Contour Enthusiasts Group Archives Forums General Troubleshooting Code P0446

To start I have a 1998 SVT with 56k miles, totally stock. I have had the CEL light on for over a month after I disconnected the battery and reset the PCM after having the CEL light stay on the first time. The CEL stayed off for about 500 miles and 4 days and then returned. I have no noticable drivabilty problems and no drop in mileage.

Yesterday I had a mechanic friend with a Snap-on Engine Tester read my codes. One of the items the tester showed after running an diagnostic routine was the following:

'TSB 97-19-6 DTC P0446 Reprogram PCM.' This was not stored in memory but showed up after the diagnostic test.

Any idea what the the P0446 code means? Also I can't find the mentioned TSB.

Eric

P0446 = Evaporative Emission Control System Vent Control malfunction.

For TSB's http://www.alldata.com

From my 1996 service manual.
P0446 Evaporative emission control system Canister Vent (CV) solenoid control malfunction #2 in the list below.

Evaporative Emission (EVAP) Running Loss System Monitor

The Evaporative Emission (EVAP) Running Loss System Monitor is an on-board strategy designed to detect a leak from a hole (opening) equal to or greater than 1.016 mm (0.040 inch) in the EVAP Running Loss system. The proper function of the individual components of the EVAP Running Loss system as well as its ability to flow fuel vapor to the engine is also examined. The EVAP Running Loss System Monitor relies on the individual components of the EVAP Running Loss system to apply vacuum to the fuel tank and then seal the entire EVAP Running Loss system from atmosphere. The fuel tank pressure is then monitored to determine the total vacuum lost (bleed-up) for a calibrated period of time. Inputs from the engine coolant temperature (ECT) sensor, intake air temperature (IAT) sensor, mass air flow (MAF) sensor, vehicle speed sensor (VSS), fuel level input (FLI) and fuel tank pressure (FTP) sensor are required to enable the EVAP Running Loss System Monitor.

NOTE:
During the EVAP Running Loss System Monitor Repair Verification Drive Cycle a PCM reset with key on, engine off will bypass the minimum soak time required to complete the monitor. The EVAP Running Loss System Monitor will not run if the key is turned off after a PCM reset. The EVAP Running Loss System Monitor will not run if a MAF sensor failure is indicated. The EVAP Running Loss System Monitor will not initiate until the Heated Oxygen Sensor (HO2S) Monitor has completed.


The EVAP Running Loss System Monitor is executed by the individual components of the EVAP Running Loss system as follows:

1. The function of the EVAP canister purge valve is to create a vacuum on the fuel tank. A minimum duty cycle on the EVAP canister purge valve (75%) must be met before the EVAP Running Loss System Monitor can begin.

2. The canister vent (CV) solenoid will close (100% duty cycle) with the EVAP canister purge valve at its minimum duty cycle to seal the EVAP Running Loss system from atmosphere and obtain a target vacuum on the fuel tank.

3. The fuel tank pressure (FTP) sensor will be used by the EVAP Running Loss System Monitor to determine if the target vacuum on the fuel tank is being reached to perform the leak check. Once the target vacuum on the fuel tank is achieved, the change in fuel tank vacuum for a calibrated period of time will determine if a leak exists.

4. If the initial target vacuum cannot be reached, DTC P0455 (large leak or no purge detected) will be set. The EVAP Running Loss System Monitor will abort and not continue with the leak check portion of the test.

If the initial target vacuum is exceeded, a system flow fault exists and DTC P1450 (unable to bleed-up fuel tank vacuum) is set. The EVAP Running Loss System Monitor will abort and not continue with the leak check portion of the test.

If the target vacuum is obtained on the fuel tank, the change in the fuel tank vacuum (bleed-up) will be calculated for a calibrated period of time. The calculated change in fuel tank vacuum will be compared to a calibrated threshold for a leak from a hole (opening) of 1.016 mm (0.040 inch) in the EVAP Running Loss system. If the calculated bleed-up is less than the calibrated threshold, the EVAP Running Loss system passes. If the calculated bleed-up exceeds the calibrated threshold, the test will abort and rerun the test up to three times.

If the bleed-up threshold is still being exceeded after three tests, a vapor generation check must be performed before DTC P0442 (small leak detected) will be set. This is accomplished by returning the EVAP Running Loss system to atmospheric pressure by closing the EVAP canister purge valve and opening the CV solenoid. Once the FTP sensor observes the fuel tank is at atmospheric pressure, the CV solenoid closes and seals the EVAP Running Loss system.

The fuel tank pressure build-up for a calibrated period of time will be compared to a calibrated threshold for pressure build-up due to vapor generation.

If the fuel tank pressure build-up exceeds the threshold, the leak test results are invalid due to vapor generation. The EVAP Running Loss System Monitor will pass and complete.

If the fuel tank pressure build-up does not exceed the threshold, the leak test results are valid and DTC P0442 will be set.

5. The malfunction indicator lamp (MIL) is activated for DTCs P0442, P0455 and P1450 (or P446) after two occurrences of the same fault. The MIL can also be activated for any EVAP Running Loss system component DTCs in the same manner. The EVAP Running Loss system component DTCs P0443, P0452, P0453 and P1451 are tested as part of the Comprehensive Component Monitor (CCM).

I appreciate the response. Now does anyone know why the phrase 'Reprogram PCM' was included after the P0446 code?

Eric

Here is exactly what happened.

When the scanning tool was first plugged in it read the following stored codes:

P0420 Bank 1 cat efficiency low
P1151 HO2S21 sensor indicator lean

We then erased those codes and ran the diagnostic routine. We ran some tests with the key on and engine off and then with the key on and engine on, all prompted by the tester. With the engine on the tester ran the engine up off idle then down told us to turn the steering wheel and pump the brakes. I can't remember the exact order. At the end of all of this the following was shown on the tester:

TSB 97-25A Test information
TSB 97-19-6 DTC P0446 Reprogram PCM
TSB List P0442 P0445

Right now, after about 125 miles and 3 days the CEL has not come on. The engine continues to run fine and mpg has not dropped.

If the P0420 or P1151 return I know what to do. But I don't know what to do about the other test results. ANy ideas.

Eric

Well if your cel comes back change your O2 sensor.

It sounds as though Ford has reprogramed your PCM with a new code that covers a TSB for DTC 442, 445 & 446.
To check, see if Ford was nice enough to put a new label on your computer, or call Ford with your VIN number
and see if they have a record of it being re-flashed.

I'm guessing here, but that's my .02

The indicated TSB does not apply to the Contour therefore the TSB reference should be ignored. See the PCED for the Contour for proper diagnostics to resolve the DTC.

See below for text of TSB-19-6:


/////

FORD:
1997 CROWN VICTORIA

LINCOLN-MERCURY:
1997 GRAND MARQUIS, MARK VIII, TOWN CAR

LIGHT TRUCK:
1997 ECONOLINE, EXPLORER

This TSB article is being republished in its entirety to add calibrations.

CALIBRATION:
7-18E-R06, 7-18F-R06, 7-18H-R06, 7-18I-R10, 7-18J-R06, 7-18M-R06, 7-18N-R06, 7-18Q-R06, 7-18S-R06, 7-38K-R07, 7-38L-R07, 7-54G-R10, 7-57B-R05, 7-57R-R05, 7-58B-R05, 7-58C-R06, 7-58V-R06, 7-74U-R06, 7-74V-R06, 7-96T-R06

WARNING:
THIS MODIFICATION IS AUTHORIZED ONLY FOR THE LISTED ENGINE. PERFORMING THIS MODIFICATION ON OTHER ENGINE CALIBRATIONS IS UNAUTHORIZED AND COULD CREATE LIABILITY UNDER APPLICABLE FEDERAL OR LOCAL LAWS.

ISSUE:
The Malfunction Indicator Lamp (MIL) may illuminate and Diagnostic Trouble Code (DTC) P0446 may be stored in memory. This may be caused by On-Board Diagnostics II (OBD II) performing checks when conditions are not ideal.

ACTION:
Perform normal diagnostics as outlined in the Powertrain Control/Emissions Diagnosis (PC/ED) Service Manual and reprogram the Powertrain Control Module (PCM). Refer to the following PCM Application Chart for correct PCM Calibration.
/////

Steve

Many thaks for the TSB info. Just one questions, what does PCED mean?

Eric