Test Description
The numbers below refer to the step numbers on the diagnostic table.
- 3: 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. See «Special Tools»(ref-241745-S23849998972006081100000) . Removing the heated oxygen sensor (HO2S) may set a DTC. When finishing this diagnostic table, be sure to clear all codes.
- 4: This step will isolate the catalytic converter from the remainder of the exhaust system.
| Step | Action | Values | 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 | CAUTION: Refer to HOT EXHAUST SYSTEM CAUTION in Cautions and Notices. Remove the pre-catalyst heated oxygen sensor (HO2S). Refer to Heated Oxygen Sensor Replacement - Position 1 in Engine Controls - 3.5L (LX9). Install the J 35314-A Exhaust Back Pressure Gage in place of the HO2S sensor. See Special Tools . Start and run the vehicle. Increase and monitor the engine speed at 2,500 RPM. Observe the exhaust system back pressure reading on the gage. Does the reading exceed the specified value? | 9 kPa (1.25 psi) | Go to Step 4 | Go to Step 7 |
| 4 | Turn the engine OFF and place the ignition in the LOCK position. Remove the J 35314-A . See Special Tools . Install the pre-catalyst HO2S sensor. Refer to Heated Oxygen Sensor Replacement - Position 1 in Engine Controls - 3.5L (LX9). Remove the post-catalyst HO2S sensor. Refer to Heated Oxygen Sensor Replacement - Position 2 in Engine Controls - 3.5L (LX9). 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 2,500 RPM. Observe the exhaust system back pressure reading on the gage. Does the reading exceed the specified value? | 9 kPa (1.25 psi) | Go to Step 5 | Go to Step 6 |
| 5 | 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 7 | ||
| 6 | Replace the catalytic converter. Refer to Catalytic Converter Replacement . Did you find and correct the condition? | Go to Step 7 | ||
| 7 | Remove the J 35314-A . See Special Tools . Install the post-catalyst HO2S sensor. Refer to Heated Oxygen Sensor Replacement - Position 2 in Engine Controls - 3.5L (LX9). Clear any codes. Road test the vehicle in order to verify the repair. Did you correct the condition? | System OK | Go to Step 2 |
| CAUTION |
|---|
| Refer to HOT EXHAUST SYSTEM CAUTION in Cautions and Notices. |
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