Subject: Oxygen Sensor System Check Models: 911/924/924 Turbo ALL
Bulletin Number: 80 – 02
When diagnosing poor engine operation, first perform a quick-check of the Oxygen Sensor System
Work procedure:
Preliminary Conditions
- Engine in proper tune (ignition timing, idle speed etc.)
- No exhaust leaks
- Engine at operating temperature
- Connect Siemens 451 tester as follows:
- “+” lead to battery
terminal or equivalent

- “-“ lead to OXS test connection No. II (marked on the back of plug)
- “%” button on test instrument pressed in
- Tester set for four cylinders
Note
When making OXS test, do not connect any other test leads. Ignore figures in “RPM” window.
- Note readings as follows:

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