GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Isuzu 🢒 1999 🢒 S/T Isuzu - 4WD 🢒 Engine 🢒 Engine Controls - 2.2L 🢒 Evaporative Emission Control System Diagnosis

Object Number: 387281 Size: LF
Engine Controls Components
Cell 20: Oxygen Sensors
OBD II Symbol Description Notice
Powertrain Control Module Connector End Views
Handling ESD Sensitive Parts Notice
Handling ESD Sensitive Parts Notice

Circuit Description

Applying a vacuum to the EVAP system and monitoring for a vacuum decay checks the evaporative emission system. The Control Module monitors the vacuum level through the fuel tank vacuum sensor signal. At an appropriate time, the EVAP canister purge valve and the EVAP vent solenoid turn ON, allowing the engine to draw a small vacuum on the entire evaporative emission system. After the desired vacuum level has been achieved, the EVAP canister purge valve turns OFF, sealing the system. A leak is detected by monitoring for a decrease in the vacuum level over a given time period, when all other variables remain constant. A leak, a blockage, or a malfunctioning component in the system causes a DTC to set.

Diagnostic Aids

Check for the following conditions:

    • Poor connection at the Control Module. Inspect the harness connectors for the following conditions:
       - Backed out terminals
       - Improper mating
       - Broken locks
       - Improperly formed or damaged terminals
       - Poor terminal to wire connections.
    • A damaged harness. Inspect the wiring harness for damage. If the harness appears to be OK, observe the Fuel Tank Vacuum display on the scan tool while moving connectors and wiring harnesses related to the sensor. A change in the display will indicate the location of the fault.
    • An incorrect purge or vacuum source line routing. Verify that the source vacuum and purge lines to the EVAP canister purge valve are not switched.

Refer to Evaporative Emission System Cleaning before starting repairs.

Evaporative Emission System Check

Step

Action

Value(s)

Yes

No

1

Did you perform the Powertrain On-Board Diagnostic (OBD) System Check?

--

Go to Step 2

Go to Powertrain On Board Diagnostic (OBD) System Check

2
  1. Turn ON the ignition switch leaving the engine OFF.
  2. Install a scan tool.

Is DTC P0452, P0453, P0461, P0462, or P0463 also set?

--

Go to DTC Diagnostic tables first

Go to Step 3

3
  1. Command the EVAP canister purge valve ON and OFF with the scan tool.
  2. Command the vent solenoid ON and OFF with the scan tool.

Does the purge vale and the vent solenoid click when commanded ON and OFF?

--

Go to Step 4

Go to

Powertrain Control Module Outputs Diagnosis

4
  1. Remove the fuel cap.
  2. Observe the Fuel Tank Pressure value on the scan tool.

Is the Fuel Tank Pressure within the specified values?

-2.4 to 2.4 mmHg

(-1.28 to 1.28 in. H2O)

Go to Step 5

Go to

DTC P0452 Fuel Tank Pressure Sensor Circuit Low Voltage

or

DTC P0453 Fuel Tank Pressure Sensor Circuit High Voltage

5

Important:: Before continuing with diagnosis, zero the EVAP Pressure and Vacuum gauges on the J 41413 EVAP pressure/purge Diagnostic Station (refer to tool operating instructions).

  1. Reinstall the fuel cap.
  2. Command the EVAP vent solenoid ON (Closed) with the scan tool.
  3. Connect the EVAP pressure/purge Diagnostic Station to the EVAP service port.

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

  4. Pressurize the EVAP system to the first specified value using the EVAP pressure/purge Diagnostic Station (monitor the pressure by using the gauge on the cart).
  5. Observe the Fuel Tank Pressure value on the scan tool.

Is the Fuel Tank Pressure at the second specified value?

7.2 - 16.8 mmHg

(3.85 - 8.99 in. H2O)

Go to Step 6

Go to

DTC P0452 Fuel Tank Pressure Sensor Circuit Low Voltage

or

DTC P0453 Fuel Tank Pressure Sensor Circuit High Voltage

6

Observe the EVAP system Pressure on the EVAP pressure/purge Diagnostic Station while commanding the vent solenoid OFF (Open) with the scan tool.

Does the EVAP system pressure decrease to the specified value within 5 seconds?

0 mmHg (0 in. H2O)

Go to Step 7

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

7
  1. Start the engine.
  2. Remove the fuel cap.
  3. Use the scan tools EVAP SEAL SYSTEM function to seal the EVAP system.
  4. Replace the fuel cap.
  5. Raise the engine RPMs to the specified value.
  6. Monitor the Fuel Tank Pressure value on the scan tool for at least 5 seconds.

Is the Fuel Tank Pressure value decreasing?

1,500 RPM

Go to DTC P1441 Evaporative Emission (EVAP) System Flow During Non-Purge

Go to Step 8

8
  1. Command the EVAP vent solenoid ON (closed) and the EVAP canister purge valve ON (100%) with the scan tool.
  2. Raise the engine RPMs to the specified value.
  3. Monitor the Fuel Tank Pressure value on the scan tool for at least 5 seconds.

Is the Fuel Tank Pressure value decreasing?

1,500 RPM

System OK

Go to DTC P0440 Evaporative Emission (EVAP) System