Notes on Troubleshooting

Notes On Troubleshooting

Working on the oxygen sensors

NOTE: Oxygen sensors used with the DME 7.8







The LSU (Lambda sensor Universal) is able to determine the lambda value in a wide range window

The LSF (Lambda sensor Flat) is only able to determine lambdas greater or less than 1 (the rich/lean jump)







Arrangement of oxygen sensors for 996 Turbo







Arrangement of oxygen sensors for 996 aspirated engine

NOTE:
- Do not interchange oxygen sensors before and after the catalytic converter, otherwise implausible error entries will arise. This information refers to the possibility of installing a sensor before the cat in the installation position of a sensor after the cat in the exhaust line. The plugs themselves are coded and cannot be interchanged.
- Do not use contact spray on the plug connections of the oxygen sensor, otherwise irreparable damage will be caused to the lines (contamination of the oxygen sensor via the reference air duct).

Troubleshooting procedure
Troubleshooting can only be performed when the fault is present. In other words, specific troubleshooting can only be performed in accordance with instructions (given under Diagnosis/troubleshooting for each fault code) if the entry has the status 'present' in the fault memory.

If the fault is currently 'not present', please check the following:
- Is the fault correction counter and perhaps the deletion counter decremented? This would provide information on a remedied fault (however achieved).
- Is the fault an old one? Read out the extended fault memory (operating time and mileage at last fault entry)
- Are the diagnostic conditions satisfied? If necessary, perform a short test or test drive
- Are officially approved plug connections and ground points of the affected current path OK?
- Set all wiring harnesses of the affected current path to a state that corresponds to driving by pulling and shaking them (loose contact)
- Condition/gas tightness of catalytic converter
- For the tank system: Condition/gas tightness of hoses and the tank cap, if applicable