1992 Isuzu Truck Ohms resistance of Oxygen Sensor circuit

CARIUS QUESMAN

MEMBER
1992 ISUZU TRUCK

Computer problem
1992 Isuzu Truck 4 cyl Two Wheel Drive Manual

Is it normal for the Oxygen Sensor circuit thru the ECM computer to have 391,000 ohms resistance?

I've already checked the wire going to the ECM, and it only has about 1 ohm resistance, but the resistance of the wire AND it's path thru the ECM back to ground is 391,000 ohms. Is that kinda high for an O2 circuit?

1 Reply

RASMATAZ

MECHANIC
75,992 POSTS

TESTING THE OXYGEN (O2) SENSOR

CAUTION:DO NOT attempt to measure O2 sensor output voltage with a conventional voltmeter. Current drain of voltmeter could damage sensor. O2 sensor voltage signal can be measured using a 10-megohm (minimum input impedance) digital voltmeter. For further information, see appropriate TESTS W/CODES article in the ENGINE PERFORMANCE Section.

Start engine, and warm to operating temperature. Ensure vehicle is operating in closed loop. Unplug O2 sensor connector at sensor.
Using Digital Volt-Ohmmeter (DVOM) with a minimum 10-megohm input impedance, connect DVOM (on voltmeter scale) between ground and O2 sensor connector (sensor side).
Place a short jumper wire in sensor lead (computer side). While holding jumper wire in one hand, alternately touch negative battery terminal and then positive terminal with other hand. DO NOT touch sensor lead directly to battery.
Monitor DVOM reading. When negative battery terminal is touched, O2 sensor output voltage should increase (up to one volt). When positive battery terminal is touched, O2 sensor output voltage should drop (as low as.1 volt). If O2 sensor does not respond as indicated, replace sensor.