GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2000 🢒 Alero Export 🢒 Engine 🢒 Engine Controls - 2.4L 🢒 Restricted Exhaust System Check

System Description

Proper diagnosis for a restricted exhaust system is essential before any components are replaced. Using the Restricted Exhaust System Check table should determine if the exhaust system is restricted. The best place for testing the exhaust system is at the oxygen sensor (O2S 1) location. Once the test is completed, coat threads with anti-seize compound P/N 5613695 or equivalent prior to O2S re-installation.

Test Description

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

  1. The exhaust system has very low back pressure under normal conditions . If the exhaust system is restricted, a significant increase in the exhaust pressure is noticed on the gauge.

    2.

  2. If high back pressure is not found at idle, increasing the engine speed to 3,000 RPM may help find a slight restriction. The added engine speed will increases the exhaust flow.

    3.

  3. This step will isolate the catalyst convertor from the remainder of the exhaust system.

    4.

  4. If the muffler is plugged, inspect the catalytic convertor to determine if the internal material has broken apart.

Restricted Exhaust 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

    Caution: Avoid contact with moving parts and hot surfaces while working around a running engine in order to prevent physical injury.

  1. Carefully remove the O2S 1 from the exhaust manifold. Refer to Oxygen Sensor Replacement .
  2. Install a J 35314-A exhaust back pressure tester or equivalent in place of the O2S 1.
  3. Start and idle the engine in Park or in Neutral.
  4. Observe the exhaust system back pressure reading on the gauge.

Does the back pressure exceed the specified value?

3.4 kPa (0.5 psi)

Go to Step 4

Go to Step 3

3
  1. Increase the engine speed to 3,000 RPM .
  2. Observe the back pressure reading on the gauge.

Does the back pressure exceed the specified value?

5 kPa (0.75 psi)

Go to Step 4

Go to Step 8

4
  1. Turn off the ignition.

    2. Caution: Avoid contact with moving parts and hot surfaces while working around a running engine in order to prevent physical injury.

  2. Disconnect and remove the exhaust back pressure tester.
  3. Reinstall the O2S 1. Refer to Oxygen Sensor Replacement .
  4. Remove the HO2S 2. Refer to Heated Oxygen Sensor Replacement .
  5. Install the exhaust back pressure tester in place of the HO2S 2.
  6. Start the engine and Idle the engine in Park or in Neutral.
  7. Observe the exhaust system back pressure reading on the gauge.

Does the back pressure exceed the specified value?

3.4 kPa (0.5 psi)

Go to Step 6

Go to Step 5

5
  1. Increase the engine speed to 3,000 RPM .
  2. Observe the back pressure reading on the gauge.

Does the back pressure exceed the specified value?

5 kPa (0.75 psi)

Go to Step 6

Go to Step 7

6
  1. Turn off the ignition.

    2. Caution: Avoid contact with moving parts and hot surfaces while working around a running engine in order to prevent physical injury.

  2. Inspect the entire exhaust system for the following conditions:
    3. • Any collapsed pipes
    • Any heat distress
    • An internal muffler malfunction
  3. If a problem is found, repair as necessary.

Did you find and correct the condition?

--

Go to Step 8

Go to Step 7

7

Caution: Avoid contact with moving parts and hot surfaces while working around a running engine in order to prevent physical injury.

Replace the catalytic converter. Refer to Catalytic Converter Replacement in Exhaust Systems.

Did you complete the repair?

--

Go to Step 8

--

8

    Caution: Avoid contact with moving parts and hot surfaces while working around a running engine in order to prevent physical injury.

  1. Remove the exhaust back pressure gauge.
  2. Reinstall the O2S 1 if the sensor is still removed. Refer to Oxygen Sensor Replacement .
  3. Reinstall the HO2S 2 if the sensor is still removed. Refer to Heated Oxygen Sensor Replacement .
  4. Start and idle the engine until a normal operating temperature is reached.
  5. Use a scan tool in order to determine if any DTCs are set.

Are any DTCs set?

--

Go to Diagnostic Trouble Code (DTC) List/Type

System OK