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Express & G-Series Vans Offered in both a full size van, or a large box truck, the Express is the modern GM workhorse

Chevrolet Express
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  #1  
Old 02-23-2010, 07:37 PM
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Default P0300 Misfire Code Chevy Express Van

Have replaced one or more 02 Sensors, Cleared code and code returned. Van will drive fine sometimes and sometimes it will run really rough. Concerned about the 02 sensors, One or more 02 Sensor read between 18 & 20 and the others read 700 or better. Is this normal? Trying to get a good understanding of how to read these on this vehicle. Van has been to the dealership no luck. Any idea what we can try to solve this problem?
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Old 02-27-2010, 08:13 AM
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Default Same Code on Atro

AA I'm working on the same code on an Astro Van page. I replaced two of the three O2 sensors with out improvement. With the van at temperature I disconnect the O2 and measured open resistance on the signal wires (Blue and White). Replaced the sensors and read about 20 ohmo on each sensor at temperature. On the Astro, the right front and rear sensors read open when cold.

What is your method for O2 troubleshooting, OBD ii or other.
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Old 02-27-2010, 09:34 AM
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check plugs, wires, cap, rotor, fuel filter, fuel pressure. P0300 wouldn't necessarily be caused by an O2 sensor. it would be more ignition or fuel delivery
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Old 02-27-2010, 09:51 AM
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the O2 sensor reads the exhaust, however it comes out, and tells ecm how to compensate, add or subtract gas. if your ignition system isn't up to par, you will get funny readings as the sensor(s) are trying to tell the ecm what it reads. fouled or worn plugs, bad wires and such will not burn the air/fuel mixture properly, thus your exhaust gas will not come out at an optimum, which will cause sensor to read funny as it tries to help adjust. make sure all ignition and fuel delivery is good, then move on to sensors.

heated sensors will read open when cold. they need to be heated to temp before they actually start reading.
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Old 02-27-2010, 09:51 AM
 
 
 
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2000, 2004, astro, chevrolet, chevy, code, cold, express, misfire, odb, oxygen, p0300, po300, sensor, van


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