For 1990-2009 cars

### System Description

Proper diagnosis for a restricted exhaust system is essential before any components are replaced. Using the Restricted Exhaust System Check table should determine if the exhaust system is restricted. The best place for checking the exhaust system is at the O2S 1 location. Once the test is completed, coat threads with anti-seize compound P/N 5613695 or equivalent prior to O2S re-installation.

### Test Description

Number(s) below refer to the step number(s) on the Diagnostic Table.

1. The OBD System Check prompts the technician to complete some basic checks and store the freeze frame and failure records data on the scan tool if applicable. This creates an electronic copy of the data taken when the fault occurred. The information is then stored in the scan tool for later reference.

2. The exhaust system under normal conditions has very low back pressure. If the exhaust system is restricted, a noticeable increase in exhaust pressure is noticed on the gage.

3. If no high back pressure is found at idle, increasing the engine speed to 3000 RPM may find a slight restriction. The added engine speed increases the exhaust flow which will help determine if there is a slight restriction.

#### Restricted Exhaust System Check

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
1 | Was the Powertrain On-Board Diagnostic (OBD) System Check performed? | -- | Go to Step 2 | Go to Powertrain On Board Diagnostic (OBD) System Check
2 |

1. Carefully remove the O2S 1 from the exhaust manifold.
2. Install the exhaust back pressure tester J 35314-A in place of the O2S 1.

Is the action complete?

--

Go to Step 3

--

3 |

1. Turn the ignition switch ON, with the engine running.
2. With the engine idling in park or neutral, observe the exhaust system back pressure reading on the gage. The reading should not exceed the specified value.

Does the reading exceed the specified value?

3.4 kPa (0.5 psi)

Go to Step 5

Go to Step 4

4 | Increase the engine speed to 3000 RPM and observe back pressure reading on the gage. The reading should not exceed the specified value. Does the reading exceed the specified value? | 5 kPa (0.75 psi) | Go to Step 5 | Go to Step 7
5 |

1. Check the entire exhaust system for a collapsed pipe, heat distress, or possible internal muffler failure.
2. Replace any component found malfunctioning.

Did any component require replacement?

--

Go to Step 7

Go to Step 6

6 | Replace the catalytic converter. Is the action complete? | -- | Go to Step 7 | --
7 |

1. Allow engine to idle until normal operating temperature is reached.
2. Check if any DTCs are set.

Are any DTCs displayed that have not been diagnosed?

--

Go to the applicable DTC table

System OK