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 . See «Special Tools»(ref-268155-S06779030852007101800000) . Removing the AIR check valve or HO2S sensor may set a DTC. When finishing this diagnostic table, be sure to clear all codes.
- 5: 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.
- 6: This step will isolate the catalytic converter from the remainder of the exhaust system.
- 9: 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 system equipped with dual exhaust? | Go to Diagnostic Aids | Go to Step 4 | |
| 4 | Remove the AIR check valve or the HO2S that is in front of and closest to the catalytic converter. Install the J 35314-A in place of the AIR check valve or HO2S sensor. See Special Tools . Start and run the vehicle. With the engine idling at normal operating temperature, record the exhaust system back pressure reading on the gauge. Does the reading exceed the specified value? | 8.6 kPa (1.25 psi) | Go to Step 6 | Go to Step 5 |
| 5 | With the J 35314-A still installed increase and monitor engine speed to 2000 RPM. See Special Tools . Observe the exhaust system back pressure reading on the gage. Does the reading exceed the specified value? | 20.7 kPa (3 psi) | Go to Step 6 | Go to Step 9 |
| 6 | 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. Remove the post-catalyst HO2S sensor. Install the J 35314-A in place of the post HO2S sensor. See Special Tools . Start and idle the engine and monitor the engine speed to 2000 RPM. Observe the exhaust system back pressure reading on the gauge. Does the reading exceed the specified value? | 20.7 kPa (3 psi) | Go to Step 7 | Go to Step 8 |
| 7 | 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 9 | ||
| 8 | Replace the catalytic converter. Refer to Catalytic Converter Replacement (4.2L Engine) or Catalytic Converter Replacement (5.3L Engine) . Did you find and correct the condition? | Go to Step 9 | ||
| 9 | Remove the J 35314-A and reinstall the AIR check valve or the HO2S sensor. See Special Tools . 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