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Home >> Pontiac >> 2008 >> Torrent GXP, AWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 106 (Engine Exhaust System) >> Diagnostic Information and Procedures >> Restricted Exhaust >> Test Description

Test Description

WARNING: This page is about a different car, the 2009 Pontiac Torrent and 2009 Chevrolet Equinox. However, it is still accessible from the selected car via links, so may be relevant.

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

  1. 8:  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. 9:  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. See Special Tools .
  3. 14:  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
WARNING: Refer to Hot Exhaust System Warning .
  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:
    • Engine load
    • Throttle angle (actual)
    • Pre-catalyst oxygen sensors
  4. Plot out the engine data using graph to lay over all 3 readings.
    • 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 
WARNING: Refer to Hot Exhaust System Warning .
  1. Remove the pre-catalyst heated oxygen sensor (HO2S).
  2. Install the J 35314-A  in place of the HO2S sensor. See Special Tools .
  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  . See Special Tools .
  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. See Special Tools .
  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  . See Special Tools .
  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
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