Fault handling I, catalyst damaging misfiring

If catalyst damaging misfiring occurs, the driver is warned immediately by the CHECK ENGINE lamp flashing at 1 Hz, irrespective of whether the lamp was already on or not. A diagnostic trouble code will be generated at the same time.

For the CHECK ENGINE lamp to go out without any other measures being taken requires 3 consecutive driving cycles under similar operating conditions as when the fault first occurred without the catalyst damaging misfiring returning.

For the diagnostic trouble code to be cleared requires a further 40 fault-free warming-up cycles.

1. Fault criteria for catalyst damaging misfiring fulfilled
   Fig 1: Diagnostic Flow Chart - Catalyst Damaging Misfiring

   Courtesy of SAAB-SCANIA OF AMERICA, INC.

   Dependents are OK

2. CHECK ENGINE lamp flashing at 1 Hz, diagnostic trouble code generated
3. Catalyst damaging misfiring ceases
4. Diagnostic trouble code cleared
5. CHECK ENGINE lamp goes on continuously
   Fig 2: Diagnostic Flow Chart - Catalyst Damaging Misfiring

   Courtesy of SAAB-SCANIA OF AMERICA, INC.
6. Catalyst damaging misfiring does not occur for 40 warming-up cycles
7. Catalyst damaging misfiring does not occur for 3 consecutive driving cycles under similar operating conditions as when the fault first occurred and CHECK ENGINE lamp goes out.