O2 Sensor

I had the check engine light on my 97 blazer. The dealer checked the codes and said I have 2 busted O2 sensors. Before I could have them changed the lights came on once after coming out from the dealer and disappeared ever since. Its been 15 days and no check engine lights. Should I go and have those sensors changed or wait till they come on again? Are the sensors border line bad? Please advice!

Did they give you the codes? O2s dont just break.

No the codes were not revealed. I shall keep that in mind, I think the next time I get a check engine light I will buy the code reader may pay off in the long run. So do you advice me to ignore the GM advice and wait for the warning light again? Does the computer report a warning and if not heeded or reset stop reporting it?:confused:

I drive a 96 Blazer. I had to get two 02 sensors replaced. My check engine light would come on every so often, but disappear, never to be seen for weeks at a time, sometimes. I had the dealer replace the 02 sensors for me. They cost $130 a piece. So you might want to look into doing it yourself, and only buying the 02 sensors. But yes, I have had the same problem before.

Take a look at this situation first, might explain why it is intermitent. Unless it comes back on I wouldn't worry about it just yet.

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ENGINE ROUGH, MISS & OXYGEN SENSOR DTCS #77-65-12 - (03/13/1997)
SUBJECT: ENGINE ROUGH, MISS, AND OXYGEN SENSOR DTCS (REPLACE OXYGEN SENSOR JUMPER HARNESS)

MODELS: 1996-97 CHEVROLET AND GMC S/T TRUCKS 1996-97 OLDSMOBILE BRAVADA 1997 ISUZU WITH 4.3L V6 ENGINES (VINS W, X - RPOS L35, LF6)

CONDITION:

SOME OWNERS MAY COMMENT ABOUT AN ENGINE MISS AND/OR ROUGHNESS AND A SES LIGHT.

CAUSE:

SOME OXYGEN SENSORS ON THE PASSENGER SIDE OF THE VEHICLE HAVE BEEN FOUND TO BE DAMAGED DUE TO WATER INTRUSION. APPROXIMATELY 20% OF THE OXYGEN SENSORS RETURNED FOR ANALYSIS ON THESE MODELS HAVE EXHIBITED THIS CONDITION. IF ANY OXYGEN SENSOR RELATED DTC IS STORED, MOISTURE MAY HAVE ENTERED THE JUMPER HARNESS THAT CONNECTS THE THREE PASSENGER SIDE OXYGEN SENSORS TO THE MAIN ENGINE HARNESS AND DAMAGE THE SENSOR AND THE HARNESS. OXYGEN SENSORS THAT HAVE BEEN DAMAGED BY WATER WILL HAVE CORROSION ON ONE OR MORE OF THE SENSORS (4) TERMINALS. THE JUMPER HARNESS CONNECTOR AT THE SAME LOCATION MAY OR MAY NOT SHOW SIMILAR CORROSION. IF THERE IS UNDETECTED MOISTURE IN THE JUMPER HARNESS, A REPLACEMENT OXYGEN SENSOR CAN BE DAMAGED RESULTING IN A REPEAT FAILURE. IN ADDITION, A REPLACEMENT OXYGEN SENSOR MAY BE MISDIAGNOSED AS FAULTY WHEN THE ACTUAL FAULT IS UNDETECTED MOISTURE IN THE JUMPER HARNESS.

CORRECTION:

1. FOLLOW THE STRATEGY BASED DIAGNOSTICS AND PUBLISHED PROCEDURES FOR THE SPECIFIC SYMPTOM AND DTC. 2. INSPECT THE OXYGEN SENSOR CONNECTORS FOR SIGNS OF MOISTURE OR "BLUISH-GREEN" CORROSION ON THE CONTACTS AND IN THE CONNECTOR CAVITIES. 3. IF WATER INTRUSION IS SUSPECTED, BUT NO CORROSION IS EVIDENT, SENSOR FUNCTION MAY BE CHECKED USING A DVOM TO MEASURE RESISTANCE ACROSS THE SENSOR'S PURPLE AND TAN CONTACTS. A DEFECTIVE SENSOR WILL SHOW A RESISTANCE VALUE. A GOOD SENSOR WILL SHOW NO CONTINUITY (INFINITE RESISTANCE) OR "OPEN". 4. IF THESE SIGNS ARE DETECTED, REPLACE THE OXYGEN SENSOR JUMPER HARNESS AND ALL AFFECTED OXYGEN SENSOR(S). DO NOT ATTEMPT TO REPAIR THE JUMPER HARNESS BY CLEANING OR REPLACEMENT OF CORRODED TERMINALS. DO NOT USE OR APPLY ANY TYPE OF SEALANT ANYWHERE IN THE OXYGEN SENSOR CONNECTORS OR WIRES. REPAIR ATTEMPTS TO OXYGEN SENSOR HARNESSES GENERALLY RESULT IN A REPEAT FAILURE. 5. RECORD ALL DTCS ENCOUNTERED DURING PROBLEM DIAGNOSIS ON THE REPAIR ORDER. THIS IS NEEDED FOR ENGINEERING ANALYSIS OF THE COMPONENTS. 6. VERIFY THE SYMPTOM AND/OR DTC IS CORRECTED BEFORE RETURNING THE VEHICLE TO THE OWNER.

IMPORTANT
THE NEW JUMPER HARNESS MUST BE ROUTED ACCORDING TO THE COMPONENT LOCATION VIEWS IN SECTION 8A OF THE APPROPRIATE S/T TRUCK SERVICE MANUAL.

PARTS INFORMATION

PART NUMBER DESCRIPTION QUANTITY 12173753 OXYGEN SENSOR WIRING HARNESS, 2WD 1 12173754 OXYGEN SENSOR WIRING HARNESS, 4WD 1