C 1500 Truck 2WD V8-6.5L DSL Turbo VIN F (1998)
Evaporative Emissions System: Technical Service Bulletins
EVAP System - Monitor Strategy
File In Section: 06 - Engine/Propulsion System
Bulletin No.: 00-06-04-011A
Date: October, 2001
INFORMATION
Subject:
Evaporative Emissions DTC P0440, P0441, P0442, P0446
Models:
1996-2002 Passenger Cars and Trucks
With Enhanced Evaporative Emissions Engines
Except 1998-1999 Chevrolet Prizm
This bulletin is being revised to add model years and diagnostic enhancements.
Please discard Corporate Bulletin Number 00-06-04-011 (Section 6-Engine).
Enhanced Evaporative Emissions testing of 1996 and newer vehicles with enhanced evaporative emissions requires more stringent testing of the fuel
system for evaporative emissions leaks. Vehicles with this system use an on-board diagnostic module (i.e. Powertrain Control Module (PCM) or Vehicle
Control Module (VCM) as the controller. For the balance of this bulletin, we will refer to either of these components as a module.
Enhanced Evaporative Emission tests may be performed by the vehicle's module when specific conditions are met. These conditions are determined by
the calibration within the module. These calibrations are vehicle platform and engine family specific. When the key is turned to the start or run position,
the module checks the output of various sensors on the vehicle to determine when and if the Evaporative Emissions tests should be run. Refer to Engine
Controls sub-section of the appropriate Service Manual for specific DTC information.
Some of the most widely used parameters are listed below:
1.
The Barometric Pressure (BARO) is greater than a specified kPa (psi).
2.
The system voltage is between 10 and 18 volts.
3.
The intake air temperature (IAT) is within specified temperature values.
4.
The engine coolant temperature (ECT) is within specified temperature values.
5.
The ECT and IAT are within specified temperatures of each other when the vehicle engine was started.
6.
The fuel level sensor indicates the fuel level is greater than a specified % of empty and less than a specified % of full. (For a 76 L (20 gal) fuel
tank, a fuel level of more than 11 L (3 gal) but less than 64 L (17 gal) or as specified in the calibration).
7.
Some platforms such as the Alero and Grand Am, use a miles driven check as well.
For the ECT and IAT to be within the specified temperatures of each other at the time of engine start-up, the engine will have to be in the non-running
condition for a long enough period of time for the engine coolant temperature to drop from its normal operating temperature down to roughly 30°C (90°
F). This could take several hours.
When the control module determines that the above conditions are met, the module tests for a leak in the EVAP system by:
^
Electrically closing the vent valve in order to seal the system.
^
Electrically opening the purge valve which allows the running engine to draw a vacuum on the fuel tank.
^
The module then closes the purge valve, resealing the system.
^
The module then monitors the fuel tank pressure sensor and determines:
-
If vacuum was achieved.
-
If a leak is present, how large the leak is.
