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Just picked up my car from the local muffler shop..... Very big smile on my face as I was listening to the "new" flowmaster 40's they just installed!!

Now on to my dilemma.... I still have codeP0455 and I check and tightened the gas cap..... any more suggestions?

Bill T.
92 MTX - Black on Black
96 Med. Graph-Trophy Whore!!
97 Ebony - Sold!! 7/20/08
97 VW - project in the works....
98 SF
K&N Cone Filter
Flowmaster 40's
(203) 650-0533 Cell
Bayshore Able Ford - 2nd place July 07
Blue Oval All Ford - 2nd place Apr. 07
Magnetic Minis Bash - 2nd place July 06



1997 Ford Taurus SHO 3.4L

OBD-II Code Data

P0455   EVAP System Large Leak Detected

Possible Causes

Setting Conditions

  • Aftermarket EVAP hardware non-conforming to specifications
  • Canister vent (CV) solenoid stuck open
  • EVAP canister purge valve stuck closed, or canister damaged
  • EVAP canister tube, EVAP canister purge outlet tube or EVAP return tube disconnected or cracked, or canister is damaged
  • Fuel filler cap missing, loose (not tightened) or the wrong part
  • Loose fuel vapor hose/tube connections to EVAP components
  • Purge sensor or FTP sensor is out of calibration or has failed

Engine started (cold); ECT signal less than 90║F at startup; and the PCM detected several small fuel vapor leaks or a large leak somewhere in the EVAP system.

This code sets in 2 Trip(s).
This code will turn on the
MIL (Malfunction Indicator Lamp)

Malfunction Indicator Lamp

The Malfunction Indicator Lamp (MIL) alerts the driver that the Powertrain Control Module (PCM) or Transmission Control Module (TCM) has detected an OBD II emission-related component or system fault. When this type of malfunction occurs, an OBD Diagnostic Trouble Code (DTC) will be set. The MIL is located on the instrument cluster and is labeled CHECK ENGINE, SERVICE ENGINE SOON, or it is identified with the ISO standard engine symbol (which is a picture of an engine).
Prove-Out Test
The instrument cluster (IC) and other vehicle modules carry out a display prove-out to verify that all module controlled warning/indicator lamps and monitored systems are functioning correctly within the instrument cluster (IC). The instrument cluster (IC) and other modules such as the Powertrain Control Module (PCM) provide a timed prove-out while other indicators illuminate until engine start up. When the ignition switch is cycled to the "on" position with the engine off, the indicators illuminate to prove-out for 3 seconds.
Instrument Cluster (Gateway) Function
The instrument cluster (IC) acts as a gateway module by receiving information in one format and transmitting it to other modules using another format. For example, the instrument cluster (IC) receives the vehicle speed data from the PCM over the HS-CAN, converts the data into a MS-CAN message and sends (gateways) the message to other network modules such as the HVAC module, the tire pressure monitoring system (TPMS), the parking aid module (PAM), and the SJB. This enables network communication between modules that do not communicate using the same network (HS-CAN or the MS-CAN).





1.       Connect the Scan Tool to the data link connector (DLC). Turn the key on and bring up the ECT PID on the Scan Tool.

2.       Start the engine and allow it to run until the ECT PID reaches 130║F (54║C).

3.       Turn to key on, engine off. Use the Scan Tool to clear any stored DTC's and to reset the OSR Monitors. Note that DTC P1000 will appear once all of the trouble codes are cleared. Start the engine without turning off the ignition key.

4.       Drive in stop and go traffic for several minutes. Include at least 4 idle periods that last for 30 seconds each. Bring the vehicle to a stop, but do not turn off the key. Check the status of the Readiness code for the EVAP System Monitor. It should change to YES. If it does, perform any additional driving under the conditions required to run the remainder of the monitors. If the Readiness code does not change to YES, check for any Pending codes in the Generic OBD II section of the Scan Tool. If no Pending codes are set, and the status did not change to YES, return to step 4 and repeat the test procedure.




Copyright 2009 Identifix, Inc. All rights reserved.




1997 Ford Taurus SHO 3.4L


Test Details

Hotline Archive # 323554



Confirmed Fix

Vehicle Application:

1997 Ford Taurus SHO 3.4L



Customer Concern:

Malfunction Indicator Lamp (MIL) on. Trouble code P0455. Doesn't have a smoke machine. 


1. Do a visual inspection of the fuel tank and cap, the carbon canister and the lines.

2. If the visual inspection reveals no obvious leaks, test the Canister Vent (CV) solenoid (mounted on the carbon canister) and the Vapor Management Valve (VMV) (located on the passenger side of the firewall).

3. The CV solenoid is normally open, and closes when energized. With key on, verify battery voltage to the Red wire at the solenoid. Then, with the solenoid connected, ground the Purple/White wire and the solenoid should close completely. If the solenoid fails to close when grounded, replace it.

4. The VMV is normally closed, and opens when energized electrically AND has vacuum to it on the small signal vacuum line. Verify good vacuum to the VMV on both the small and the large vacuum line coming from the engine. Then verify battery voltage on the Red wire with the key on. Then, with the engine running and the solenoid connected, ground the Gray/Yellow wire and check for vacuum on the 3rd port going back to the canister. If no vacuum is present, replace the VMV.

5. If all OK, monitor the Fuel Tank Pressure (FTP) sensor voltage on scan data. With no pressure or vacuum in the fuel tank, the FTP sensor voltage should be 2.4 to 2.8 volts. If OK, with the engine running, ground BOTH the CV solenoid and the VMV at the same time, and monitor the FTP sensor voltage. It should drop steadily as vacuum builds in the fuel tank, and should go to less than 1 volt. If the voltage doesn't drop, loosen the fuel cap, and if there is a hiss indicating vacuum in the tank, replace the FTP sensor. If there is no vacuum in the tank, there is a leak in the lines, tank, canister, or fuel cap. 

Potential Causes:

Malfunctioning Canister Vent (CV) Solenoid
Malfunctioning Fuel Tank Pressure (FTP) Sensor
Leaking System
Vapor Management Valve (VMV)

Tech Tips:

To avoid damage to the solenoids, do not ground either solenoid for longer than a couple of minutes at a time. 

Diagnostic Codes:



Dave Sill 

Average Reported Mileage:





Confirmed Fix Summary




Confirmed Fix

1 - 

Vapor Management Valve (VMV)




Confirmed Fix Details






Reported Fix Details

Confirmed Fix

Bob Bruno
May 21, 2008

Confirmed Fix - Exact Vehicle Match 

1997 Ford Taurus, SHO 3.4L
Vapor Management Valve (VMV)
111,000 miles

Vapor Management Valve (VMV) 




- Confirmed Fix - Exact Vehicle Match

- Confirmed Fix - Similar Vehicle Match

*- Indicates a Similar Vehicle - Not an exact match to the vehicle selected





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