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For 1990-2009 cars only
Makes 🢒 Pontiac 🢒 2008 🢒 Torrent 🢒 Diagnostic Navigation 🢒 Vehicle Diagnostic Information 🢒 Restricted Exhaust

Typical Data
Object Number: 1886217 Size: SH

Diagnostic Aids

Caution: While engine is operating, the exhaust system will become extremely hot. To prevent burns avoid contacting a hot exhaust system.

Important: If the vehicle is equipped with a diesel engine do not perform this diagnostic. The exhaust system does not have a location for installing the J 35314-A Exhaust Back Pressure Gage. Instead remove the suspect component, operate the vehicle and verify for improved performance. If performance is improved, then replace the faulty component.

Test Description

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

  1. Certain exhaust restrictions are not present during idle or low load conditions. This step will isolate to a restricted exhaust that is present during high engine load conditions.

    During high engine load, the 02 sensor(s) voltage will cross count several times upon initial load, then climb high and stay high.

    During high engine load, the 02 sensors voltage will continue to cross count from high to low voltage.

    2.

  2. 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 .

    Removing the heated oxygen sensor (HO2S) may set a DTC. When finishing this diagnostic table, be sure to clear all codes.

  3. 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.

Restricted Exhaust

Step

Action

Value(s)

Yes

No

1

Did you verify the customers complaint?

--

Go to Step 2

--

2

Are any DTCs present?

--

Go to Diagnostic Trouble Code (DTC) List - Vehicle

Go to Step 3

3

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

--

Go to Step 4

Go to Symptoms - Engine Exhaust

4

Does the engine start?

--

Go to Step 6

Go to Step 5

5

Were you sent here from Engine Cranks but Does Not Run diagnostic chart?

--

Go to Step 7

Go to Engine Cranks But Does Not Run for the 3.4L engine or Engine Cranks But Does Not Run for the 2.8, 3.0, 3.2, 3.6L engine

6

Is the condition present at idle/park?

--

Go to Step 9

Go to Step 8

7

Caution: Refer to Hot Exhaust System Caution in the Preface section.

  1. Remove the pre-catalyst heated oxygen sensor (HO2S).
  2. Attempt to start the engine.

Does the engine start?

--

Go to Step 11

Go to Engine Cranks But Does Not Run for the 3.4L engine or Engine Cranks But Does Not Run for the 2.8, 3.0, 3.2, 3.6L engine

8

  1. Road test the vehicle.
  2. Install a scan tool.
  3. Take a snapshot of the condition using the appropriate data stream that will include:
    4. • Engine load
    • Throttle angle (actual)
    • Pre-catalyst oxygen sensors
  4. Plot out the engine data using graph to lay over all 3 readings.
    5. • Single exhaust will be Eng load/tp angle/HO2S 1
    • Dual exhaust will be Eng load/HO2S S 1/HO2S S2
    • Refer to the graph above for Typical normal/abnormal readings.

Is the O2 sensor voltage spiking?

--

Go to Step 11

Go to Symptoms - Engine Controls for the 3.4L engine or Symptoms - Engine Controls for the 2.8, 3.0, 3.2, 3.6L engine

9

Caution: Refer to Hot Exhaust System Caution in the Preface section.

  1. Remove the pre-catalyst heated oxygen sensor (HO2S).
  2. Install the J 35314-A in place of the HO2S sensor.
  3. Start and run the engine.
  4. Increase and monitor the engine speed at 2,500 RPM.
  5. Observe the exhaust system back pressure reading on the gage.

Does the reading exceed the specified value?

27.6 kPa (4 psi)

Go to Step 10

Go to Step 8

10
  1. Turn the engine OFF and place the ignition in the LOCK position.
  2. Remove the J 35314-A .
  3. Install the pre-catalyst HO2S sensor.
  4. Remove the post-catalyst HO2S sensor.
  5. Install the J 35314-A in place of the post HO2S sensor.
  6. Start the engine.
  7. Increase and monitor the engine speed at 2,500 RPM.
  8. Observe the exhaust system back pressure reading on the gage.

Does the reading exceed the specified value?

27.6 kPa (4 psi)

Go to Step 11

Go to Step 8

11

Inspect the exhaust system for the following conditions:

    • Damage in the exhaust pipe
    • Debris in the exhaust pipe
    • Muffler or resonator internal failure

Did you find and correct the condition?

--

Go to Step 14

Go to Step 12

12

Replace the catalytic converter.

Did you find and correct the condition?

--

Go to Step 14

Go to Engine Cranks But Does Not Run for the 3.4L engine or Engine Cranks But Does Not Run for the 2.8, 3.0, 3.2, 3.6L engine

13
  1. Remove the J 35314-A .
  2. Install the post-catalyst HO2S sensor.

Did you correct the condition?

--

System OK

Go to Symptoms - Engine Controls for the 3.4L engine or Symptoms - Engine Controls for the 2.8, 3.0, 3.2, 3.6L engine

14

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

Did you correct the condition?

--

System OK

Go to Symptoms - Engine Controls for the 3.4L engine or Symptoms - Engine Controls for the 2.8, 3.0, 3.2, 3.6L engine