Emissions System - EVAP System Diagnostic Flow Charts: Overview
XT303-03X-TYPE
DATE:
05/02
MODEL:
2002 MY-ON X-TYPE
VIN:
C00001-ON
Evaporative System - Diagnostic Flow Charts
Issue:
This bulletin provides information on diagnosing the evaporative system of 2002 MY-ON X-TYPE vehicles.
EVAPORATIVE SYSTEM - TABLE OF CONTENTS
^ A brief summary of leak check.
^ A quick overview of how the evaporative system diagnostic operates.
^ Leak test profile (Illustration 1).
This is a diagram of the fuel tank pressure sensor profile when the system is operating correctly. It is used as a reference in the leak check summary.
^ Evaporative leak check Diagnostic Trouble Codes (DTC) index. An explanation of each DTC.
^ Flowchart for each DTC flagged by the evaporative system diagnostic shown.
^ Drive cycles.
To enable the technician to be confident that he is driving the vehicle in the correct way to allow the drive cycle to operate.
^ Generic Connector Inspection.
^ Generic Harness Check.
Note:
All three leak detection DTCs (P0442, P0455 and P0456) are logged as temporary codes when a leak is detected on the first trip within a leak check. If the fault re-occurs and is detected on a second leak check (second trip) the relevant fault code is then logged as a permanent DTC. When diagnosing faults with the evaporative system, the permanent code is the code, which needs to be investigated.
LEAK CHECK BRIEF SUMMARY
Background
This diagnostic is designed to determine the presence of a leak in the fuel vapor system.
There are two elements to this diagnostic, 0.040 in and 0.020 in tests; these are executed during normal vehicle operation. The 0.040 in test will operate when the vehicle is in motion, the 0.020 in test runs when the vehicle returns to rest. Both tests operate in a similar manner; the major difference is the level of depression pulled during the test cycle. Figure 1, shows a typical fuel tank pressure profile during a leak test.
At the point that the test initializes A1, the evaporative (purge) valve beg ins to close. A2 the Canister Close Valve (CCV) closes. The vapor system is now sealed (assuming that there is not a leak present).
The pressure in the fuel tank will now begin to increase (the amount of increase is dependant upon the amount and type of fuel, the temperature, and if a leak is present) until B.
It is over this section that the system determines if the evaporative (purge) valve is unable to fully close (P0443).
At B, the evaporative (purge) Valve begins to open; a depression is now produced in the fuel tank due to engine vacuum. The tank pressure is pulled down to -2 Kpa (-20 mBar) for the 0.040 in test and -1.25 Kpa (-12.5 mBar) for the 0.020 in test.
The rate that this pull down occurs is dependant upon the presence of a leak, if the target pressure cannot be achieved in the prescribed time then the system judges there to be a 'gross leak' (P0455- note this code is also used to indicate evaporative (purge) valve stuck closed and CCV stuck open).
When the target pressure is achieved, the evaporative (purge) valve re-closes C (again, the system is now sealed). A setting period now ensues and the system determines if it is necessary to perform a second pull down (this does not always occur).
The pressure in the tank now begins to increase (again it is dependent upon the amount and type of fuel, the temperature, and the presence of a leak). A leak at this stage will have a significant effect on the rate of pressure rise.
At D, the CCV re-opens and the remaining pressure in the tank is lost, the tank pressure will return close to atmospheric pressure before purge re-initializes E. It is the time taken for this pressure to return to or close to atmospheric pressure, that determines if there is a restriction in the atmospheric port (vent port) of the vapor system (P0446).
The ECM now performs a calculation using various elements of the test cycle and determines the presence and relative size of a leak. If a leak is present, the relative P codes will be flagged accordingly.
Leak Check Flowchart P - 1.b
P0443 Evaporative Purge Valve Leaking.
Method 1 Manual
Leak Check Flowchart P - 1.b
P0443 Evaporative Purge Valve Leaking
Method 2 - Using a Vacuum Pump
Leak Check Flowchart P - 1.c
P0444/P0445 Evaporative Purge Valve
Leak Check Flowchart P - 1.d
P0446 Evaporative CCV
Leak Check Flowchart P - 1.e
P0447/P0448 Evaporative CCV
Leak Check Flowchart P - 1.f
P0450 Fuel Tank Pressure Sensor Malfunction
Leak Check Flowchart P - 1.g
P0452/P0453 Fuel Tank Pressure Sensor
Flow Chart P - 1.h
P0455 Gross Leak
DRIVE CYCLE FOR "GREEN" ECM
To Enable ECM to Relearn Fuel Metering Adaptations
This procedure should be performed whenever the vehicle battery has been disconnected. Due to component tolerance and wear during the normal running of a vehicle, fuel metering and air requirements for an engine will vary over time. The ECM has the ability to adjust for this variation by learning the level of compensation that is required. These compensation values are referred to as adaptations.
If the vehicle battery is disconnected, all adaptations held within the ECM will be lost (i.e. set to zero); the ECM is then referred to as "Green". To enable the engine to run correctly and for the evaporative purge system to function, the ECM must "relearn" these adaptations. There a four areas or sites that need to be relearned.
This guide is intended to assist with the process of re-adapting the ECM without the need for any additional equipment, e.g. WDS unit.
Green ECM drive cycle.
1. Idle vehicle until fully warm. Coolant temperature gauge just below mid point (48/50%).
2. Leave idling for a further 3 minutes minimum. (Site 1)
3. Drive the vehicle, with the air conditioning off, on level road using a constant throttle (use speed control if fitted) for at least 60 seconds, in the following gears, at the stated engine speeds for sites 1, 2, 3 and 4 in table 1 shown.
4. Return to rest and leave the vehicle idling for 60 seconds.
If sufficient adaptations have occurred, the evaporative purge valve should now be operating. This can be verified manually by either touching or listening to the valve. It is possible to feel the evaporative purge valve switching by touching the valve
WARNING:
THE EVAPORATIVE PURGE VALVE IS LIKELY TO BE HOT.
To listen to the valve, for possible switching, use a stethoscope or other suitable instrument (switching frequency is 10 Hz).