Cummins/Onan — Testing the Oxygen Sensor
Testing & diagnosis · Oxygen sensor (floorcare engines)
From a Cummins/Onan service manual covering: P216, P218, P220, P248. Check it applies to your exact model before use.
Applies to: Cummins/Onan P216, Cummins/Onan P218, Cummins/Onan P220, Cummins/Onan P248
Before you start
- If the emissions warning light comes on and the engine shuts down, emissions of deadly carbon monoxide gas could be excessive. See Troubleshooting and repair the engine as necessary.
Procedure
- Measure DC voltage between the Ground (white) and O2 Out (black) leads of the oxygen sensor while the engine is running.
- If voltage ranges between 0.3 and 0.7 VDC, the O2 sensor does not need to be replaced.
- If voltage is consistently high, the engine is running rich.
- If there is no voltage, check all connections first, then replace the O2 sensor if necessary.
Tools required
- DC voltmeter Amazon
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- Oxygen sensor voltage 0.3 to 0.7 VDC
Full service-parts list: Cummins/Onan P216 →, Cummins/Onan P218 →, Cummins/Onan P220 →, Cummins/Onan P248 →
Source: Cummins/Onan service manual. Steps and values are as documented; always cross-check against the official manual and any later revisions for your exact serial number before servicing.