester 134-00056 or equivalent including the nitrogen or argon gas supply and pressure regulator.
- Disconnect and plug fuel vapor hose to PF sensor (or EVAP canister purge valve on Ranger) from intake manifold at the intake manifold vacuum source.
- Pressurize the EVAP system at 6.74 kPa (27 in-H20) with tester.
- Observe tester installation leak self-test for two minutes and then the EVAP system leak test.
- Listen for a vacuum leak noise and check for substantial fuel vapor odors at isolated areas in the EVAP system.

Does the pressure applied to the EVAP system hold?

YES REMOVE plug and RECONNECT fuel vapor hose from PF sensor (or EVAP canister purge valve) at intake manifold vacuum source. REMOVE EVAP System Leak Tester. REINSTALL fuel filler cap. TIGHTEN cap only one eighth turn so that cap initially clicks by sound or touch. COMPLETE PCM reset to clear DTCs. Access EVAPPDC PID on scan tool. DRIVE vehicle (including a steady accelerator speed over 80 km/h (50 mph) until EVAPPDC PID shows 75 percent duty cycle). Then maintain approximate speed until duty cycle reaches zero percent. After additional two minute drive, bring vehicle to an idle. RERUN Quick Test. VERIFY a symptom no longer exists.
NO GO to HW43.

HW43 - Check Location Of Evaporative Emission System Pressure Leak

- Systematically isolate area of potential pressure leak.
- Close off pressure to EVAP system.
- Disconnect and plug fuel vapor hose from fuel tank at EVAP canister.
- Apply controlled pressure at 6.74 kPa (27 in-H2O to the EVAP system with the leak tester.
- If pressure now holds, GO to Powertrain, Emissions Control Systems for EVAP canister diagnosis.
- If system presure cannot hold, close pressure supply to system.
- Disconnect and plug fuel vapor hose from EVAP canister at EVAP canister purge valve.
- Again, apply controlled pressure to the EVAP system.

Does the pressure hold?

YES REMOVE plugs. RECONNECT fuel vapor hose at EVAP canister. RETURN to Pinpoint Test Step HW14 to check EVAP canister purge valve integrity on Ranger or Pinpoint Test Step HW18 to check EVAP canister purge valve integrity on Mustang. REMOVE EVAP System Leak Tester. REINSTALL fuel filler cap. COMPLETE PCM reset to clear DTCs. Access EVAPPDC PID on scan tool. DRIVE vehicle (including a steady accelerator speed over 80 km/h (50 mph) until EVAPPDC PID shows 75 percent duty cycle). Then maintain approximate speed until duty cycle reaches zero percent. After additional two minute drive, bring vehicle to an idle. RERUN Quick Test. VERIFY a symptom no longer exists.
NO REMOVE plugs. CHECK for fuel vapor hose cracks or fuel vapor valve damage. EXAMINE and SECURE fuel vapor hose connections to components. REPAIR or REPLACE as necessary. REMOVE EVAP System Leak Tester. REINSTALL fuel filler cap. COMPLETE PCM reset to clear DTCs. Access EVAPPDC PID on scan tool. DRIVE vehicle (including a steady accelerator speed over 80 km/h (50 mph) until EVAPPDC PID shows 75 percent duty cycle). Then maintain approximate speed until duty cycle reaches zero percent. After additional two minute drive, bring vehicle to an idle. RERUN Quick Test. VERIFY a symptom no longer exists.