Evaporative Emission Control System Diagnosis. Pontiac Firebird 1999

For 1990-2009 cars only

Makes 🢒 Pontiac 🢒 1999 🢒 Firebird 🢒 Engine 🢒 Engine Controls - 3.8L 🢒 Evaporative Emission Control System Diagnosis

EVAP Control System Overview


(1)	EVAP Vent Valve/Solenoid
(2)	EVAP Vent Valve/Solenoid Ignition Feed Circuit Terminal
(3)	EVAP Vent Valve/Solenoid Control Circuit Terminal
(4)	EVAP Vent Valve/Solenoid Filter
(5)	EVAP Vapor Lines
(6)	Fuel Tank Pressure Sensor
(7)	Fuel Tank Pressure Sensor Ground Circuit Terminal
(8)	Fuel Tank Pressure Sensor Signal Circuit Terminal
(9)	Fuel Tank Pressure Sensor Circuit 5 Volt Reference Circuit Terminal
(10)	Fuel Filler Pipe
(11)	Check Valve (Spitback)
(12)	Modular Fuel Sender Assembly
(13)	Fuel Limiter Vent Valve (FLVV)
(14)	Pressure/Vacuum Relief Valve (Optional)
(15)	EVAP Canister
(16)	EVAP Canister Purge Valve/Solenoid Ignition Feed Circuit Terminal
(17)	EVAP Canister Purge Valve/Solenoid Control Circuit Terminal
(18)	Intake Manifold Vacuum Source
(19)	EVAP Canister Purge Valve/Solenoid
(20)	EVAP Service Port

EVAP System Description

The evaporative system includes the following components:

•	The fuel tank.

•	The EVAP vent valve/solenoid.

•	The fuel tank pressure sensor.

•	The fuel pipes and hoses.

•	The fuel fill cap.

•	The EVAP vapor lines.

•	The EVAP purge lines.

•	The EVAP canister.

•	The EVAP canister purge valve/solenoid.

The EVAP purge valve/solenoid allows manifold vacuum to purge the canister. The Powertrain Control Module (PCM) supplies a Ground to energize the purge valve/solenoid (purge ON). The EVAP purge valve/solenoid control is Pulse Width Modulated (PWM) or Turned ON and OFF several times a second. The duty cycle (pulse width) is determined by engine operating conditions including load, throttle position, coolant temperature and ambient temperature. The duty cycle is calculated by the PCM and the output is commanded when the appropriate conditions have been met.

The EVAP Vent valve/solenoid is used to seal the EVAP system during diagnostic tests. The fuel tank pressure sensor is used to monitor vacuum in the system during the diagnostic tests.

A stuck closed EVAP purge valve/solenoid, Stuck open EVAP vent valve/solenoid, disconnected or damaged EVAP Purge line or vent hose, leaking fuel cap, or fill neck should set a DTC P0440. A small leak in the EVAP system should set a DTC P0442 An EVAP vent valve/solenoid stuck closed, a restricted vent hose, or a blocked EVAP canister should set a DTC P0446. A continuous purge condition with no purge commanded by the PCM (EVAP purge valve/solenoid stuck open or leaking) should set a DTC P1441. Refer to the DTC tables for further diagnostic procedures regarding the EVAP system.

Diagnostic Aids

Check for the following conditions:

•	Cracked or punctured EVAP canister.

•	Damaged or disconnected source vacuum line, EVAP purge line, vent hose or fuel tank vapor line.

•	Poor connection at the PCM.

•	Inspect harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal to wire connection.

•	Damaged harness. Inspect the wiring harness to the EVAP vent valve/solenoid, the EVAP purge valve/solenoid, and the fuel tank pressure sensor for an intermittent open or short circuit.

•	Kinked, pinched or plugged vacuum source, EVAP purge, or fuel tank vapor line. Verify that the lines are not restricted.

•	Use the following procedure to check for a carbon release condition that could plug the system.

1.	Turn off the ignition switch.

2.	Remove the EVAP canister purge valve/solenoid. Refer to Evaporative Emission Canister Purge Solenoid Valve Replacement .

3.	Lightly tap the canister purge valve on a clean work area looking for carbon particles exiting either of the vacuum ports.

4.	If no carbon release is evident, reinstall the components and continue with the DTC P0440 diagnostic table. If carbon is being released from either component, continue with this service procedure.

5.	Remove the charcoal canister from the vehicle.

Ensure that the main cylinder valve is turned off on the
Object Number: 20803 Size: SH


(1)	Main Valve
(2)	Evaporative Emission System Purge/Presure Diagnostic Station J 41413
(3)	Nitrogen Cylinder
(4)	Black Connecting Hose
(5)	Threaded Fitting
(6)	Gauge Set

EVAP purge/pressure diagnostic station.

7.	Disconnect the black hose that connects the nitrogen cylinder to the EVAP purge/pressure diagnostic station at the pressure regulator by unscrewing the knurled nut on the regulator. No tools are required to remove the black hose from the regulator.

8.	Using a section of vacuum line, connect one end over the open threaded fitting of the EVAP purge/pressure diagnostic station pressure regulator.

9.	Connect the remaining end to the purge valve end of the EVAP purge line at the vehicle and turn on the main nitrogen cylinder valve. Continue to blow any debris from the purge line for 15 seconds.

10.	Return the EVAP Pressure/Purge Diagnostic Station to its original condition by reinstalling the black hose that was disconnected in step 7.

11.	Replace the following components:

•	The EVAP canister purge valve. Refer to Evaporative Emission Canister Purge Solenoid Valve Replacement .

•	The EVAP canister. Refer to Evaporative Emission Canister Replacement EVAP Canister.

Test Description

Number(s) below refer to the step number(s) on the Diagnostic Table:

The powertrain OBD System Check promps you to complete some of the basic checks and store the freeze frame and failure records data on the Scan Tool if appplicable.

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 DTC to set will very likely correct the condition.

Checks for a fuel tank pressure sensor stuck high condition. The fuel tank pressure must be relieved by removing the canister line from the Purge Valve. The fuel fill cap will not relieve the fuel tank pressure due to a check valve in the filler neck. The check valve seals when pressure is applied to prevent vapors from escaping through the filler neck. The Scan Tool should read within +/- 1.0 in. H2O of the specified value.

Checks for a Large Leak in the EVAP system.

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 of the specified value.

Checks for a stuck closed EVAP Vent Valve/Solenoid. The value should decrease to within +/- 1.0 in Hg of the specified value.

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.

Ensures that sufficient source vacuum is present at the EVAP canister purge valve/solenoid.

Checks for a small leak in the EVAP system.

EVAP Control System Diagnosis

Step

Action

Value(s)

Yes

Was the Powertrain OBD System Check performed?

Go to Step 2

Go to the Powertrain On Board Diagnostic (OBD) System Check

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 P0443 Evaporative Emission (EVAP) Purge Solenoid Control Circuit or DTC P0449 Evaporative Emission (EVAP) Vent Solenoid Control Circuit also set?

Go to the DTC first

Go to Step 3

Ignition Switch OFF.
Remove the canister purge line from the EVAP Canister purge valve/solenoid.
Ignition Switch ON, Engine OFF.
Observe Fuel Tank Pressure on the Scan Tool.

Is the Fuel Tank Pressure near the specified value?

0 in H2O

Go to Step 4

Go to Step 9

Important: Before continuing with diagnosis, zero the EVAP Pressure and Vacuum (inches of H2O) Gauges on the J 41413 EVAP Pressure/Seal Diagnostic station.

Important: Do not exceed the pressure in the specified value.

Ignition Switch OFF.
Reconnect all EVAP hardware that was previously disconnected.
Install theJ 41415-40 Fuel Tank Cap Adapter to the fuel fill neck and fuel fill cap.
Connect the EVAP station to the fuel tank cap adaptor.
Ignition Switch ON, Engine OFF.
Capture Fail Record data for DTC P0440 and clear DTCs.
Using the scan tool, EVAP vent valve/solenoid, Command the vent valve "ON" (closed) to seal the system.
Attempt to pressurize the system to the specified value by slowly turning the EVAP Service Station rotary switch to the "pressure" position (monitor the pressure with the gauge on the cart with the rotary switch in the "Off/Hold" position).

Can specified value be achieved?

5 in. H2O

Go to Step 5

Go to DTC P0440 Evaporative Emission (EVAP) System DTC P0440 EVAP System

Maintain the Fuel Tank Pressure at the specified value (monitor the pressure with the gauge on the cart with the rotary switch in the "Off/Hold" position).
Observe fuel pressure on the scan tool.

Is the fuel tank pressure near the specified value?

5 in H2O

Go to Step 6

Go to Step 11

Command the Vent Valve/Solenoid Off (open) to relieve the pressure through the Vent Valve.

Does the EVAP pressure gauge decrease to near the second specified (lower) value within 2 minutes with the rotary switch in the "Off/Hold" position?

5 in. H2O

Go to Step 7

Go to DTC P0446 Evaporative Emission (EVAP) Vent System Performance DTC P0446 EVAP Canister Vent Blocked

Connect the in. Hg vacuum gauge on the EVAP Service Station to the purge valve/solenoid, canister side.
Ignition Switch ON, Engine OFF.
Using the scan tool, EVAP purge/seal, select the seal option to seal the EVAP system.
Start the engine and idle.
Run the engine from 1200-1500 RPM and observe vacuum level.

Is vacuum level above the specified value?

0 in. Hg

Go to Step 8

Go to Step 12

Using the scan tool, increase purge to 100%.
Run the engine from 1200-1500 RPM and observe vacuum level.

Is vacuum level above the specified value?

15 in. Hg

Go to Step 14

Go to Step 13

Ignition Switch OFF.
Remove the EVAP Canister line from the fuel tank or EVAP canister.
Ignition Switch ON, Engine OFF.
Observe Fuel Tank Pressure on the Scan Tool.

Is the Fuel Tank Pressure near the specified value?

0 in H2O

Go to Step 10

Go to DTC P0453 Fuel Tank Pressure Sensor Circuit High Voltage

Check for a kinked or restricted canister purge line between the EVAP canister purge valve and EVAP canister.
Repair the canister purge line as necessary.

Is action complete?

0 in. H2O

Go to Step 14

Visually/Physically inspect for the following conditions:

•	Restricted fuel tank vapor line.

•	Restricted EVAP purge line.

If a problem is found, repair as necessary.

Was a problem found?

Go to Step 14

Go to DTC P0452 Fuel Tank Pressure Sensor Circuit Low Voltage

Check for no source vacuum to thr EVAP purge valve.
If problem was found repair as necessary.

Was a problem found?

Go to Step 14

Important: Check for carbon release into the EVAP system. Refer to diagnostic Aids.

Locate and repair cause of no source vacuum to the EVAP purge valve.

Is the action complete?

Go to Step 14

Go to Step 12

Important:: Do not exceed the pressure in the specified value.

Reconnect all EVAP hardware that was previously disconnected.
Ignition Switch On, Engine OFF.
Using scan tool, purge/seal, select the seal option to seal the EVAP system.
Pressurize the system to the first specified (higher) value by slowly turning the EVAP Service station rotary switch to the "pressure" position (monitor the pressure with the gauge on the cart with the rotary switch in the "Off/Hold" position).

Does the EVAP pressure decrease to less than the second specified (lower) value within 2 minutes with the rotary switch in the "OFF/Hold" position?

15 in H2O

10 in H2O

Go to DTC P0442 Evaporative Emission (EVAP) System Small Leak Detected

System OK