Operation CHARM: Car repair manuals for everyone.
Home >> Porsche >> 1994 >> 928 GTS V8-5397cc 5.4L DOHC >> Repair and Diagnosis >> Powertrain Management >> Computers and Control Systems >> Testing and Inspection >> Component Tests and General Diagnostics
Manuals through 2025 now available!

Our trusted friends have launched a new website named LEMON, which has newer manuals. It also contains all the CHARM manuals.

LEMON is the spiritual successor to CHARM, I recommend you try it!

Link: lemon-manuals.la or lemon-manuals.org.ua

(Some people have issue connecting. LEMON is investigating. For now, use Firefox or change your DNS server)

Or, hide this message: temporarily or permanently

Component Tests and General Diagnostics

NOTE: Do not conduct this test any longer than needed to detect a change in CO (carbon monoxide) reading on analyzer.


1. Be sure engine is at normal operating temperature.
2. Connect exhaust gas analyzer to sampling points in exhaust pipe.

Oxygen Sensor Plug:





3. Disconnect oxygen sensor plug.

Fig. 49 Oxygen Sensor Connector Plug:





4. Using a jumper wire, momentarily connect terminal 1 of control unit side of plug, to ground.
5. CO reading should increase.
6. If there is no change, check connection to LH control unit and unit coding. If needed, replace control unit.
pro multis · About Operation CHARM