Operation CHARM: Car repair manuals for everyone.
Home >> Porsche >> 1989 >> 928 CS V8-4957cc 5.0L >> Repair and Diagnosis >> Powertrain Management >> Computers and Control Systems >> Oxygen Sensor >> Testing and Inspection
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

Oxygen Sensor: Testing and Inspection

TESTING SENSOR VOLTAGE

Precondition: Engine at operating temperature.

1. Connect exhaust tester to the test port in the exhaust.
2. Disconnect oxygen sensor plug.




3. Connect voltmeter to terminal 1 (sensor half of plug) and ground.
4. The voltage must be in 0.1 V to 1.0 V range (depending on concentration of oxygen in exhaust).

Voltage characteristic of oxygen sensor for working temperature of 600 Degrees C.:




5. Disconnect vacuum line from fuel pressure regulator. The voltage signal must increase.

TESTING LAMBDA CONTROL FUNCTION.
1. Precondition as for the "sensor voltage" test.




2. Disconnect oxygen sensor plug. With length of cable, briefly connect terminal 1 of control-unit side of plug to ground.

The CO reading must increase.

NOTE: Do not conduct this test for any longer than required to detect a change in the CO reading of the exhaust tester.

If there is no change in the CO reading, check connection to LH control unit and LH control unit coding, if necessary, replace control unit.
pro multis · About Operation CHARM