CEL Code P1031

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07-30-2005, 09:01 AM

revhi

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CEL Code P1031

P0131 Primary Heated Oxygen Sensor (Primary HO2S) (Sensor 1) Circuit Low.

This MIL is on in my girlfriends 99 Si. Ive searched around and it seems that no one has had this code pop up in either the Civic or S2000 community. Is it just a bad sensor? The car is completley stock and has about 40k. .

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07-30-2005, 01:09 PM

Wisconsin S2k

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first try resetting the ECU.

it could be the HO2S sensor is bad. could also be a connection between the sensor and the ECU.

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07-30-2005, 01:53 PM

Slows2k

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Usually it's a bad sensor, with a biased low output voltage. You have to monitor the 02 output voltage with the engine running to verify the sensor is bad.

If the sensor input volts stay below .5 and don't rapidly change from 0-1V, the sensor is bad.

Off to Car talk as well, cuz it's for a Civic