GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 1998 🢒 Chevy Suburban 4WD - RHD 🢒 Engine 🢒 Engine Controls - 5.0L and 5.7L 🢒 Evaporative Emission Control System Diagnosis

Object Number: 196163 Size: MF
EVAP/PCV - Comp Loc Figure
Engine Controls Schematics
OBD II Symbol Description Notice
Handling ESD Sensitive Parts Notice

Circuit Description

The Enhanced evaporative system includes the following components:

    • The fuel tank
    • The EVAP vent solenoid
    • The fuel tank pressure sensor
    • The fuel pipes and hoses
    • The vapor lines
    • The fuel cap
    • The evaporative emission canister
    • The purge lines
    • The EVAP purge solenoid

The evaporative leak detection diagnostic strategy is based on applying the vacuum to the EVAP system and monitoring the vacuum decay. The VCM monitors the vacuum level via the fuel tank vacuum sensor input. At an appropriate time, the EVAP purge solenoid and the EVAP vent solenoid turn ON, allowing the engine vacuum to draw a small vacuum on the entire evaporative emission system. If a sufficient vacuum level cannot be achieved, a large leak or a malfunctioning EVAP purge solenoid is indicated. The following conditions can cause this problem:

    • A missing, malfunctioning, improperly installed, or loose fuel cap
    • A disconnected or malfunctioning fuel tank pressure sensor
    • A disconnected, damaged, pinched, or blocked EVAP purge line
    • A disconnected or damaged EVAP vent hose
    • A disconnected, damaged, pinched, or blocked fuel tank vapor line
    • A disconnected or malfunctioning EVAP purge solenoid
    • A disconnected or malfunctioning EVAP vent solenoid
    • An open ignition feed circuit to the EVAP vent or purge solenoid
    • A damaged EVAP canister
    • A leaking fuel sender assembly O-ring
    • A leaking fuel tank or fuel filler neck

Results of Incorrect Operation
    • Poor idle, stalling and poor driveability can be caused by:
       - Damaged canister
       - Hoses split, cracked, or not connected to the proper tubes
    • Evidence of fuel loss or fuel vapor odor can be caused by:
       - Liquid fuel leaking from the fuel lines
       - Cracked or damaged EVAP canister
       - Disconnected, misrouted, kinked, deteriorated or damaged EVAP pipe or canister hoses
       - Air cleaner or air cleaner gasket improperly seated

Test Description

The numbers below refer to the step numbers on the diagnostic table.

  1. This step checks the fuel tank pressure sensor at atmospheric pressure.

    2.

  2. This step determines if the EVAP system has a restriction or leak.

    3.

  3. This step determines if there is a restriction in the Fuel Tank Vapor Line or Canister.

    4.

  4. This step checks for a restriction in the EVAP Canister.

Step

Action

Value(s)

Yes

No

1

Important: Before clearing the DTCs, use the scan tool in order to record the Freeze Frame and the Failure Records for reference. This data will be lost when the Clear DTC Information function is used.

Was the Powertrain On-Board Diagnostic (OBD) System Check performed?

--

Go to Step 2

Go to Powertrain On Board Diagnostic (OBD) System Check

2

Is DTC P0446, P0452, or P0453 set?

--

Go to applicable DTC table

Go to Step 3

3

  1. Turn OFF the ignition.
  2. Install a scan tool.
  3. Remove the fuel cap.
  4. Turn ON the ignition.
  5. Observe the Fuel Tank Pressure on the scan tool.

Is the Fuel Tank Pressure at the specified value?

-1-1 in.H2O

Go to Step 4

Go to Fuel Tank Pressure Sensor Diagnosis

4

Important: Before continuing with the diagnosis, zero the EVAP Pressure and Vacuum gauges on the Enhanced EVAP Pressure Purge Diagnostic Cart J 41413. Refer to the tool operating instructions.

Important: Make sure the fuel cap is secured properly. A poorly installed or loose fuel cap can cause DTC P0440.

  1. Install the fuel cap
  2. Connect the Enhanced EVAP Pressure Purge Diagnostic Cart J 41413 to the EVAP service port.
  3. Using the scan tool, command the EVAP vent valve ON (Closed).
  4. Attempt to pressurize the EVAP system using the Cart.
  5. Monitor pressure using gauge on Cart for 2 minutes.

Can the specified value be obtained and held?

5 in.H2O

Go to Step 5

Go to Step 6

5

  1. Maintain fuel tank pressure at 5 inches of H2O (Turn the rotary switch on the cart to the HOLD position).
  2. Observe the Fuel Tank Pressure on the scan tool.

Is the Fuel Tank Pressure within the specified value?

3-7 in.H2O

Go to Step 9

Go to Step 8

6
  1. Disconnect the Fuel Tank Vapor Line and the EVAP Purge Line from the EVAP Canister.
  2. Block the canister fitting for the Fuel Tank Vapor Line.
  3. Connect a hand vacuum pump to the canister fitting for the EVAP Purge Line.
  4. Ensure that the EVAP Vent Valve is still commanded ON (Closed).
  5. Attempt to apply vacuum to the EVAP canister.

Can the specified value of vacuum be obtained and held?

5 in.Hg

Go to Step 12

Go to Step 7

7
  1. Leave system connected as in step 6.
  2. Disconnect the Vent hose at the Vent Valve.
  3. Plug end of the Vent hose.
  4. Using the hand vacuum pump apply vacuum up to the specified value.

Can the specified value of vacuum be obtained and held?

5 in.Hg

Go to Step 17

Go to Step 11

8

  1. Disconnect Fuel Tank Vapor Line from the Canister.
  2. Attempt to pressurize the EVAP system using the Enhanced EVAP Pressure Purge Diagnostic Cart J 41413.
  3. Monitor pressure using gauge on cart.

Can the specified value of pressure be obtained and held?

5 in.H2O

Go to Step 18

Go to Step 15

9
  1. Disconnect Purge Line at the Canister.
  2. Connect the in. Hg vacuum gauge on the Enhanced EVAP Pressure Purge Diagnostic Cart J 41413 to the Purge Line.
  3. Start engine
  4. Command EVAP Purge Solenoid Valve to 100%.

Is the vacuum gauge at or above the specified value?

12 in.Hg

Go to Diagnostic Aids

Go to Step 10

10
  1. Disconnect Purge Line from the Purge Solenoid Valve.
  2. Connect the in. Hg vacuum gauge on the Enhanced EVAP Pressure Purge Diagnostic Cart J 41413 to the Purge Solenoid Valve.
  3. Start engine
  4. Command EVAP Purge Solenoid Valve to 100%.

Is the vacuum gauge at or above the specified value?

12 in.Hg

Go to Step 14

Go to Step 16

11

Check the Vent hose for possible cause of vacuum leak and repair as necessary.

Was a repair necessary?

--

Go to Step 19

Go to Step 18

12
  1. Check for the following:
    2. • Missing or faulty fuel cap.
    • Disconnected or leaking fuel Tank Vapor Line.
    • Disconnected or damaged EVAP Purge Line.
  2. If a problem is found, repair as necessary.

Was a problem found?

--

Go to Step 19

Go to Step 13

13

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

  1. Using the scan tool, command the EVAP Vent Valve ON.
  2. With the Enhanced EVAP Pressure Purge Diagnostic Cart J 41413 connected to the EVAP service port continuously attempt to pressurize the EVAP system by leaving the cart control knob in the pressurize position.
  3. Using the Enhanced EVAP Ultrasonic Leak Detector J 41416, locate the leak in the EVAP system. It may be necessary to partially lower the fuel tank in order to examine the connections on the top of the fuel tank . Refer to Diagnostic Aids.
  4. Repair the leak in the EVAP system.

Is the action complete?

15 in. H2O

Go to Step 19

--

14

Repair restriction in EVAP Purge Line.

Is action complete?

--

Go to Step 19

--

15

Repair restriction in Fuel Tank Vapor Line.

Is action complete?

--

Go to Step 19

--

16

Replace the EVAP Purge Solenoid Valve. Refer to Diagnostic Aids. Refer to EVAP Canister Purge Solenoid Valve Replacement in Repair Instructions.

Is the action complete?

--

Go to Step 19

--

17

Replace the EVAP Vent Valve. Refer to Diagnostic Aids. Refer to EVAP Vent Valve Replacement (EVAP) in Repair Instructions.

Is the action complete?

--

Go to Step 19

--

18

Replace EVAP Canister. Refer to Evaporative Emission Canister Replacement in Repair Instructions.

Is the action complete?

--

Go to Step 19

--

19

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

  1. Turn the ignition ON leaving the engine OFF.
  2. Using the scan tool, command the EVAP Vent Valve ON (Closed).
  3. Pressurize the EVAP system to the first specified value using the Enhanced EVAP Pressure Purge Diagnostic Cart J 41413 (monitor pressure using the gauge on the cart).
  4. Turn the rotary switch on the cart to the HOLD position and observe the EVAP pressure gauge.

Does the pressure decrease to less than the second specified value within 2 minutes?

15 in. H2O

10 in. H2O

Go to Step 2

Go to Step 20

20
  1. Use the scan tool in order to select the DTC and the Clear DTC Information functions.
  2. Perform the Service Bay Test for EVAP.

Was the test performed and passed?

--

Go to Step 21

Go to Step 2

21

Use the scan tool in order to display the Capture Info and the Review Capture Info functions.

Are there any DTCs displayed that have not been diagnosed?

--

Go to applicable DTC table

System OK