GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Pontiac 🢒 2009 🢒 Vibe - FWD 🢒 Engine 🢒 Engine Exhaust 🢒 Restricted Exhaust

Diagnostic Aids

For dual exhaust systems a quick check of exhaust flow will help determine which side of the exhaust system is restricted. The side that has less exhaust flow is the side that will be suspect, and diagnosis should begin there.

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 J 35314-A Exhaust Back Pressure Gage.

    Removing the secondary air injection (AIR) check valve or heated oxygen sensor (HO2S) may set a DTC. When finishing this diagnostic table, be sure to clear all codes.

  2. If high back pressure is not found at idle, increasing the engine speed may help find a restriction.

    Perform operational check before returning vehicle to customer.

    3.

  3. This step will isolate the catalytic converter from the remainder of the exhaust system.

    4.

  4. Confirming that the condition has been fixed is essential. If the symptom still exists and the vehicle has a dual exhaust system, proceed to step 2 and repeat diagnostic procedure on the opposite exhaust pipe.

Step

Action

Value(s)

Yes

No

1

Did you verify the customer complaint?

--

Go to Step 2

--

2

Did you review the exhaust symptoms diagnostic information and perform the necessary inspections?

--

Go to Step 3

Go to Symptoms - Engine Exhaust

3

Is the system equipped with dual exhaust?

--

Go to Diagnostic Aids

Go to Step 4

4

  1. Remove the pre-converter heated oxygen sensor (HO2S) that isnearest exhaust manifold. .
  2. Install the J 35314-A Exhaust Back Pressure Gage in place of the HO2S sensor.
  3. Start and run the vehicle.
  4. With the engine idling at normal operating temperature, record the exhaust system back pressure reading on the gage.

Does the reading exceed the specified value?

8.6 kPa (1.25 psi)

Go to Step 6

Go to Step 5

5

  1. With the J 35314-A still installed, increase and monitor engine speed to 2,000 RPM.
  2. Observe the exhaust system back pressure reading on the gage.

Does the reading exceed the specified value?

8.6 kPa (1.25 psi)

Go to Step 7

System OK

6

  1. Turn the ignition OFF and place the ignition in the lock position.
  2. Loosen the exhaust manifold to catalytic converter flange bolts.
  3. Start the vehicle.
  4. With the engine idling at normal operating temperature, record the exhaust system back pressure reading on the gage.

Does the reading exceed the specified value?

8.6 kPa (1.25 psi)

Go to Step 9

Go to Step 7

7
  1. Turn the engine OFF and place the ignition in the lock position.
  2. Remove the J 35314-A .
  3. Re-install the pre-converter HO2S sensor.
  4. On all engines, remove the post-catalyst HO2S sensor.
  5. Install the J 35314-A in place of the post HO2S sensor.
  6. Start and idle the engine and monitor the engine speed to 2,000 RPM.
  7. Observe the exhaust system back pressure reading on the gage.

Does the reading exceed the specified value?

8.6 kPa (1.25 psi)

Go to Step 8

Go to Step 10

8

Inspect the exhaust system for the following conditions:

    • Damage in the exhaust pipe
    • Debris in the exhaust pipe
    • Muffler internal failure
    • 2-layer exhaust pipe separation

Did you find and correct the condition?

--

Go to Step 11

--

9

Replace the catalytic converter assembly.

Did you find and correct the condition?

--

Go to Step 12

--

10

Replace the catalytic converter.

Did you find and correct the condition?

--

Go to Step 12

--

11

Remove the J 35314-A and reinstall the HO2S sensor.

Did you correct the condition?

--

Go to Step 12

Go to Step 2

12

  1. Clear any codes.
  2. Road test the vehicle in order to verify the repair.

Did you correct the condition?

--

System OK

Go to Step 2