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(248-2506) Supplementary fault diagnosis, catalytic converter, T7 and T8

Symptom: - Engine jerk, weak engine - Flashing CHECK ENGINE lamp - Diagnostic trouble codes for misfiring, damaging catalytic converter

TECHNICAL SERVICE BULLETIN
Bulletin Nbr: 248-2506
Date: ........... November 2004
Market: ej US/CA
Supplementary fault diagnosis, catalytic converter, T7 and T8

Cars affected

Saab 9-5 (9660) M98- with Trionic 7 engine management system

Saab 9-3 (9400) M98-03 with Trionic 7 engine management system

Saab 9-3 (9440) M03- with Trionic 8 engine management system

Background

There are certain engine faults that may result in reducing the efficiency of the catalytic converter. If a large quantity of unburned fuel reaches a hot catalytic converter in a short time, it is possible for extreme temperatures to develop within the catalyst. These extreme temperatures may damage the cell structure of the catalytic converter. This damage can result in heightened exhaust back pressure.

There are many types of conditions that may generate the diagnostic trouble code for poor catalytic converter function. Sometimes multiple trips or other specific conditions must occur before the diagnostic trouble code is registered. This may result in a vehicle in the workshop with a developing problem that has not yet registered a diagnostic trouble code.

If there is any uncertainty in such cases over the function of the catalytic converter, a new function in Tech2 can supplement the OBD system by enabling an alternative diagnosis of the catalytic converter in the workshop. The Tech2 diagnosis does not replace the on-board diagnosis in the control module and should be viewed only as a complement to assure a proper diagnosis. This Tech2 diagnosis is designed to detect seriously damaged converters.

In certain markets there is no oxygen sensor 2 on T7 M98-99. The test shall nevertheless make and evaluation of the exhaust system back pressure.

This bulletin can be used if catalytic converter damage is suspected.

Possible primary faults:

- No spark on one or more cylinders

- Incorrect fuel mixture (e.g. when running the tank dry)

Symptom description

- Engine jerk, weak engine

- Flashing CHECK ENGINE lamp

- Diagnostic trouble codes for misfiring, damaging catalytic converter



Procedure

Note

Tech2, version 114.000 or later is required to carry out this work. All known primary faults must be remedied and diagnostic trouble codes cleared.



1. Connect Tech2. Select "Quick check of catalytic converter" under the "Miscellaneous" menu in the engine management system. Follow the instructions. The testing starts automatically as soon as the coolant temperature exceeds 60ºC.

Note

It is vital that the accelerator pedal is kept still and that the engine speed is even during the testing. This is particularly important during the part when Tech2 indicates that it is collecting the values from oxygen sensor 2. If the above instructions are not followed then the testing can give incorrect results.


2. Tech2 carries out back pressure measurement by evaluating the values from the mass air flow sensor and the manifold absolute pressure sensor. If either of these is faulty then the result can also be misleading.

The result of the testing will be one of the following:

• Catalytic converter OK

• Low ability to absorb oxygen

• High back pressure

3. If the ability to absorb oxygen is low: replace catalytic converter.

In the event of high back pressure: ensure that the fault is not further back in the exhaust system. If not, replace catalytic converter.


Warranty/Time Information

In the case of customer complaint and if the car is within the warranty period , use the following information to fill out the claim:

Failed Object: 25451

Fault/Reason code: X

Location code: 09

Repair/Action code: 08

Time: 0.1 hr