Questions and Answers

Dodge Grand Caravan Needs O2 Sensor Q. I have a 1996 Dodge Grand Caravan, V-6 engine, automatic transmission with 120,000 miles on it. The Check Engine Light came on and I had it looked at by a mechanic. He said the log recorded an event 15 starts ago that the upstream oxygen sensor detected lean mixture. He reset the log, Check Engine Light out, and said if it came back on it was probably the oxygen sensor again.

The Check Engine Light came on about a week later and is still on. I consider myself mechanically inclined, but the days of my old Chevy 350 sans pollution control are gone. You need electronic diagnostic equipment priced out of my range any more.

My questions are, "Where is the upstream oxygen sensor located? My understanding is in the manifold, but can it be reached without disassembly? And how do I replace it?" Also, "How is the Check Engine Light cleared?"

I thank you in advance for your assistance.
Kevin
Jefferson City, MO

A. The original DTC would be a great help here. Otherwise all I can do is make an assumption based on a description rather than focus on an actual code. I stopped going through 2000 some odd codes to try and match up a description with a number. It just takes too long and it's not fair to others waiting to get their questions answered. If you want precise information, you need to give me precise information.

The fact that a lean condition is being detected by the oxygen sensor is an indicator that the sensor itself is probably working fine. The upstream sensor is located in the rear exhaust manifold.

A lean condition is more likely caused by another malfunction in the fuel delivery system. Something as simple as a dirty fuel filter or fuel pickup strainer can starve the system for fuel enough to cause your on board diagnostics to alert you of the condition.

It could be a little more complex, such as a fuel pressure regulator or a sensor giving incorrect readings to the control processor. A fuel pressure gauge should reveal the simple causes such as a blockage etc.

Once the lean condition is corrected the system will actually reset itself after several driving cycles and the light will stop coming on.