The Evaporative Emission (EVAP) control system limits the fuel vapors from escaping into the atmosphere. The EVAP transfers the fuel vapor from the sealed fuel tank to an activated carbon (charcoal) storage device (EVAP canister). The EVAP canister stores the vapors until the engine is able to use the extra fuel vapor.
When the engine is able to use the extra fuel vapor, the intake air flow purges the fuel vapor from the carbon element, and then the normal combustion process consumes the fuel vapor.
The system is required in order to detect the evaporative fuel system leaks as small as 0.040 between the fuel filler cap and the purge solenoid. The system can test the evaporative system integrity by applying a vacuum signal (ported or manifold) to the fuel tank in order to create a small vacuum.
The evaporative system includes the following components:
The evaporative leak detection diagnostic strategy is based on applying vacuum to the EVAP system and monitoring vacuum decay. The PCM monitors vacuum level via the Fuel Tank Pressure sensor input. At an appropriate time, the EVAP purge valve and the EVAP canister vent valve are turned ON, allowing engine vacuum to draw a small vacuum on the entire evaporative emission system. After the desired vacuum level has been achieved, the EVAP purge valve is turned OFF, sealing the system. A leak is detected by monitoring for a decrease in vacuum level over a given time period, all other variables remaining constant. A small leak in the system will cause DTC P0442 to be set.
A vacuum decay condition indicating a small leak is detected during the diagnostic test.
Important: Although these diagnostics are considered type A, they act like type B diagnostics under certain conditions. Whenever the EVAP diagnostics report that the system has passed, or if the battery has been disconnected, the diagnostic must fail during two consecutive cold start trips before setting a DTC. The initial failure is not reported to the diagnostic executive or displayed on a scan tool. A passing system always reports to the diagnostic executive immediately.
Check for the following conditions:
Reviewing the Fail Records vehicle mileage since the diagnostic test last failed may help determine how often the condition that caused the DTC to be set occurs. This may assist in diagnosing the condition.
Number(s) below refer to the step number(s) on the Diagnostic Table:
The powertrain OBD System Check prompts you to complete some of the basic checks and store the freeze frame and failure records data on the Scan Tool if applicable.
If a vent valve or EVAP purge valve electrical malfunction is present, the purge system will not operate correctly. Repairing the electrical malfunction that caused the additional DTC to set will very likely correct the condition that set this DTC.
Checks for a fuel tank pressure sensor stuck high condition.
Verifies that the fuel tank pressure sensor accurately reacts to EVAP system pressure changes. The EVAP station is pressurizing a sensor that normally reads vacuum. The Tech II reads high pressure at 0 volts and high vacuum at 5 volts. The Tech II can only read a max pressure of 6.0 inches of H2O (0 Volts). However the EVAP Service Station can pressurize the system to much higher pressures. The Scan Tool value should be within 0.5 in. H2O of the specified value.
Checks for a small leak in the EVAP system.
Checks for a leak in the Canister, vent line, or a leaking EVAP Vent Valve.
Checks for a leaking or stuck open EVAP canister purge valve/solenoid. The scan tool should read within 1.0 in. HG of the specified value.
The EVAP station is pressurizing a sensor that normally reads vacuum. The Tech II reads high pressure at 0 volts and high vacuum at 5 volts. The Tech II can only read a max pressure of 6.0 inches of H2O (0 Volts). However the EVAP Service station can pressurize the system to much higher pressures. The Scan Tool value should be within 0.5 in. H2O of the specified value.
Step
Action
Value(s)
Yes
No
1
Was the Powertrain OBD System Check performed?
--
Go to Step 2
Go to Powertrain On Board Diagnostic (OBD) System Check
2
Important: : Visually/physically inspect for the following conditions: • Vacuum or purge lines disconnected. Refer to Emission Hose Routing Diagram . • Loose or missing fuel fill cap.
Is DTC P1665 Evaporative Emission (EVAP) Vent Solenoid Control Circuit or DTC P1676 Evaporative Emission (EVAP) Purge Solenoid Control Circuit also set?
Go to the other DTC first
Go to Step 3
3
Is the Fuel Tank Pressure near the specified value?
0 in. H2O
Go to Step 4
Go to DTC P0453 Fuel Tank Pressure Sensor Circuit High Voltage
4
Important: : Before continuing with this diagnosis, zero the EVAP Pressure and Vacuum (inches of H2O) gauges on the J 41413 EVAP Pressure/Purge Diagnostic Station.
Important:: Do not exceed the pressure in the specified value .
5 in. H2O
Go to Step 5
Go to Step 7
5
Important: Do not exceed the pressure in the first greater specified value.
Does the EVAP Pressure decrease to less than the second lesser specified value within 2 minutes with the rotary switch in the "Off/Hold position?
15 in. H2O
10 in. H2O
Go to Step 6
Go to Diagnostic Aids
6
Can vacuum be maintained at the specified value?
5 in. Hg
Go to Step 9
Go to Step 8
7
Was a problem found?
Go to Step 15
Go to DTC P0452 Fuel Tank Pressure Sensor Circuit Low Voltage
8
Go to Step 13
9
Go to Step 10
10
Is vacuum level near the specified value?
0 in. Hg
Go to Step 12
Go to Step 11
11
Is the action complete?
12
Important: Do not exceed the 15 in. H2O pressure in the specified value.
13
14
Is action complete?
0 in H20
15
Does the EVAP pressure decrease to less than the second lesser specified value within 2 minutes with the rotary switch in the 'Off/Hold' position?
System OK
