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Home >> Mercury >> 1997 >> Cougar/XR7 V8-4.6L VIN W >> Repair and Diagnosis >> Powertrain Management >> Computers and Control Systems >> Testing and Inspection >> Pinpoint Tests >> HW - Evaporative Emission (EVAP) - Purge Flow System >> HW21 - HW30

HW21 - HW30





HW21 - Check EVAP Canister Purge Valve Resistance

- Disconnect EVAP canister purge valve.
- Measure EVAP canister purge valve resistance.

Is the resistance between 30 and 90 ohms?

YES GO to HW22.
NO REPLACE damaged EVAP canister purge valve. RESTORE vehicle. GO to HW42. HW41 - HW43

HW22 - Check EVAP Canister Purge Circuit For Short To VPWR In Harness

- Install breakout box, leave PCM disconnected.
- Measure resistance between PCM test pin 67 or PCM test pin 56 and PCM test pin 71.

Is resistance greater than 10,000 ohms?

YES REPLACE PCM. RESTORE vehicle.

Access the EVAPPDC PID on the scan tool. DRIVE vehicle (including a steady accelerator speed over 80 km/h (50 mph) until the 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.

NO REPAIR short circuit. RESTORE vehicle. COMPLETE PCM Reset to clear DTCs.

Access the EVAPPDC PID on the scan tool. DRIVE vehicle (including a steady accelerator speed over 80 km/h (50 mph) until the 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.

HW23 - Check Evaporative Emission System Leak Through Evaporative Emission Service Port

Odors in the engine compartment or near the exhaust system and stalls can be associated to the evaporative emission system. Possible causes:
- After-market parts and accessories not conforming to evaporative system specifications.
- Leaks in the evaporative emission system.
- Blockages in the evaporative emission system.

- Remove atmospheric vent cap (blue or black) on EVAP canister(s) or canister vent line.
- Plug (or tape) open vent on EVAP canister(s).
- Disconnect and plug fuel vapor hose to PF sensor (or EVAP canister purge valve) from intake manifold at the intake manifold vacuum source.
- Locate evaporative emission test port (marked EVAPORATIVE SERVICE PORT) between EVAP canister purge valve and EVAP canister. If vehicle does not have a test port, GO to step HW24.
- Access the Rotunda Evaporative Emission System Tester 134-00056 or equivalent, including the compressed gas source (nitrogen or argon) and pressure regulator.
- Perform a Tester Self-Test using the instructions provided with the Tester Kit.
- Regulate the gas pressure on the Tester to 6.74 kPa (27 in-H 20).
- Install the Rotunda Evaporative Emission System Tester to the test port and follow the system leak test instructions provided with the Tester Kit.
- If the pressure is not between 6.46 and 6.97 kPa (26 and 28 in-H 20), use the ultra-sonic leak detector provided with the Tester Kit to check for leakage at the vehicle's fuel filler cap and filler pipe assembly.

Is a leak indicated?

YES REMOVE and VERIFY fuel filler cap according to original equipment specifications. REPLACE damaged fuel filler cap. REINSTALL fuel filler cap and TIGHTEN cap only one eighth turn so that cap initially clicks by sound or touch. REPEAT evaporative emission system leak test using Tester. If the leak is still present, REPAIR or REPLACE fuel tank, fuel filler pipe, fuel vapor valve or fuel vapor hose between fuel tank and EVAP canister as necessary. RESTORE vehicle. VERIFY a symptom no longer exists.
NO GO to HW24.

HW24 - Check Evaporative Emission System Using Rotunda Evaporative Emission System Tester

- Remove the fuel filler cap.
- Install the Rotunda Evaporative Emission System Tester 134-00056 or equivalent, including the compressed gas (nitrogen or argon) and pressure regulator. Tester kit contains all required adapters (Schrader valve and fuel filler cap per vehicle application).
- Key on, engine oft.
- For Mustang only: cycle the valve open through output test mode with the scan tool (or disconnect valve harness connection and energize valve using a voltage source).
- Pressurize the vehicle evaporative emission system at 6.74 kPa (27 in.-H20) using the Evaporative Emission System Tester and the instructions that come with the tester.

Is a system leak indicated by the tester red light on?

YES ALLOW the two-position control on the tester to provide a continuing flow of the gas to the closed evaporative emission system. MAINTAIN 6.74 kPa (27 in.-H 20) pressure on the system (monitor tester pressure gauges). GO to HW25.
NO REMOVE Evaporative Emission System Leak Tester. COMPLETE PCM Reset to clear DTCs. Access the EVAPPDC PID on the scan tool. DRIVE vehicle (including a steady accelerator speed over 80 km/h (50 mph) until the 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.

HW25 - Check For Fuel Vapor Hose Restrictions Between EVAP Canister Purge Valve, Fuel Tank And EVAP Canister

- Key on, engine off.
- Disconnect and plug the fuel vapor hose from the EVAP canister(s) at EVAP canister purge valve.
- Reinitiate pressurizing of vehicle evaporative emission system using the Rotunda Evaporative Emission System Tester. Refer to Step HW24 for pressurizing instructions.
- When pressure on the evaporative emission system is stabilized close to 6.74 kPa (27 in-H 20), record the reading.
Remove the plug at the fuel vapor hose to EVAP canister at the EVAP canister purge valve.
- Observe pressure gauges on tester.

Does the pressure immediately drop?

YES REMOVE plugs. REINSTALL the dust cap (blue or black) on EVAP canister or canister vent line at canister. RESTORE vehicle. GO to HW42. HW41 - HW43
NO REMOVE blockages and STRAIGHTEN fuel vapor tubes/hoses between fuel tank, EVAP canister purge valve and EVAP canister(s). REMOVE plugs. REINSTALL the dust cap (blue or black) on EVAP canister. RESTORE the vehicle. GO to HW42. HW41 - HW43

HW27 - DTC P1444: Check PF Sensor Low Voltage To PCM

Continuous Memory Diagnostic Trouble Code (DTC) P1444 indicates that Self-Test has detected a PF sensor circuit input below the minimum. Possible causes:
- PF sensor circuit short to PWR GND.
- VPWR open circuit.
- Damaged purge flow (PF) sensor.
- Damaged PCM.

- Disconnect PF sensor.
- Check for loose pins or broken wires by pulling moderately on the VPWR circuit at PF sensor harness connector.
- Repair as necessary.
- Reconnect PF sensor.
- Connect scan tool.
- Key on, engine running.

NOTE: PF sensor input range to the PCM is 0.40 to 4.80 volts.

- Access EVAPPF PID.
- Key off.

Was EVAPPF PID voltage less than 0.40 volt?

YES For EVAPPF PID voltage between 0.20 and 0.40 volt: GO to HW28.
For EVAPPF PID voltage less than 0.20 volt: GO to HW3O.
NO Fault is an intermittent DTC P1444. GO to HW32.HW31 - HW40

HW28 - Check For Open VPWR Circuit In The PF Sensor

- Disconnect PF sensor.
- Allow the vehicle and PF sensor to cool down or warm up to room temperature 13°C to 27°C (550 F to 80°F) before taking a resistance measurement on the PF sensor. This can take 15 to 20 minutes.
- Measure resistance between VPWR pin and PF, PWR GND pins on the PF sensor.
Is resistance greater than 160 ohms between VPWR and PF pins or greater than 190 ohms between VPWR and PWR GND pins?

YES REPLACE damaged PF sensor. RESTORE vehicle. RECORD data from this Pinpoint Test Step. GO to HW42. HW41 - HW43
NO GO to HW29.

HW29 - Check VPWR For Open In Harness

- Install breakout box, leave PCM disconnected.
- Measure resistance of VPWR circuit between PCM test pin 71 and PF sensor harness connector.

Is resistance less than 5.0 ohms?

YES LEAVE breakout box installed.

For DTC P1444: GO to HW30.
For DTC P1445: GO to HW34. HW31 - HW40
NO REPAIR open circuit. RESTORE vehicle. VERIFY a symptom no longer exists. COMPLETE PCM Reset to clear DTCs. RERUN Quick Test.

HW30 - Check For Short To PWR GND Circuit In PF Sensor

- Disconnect PF sensor.
- Allow the vehicle and PF sensor to cool down or warm up to room temperature (13°C to 27°C (550 F to 80°F)) before taking a resistance measurement on the PF sensor. This can take 15 to 20 minutes.
- Measure resistance between PWR GND and PF pins on the PF sensor.

Is resistance less than 25.50 ohms?

YES REPLACE damaged PF sensor. RESTORE vehicle. GO to HW42. HW41 - HW43
NO GO to HW31. HW31 - HW40

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