Test Description
The numbers below refer to the step numbers on the diagnostic table.
- 4: 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 AIR check valve or HO2S sensor may set a DTC. When finishing this diagnostic table, be sure to clear all codes. See «Special Tools»(ref-277937-S41695491722008012100000) .
- 5: This step will isolate the catalytic converter from the remainder of the exhaust system.
- 8: 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 customers 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 vehicle equipped with a 6.6L diesel engine? | Go to Diagnostic Aids | Go to Step 4 | |
| 4 | Remove the AIR check valve or the heated oxygen sensor (HO2S) that is in front of and closest to the catalytic converter. Refer to Heated Oxygen Sensor Replacement - Bank 1 Sensor 1 or Heated Oxygen Sensor Replacement - Bank 2 Sensor 1 for the 4.3L engine, Heated Oxygen Sensor Replacement - Bank 1 Sensor 1 or Heated Oxygen Sensor Replacement - Bank 2 Sensor 1 for the 4.8L, 5.3L, and 6.0L engine, Heated Oxygen Sensor Replacement - Bank 1 Sensor 1 or Heated Oxygen Sensor Replacement - Bank 2 Sensor 1 for the 8.1L engine. Install the J 35314-A Exhaust Back Pressure Gage in place of the AIR check valve or HO2S sensor. See Special Tools . Start the engine. Increase and monitor the engine speed at 2,000 RPM. Observe the exhaust system back pressure reading on the gage. Does the reading exceed the specified value? | 20 kPa (3 psi) If equipped with a 4.8L, 5.3L, or 6.0L - 3.4 kPa (0.5 psi) | Go to Step 5 | Go to Step 8 |
| 5 | Turn the engine off and place the ignition in the lock position. Remove the J 35314-A . See Special Tools . Re-install the AIR check valve/HO2S sensor. Refer to Heated Oxygen Sensor Replacement - Bank 1 Sensor 1 or Heated Oxygen Sensor Replacement - Bank 2 Sensor 1 for the 4.3L engine, Heated Oxygen Sensor Replacement - Bank 1 Sensor 1 or Heated Oxygen Sensor Replacement - Bank 2 Sensor 1 for the 4.8L, 5.3L, and 6.0L engine, Heated Oxygen Sensor Replacement - Bank 1 Sensor 1 or Heated Oxygen Sensor Replacement - Bank 2 Sensor 1 for the 8.1L engine. Remove the post-catalyst HO2S sensor. Refer to Heated Oxygen Sensor Replacement - Bank 1 Sensor 2 or Heated Oxygen Sensor Replacement - Bank 2 Sensor 2 for the 4.3L engine, Heated Oxygen Sensor Replacement - Bank 1 Sensor 2 or Heated Oxygen Sensor Replacement - Bank 2 Sensor 2 for the 4.8L, 5.3L, and 6.0L engine, Heated Oxygen Sensor Replacement - Bank 1 Sensor 2 or Heated Oxygen Sensor Replacement - Bank 2 Sensor 2 for the 8.1L engine. Install the J 35314-A in place of the post HO2S sensor. See Special Tools . Start the engine. Increase and monitor the engine speed at 2,000 RPM. Observe the exhaust system back pressure reading on the gage. Does the reading exceed the specified value? | 20 kPa (3 psi) If equipped with a 4.8L, 5.3L, or 6.0L - 3.4 kPa (0.5 psi) | Go to Step 6 | Go to Step 7 |
| 6 | Inspect the exhaust system for the following conditions: Damage in the exhaust pipe Debris in the exhaust pipe Muffler or resonator internal failure Two-layer exhaust pipe separation Did you find and correct the condition? | Go to Step 8 | ||
| 7 | Replace the catalytic converter. Refer to Catalytic Converter Replacement (4.3L, 4.8L, and 5.3L Engines) or Catalytic Converter Replacement (6.0L and 8.1L Engines) or Catalytic Converter Replacement (6.6L Engine) . Did you find and correct the condition? | Go to Step 8 | ||
| 8 | Remove the J 35314-A . See Special Tools . Reinstall the AIR check valve or the HO2S sensor. Refer to Heated Oxygen Sensor Replacement - Bank 1 Sensor 2 or Heated Oxygen Sensor Replacement - Bank 2 Sensor 2 for the 4.3L engine, Heated Oxygen Sensor Replacement - Bank 1 Sensor 2 or Heated Oxygen Sensor Replacement - Bank 2 Sensor 2 for the 4.8L, 5.3L, and 6.0L engine, Heated Oxygen Sensor Replacement - Bank 1 Sensor 2 or Heated Oxygen Sensor Replacement - Bank 2 Sensor 2 for the 8.1L engine. Clear any codes. Road test the vehicle in order to verify the repair. Did you correct the condition? | System OK | Go to Step 2 |
Restricted Exhaust
Exhaust System Description
| IMPORTANT | Use of non-OEM parts may cause driveability concerns. |
The exhaust system carries exhaust gases, treated by the catalytic converter, through a resonator, if applicable and into the exhaust muffler where exhaust noise is lessened.
In order to secure the exhaust pipe to the exhaust manifold, a flange and seal-joint coupling is utilized. The exhaust system may utilize a slip-joint coupling design with a clamp and a U-bolt or a flange connection with a gasket.
Exhaust hangers and rubber insulators help to support the weight of the exhaust pipe along with insulating any exhaust system vibration, rattle, or noise.
Exhaust hangers also space the exhaust system away from the underbody of the vehicle and allows the exhaust system to expand as the exhaust system warms up.
Exhaust heat shields are used to protect the body and other components from damage due to the heat from the exhaust system.
The exhaust system may be comprised of the following components
- Exhaust manifold
- Exhaust pipes
- Catalytic converters
- Exhaust muffler
- Exhaust resonator, if equipped
- Exhaust tail pipe, if equipped
- Exhaust hangers
- Exhaust heat shields