Repair Topics / Engine Sensors-1 / Engine Sensors-2

Engine Sensors - Computer Sensors - ECM Sensors Questions

Question: 1998 Mitsubishi Mirage mileage: 90,000. I am replacing the exhaust manifold. Old manifold has a some sort of sensor screwed into it, but the new one does not have a port for the sensor. Can the car function adequately without the sensor? What is the sensor?

Answer:   The sensor you are referring to on the exhaust manifold is the oxygen sensor. It is an extremely important part of the computer management system for your engine.

Question: 1996 Mazda 626 mileage: 70,000. What are all the problems that a failed oxygen sensor causes if I keep driving my Mazda 626 (96)? Will my car quit on me or anything? What am I in danger of as far as hurting my car? I just need to get paid to have the money for 2 oxygen sensors.

Answer:   Oxygen sensors read the fuel mixture in the exhaust and send the information to the computer. The computer then, adjusts the fuel mixture. By not replacing faulty oxygen sensors, your can expect that your check engine light will come on accompanied by erratic idle and poor running and fuel mileage. Your exhaust system could sustain damage by driving it with faulty oxygen sensors. They should be replaced as soon as possible.

Question:   1999 Ford Escort mileage: 86,500. Garage suggested several possible problems starting with Oxygen sensor - cost of repair $200. My problem is that he does not know if this is the problem, and that I will have to keep on paying for every fault finding repair even if that's not the one! Can you help with diagnosis and the best way forward? PLEASE.

Answer:   It is possible that the oxygen sensor is faulty. The sure fire way of finding out is to scan the computer for fault codes which will pinpoint the malfunctioning component.

Question: 1998 GMC Sierra mileage: 70,000. The service manual for my GMC Sierra tells me that my truck has 4 oxygen sensors. They are designated: Bank 1 Sensor 1, Bank 1 Sensor 2, Bank 1 Sensor 3, and, Bank 2 Sensor 1. The manual does not clearly indicate the location of each of these sensors. A GMC technician tells me that the term "Bank" refers to a particular side of the engine - Bank 1 refers to the side with cylinder number 1...the driver's side (as the plug wires are numbered 1,3,5,7). You'd think it would be easy to deduce the placement of each oxygen sensor. Here's the problem: Only one oxygen sensor lies beneath Bank 1. The other three are under Bank 2... two in front and one behind the catalytic converter. My information seems to be contradictory. Error code P0153 tells me I need to replace Bank 2 Sensor 1. Can you verify its location? Thanks.

Answer:   The first oxygen sensors down the exhaust pipe are the primary sensors (1) the sensors after the exhaust is sensor secondary (2) bank one is the side with number 1 cylinder (drivers side)

Question: 2002 Dodge RAM 1500 mileage: 85,000.  Would a bad oxygen sensor (upstream) cause a truck to hesitate during acceleration in low gears? What causes these to go bad?

Answer: It is not likely for an oxygen sensor to cause the poor running you are experiencing.  It sounds more like a clogged fuel filter or a failing fuel pump. Oxygen sensors eventually burn themselves out due to the heat of the exhaust.

Question: 1999 Toyota Tercel 4 cyl mileage: 91,000.  Dear Bob and Ken: My problem concerns my Toyota Tercel, 91000 miles, 4-speed manual transmission, most recent oil change was about 1800 miles ago, and no major repairs since purchasing the car at 40000 miles.   I recently made a 1600-mile trip from Virginia to Colorado; I had the oil changed, fluids topped-off, and air filter replaced.   Additionally, I had an emissions inspection done a few weeks before, and the results were excellent.  Approximately half way through the trip and some very bumpy interstate driving in Arkansas and Oklahoma, my "Engine" light came on.  I pulled over immediately to check under the engine, checked the oil level, belts, hoses, etc. and found no noticeable irregularities, except that the overflow container for the radiator fluid was empty.  There was still plenty of fluid in the radiator itself, but I replaced the fluid/water mixture anyway.  I noticed no odd smells or drivability difficulties, so I continued driving.  I stopped overnight and the following morning, I checked my owner’s manual and it said that this light comes on due to a problem with the engine's electrical system.  Being that the roads were rough, I suspected maybe a fuse had been knocked out, so I removed, inspected, then replaced all of the fuses.  I started the car and the engine light was off.  I continued driving, but after about 6 hours of interstate driving (70-80 mph) the light came on again.   Still, I did not notice any smells, sounds, or drivability problems.  I continued to drive as I was in the middle of nowhere and arrived in Colorado, still with the engine light on.  I spoke with a technician about this before and his recommendation was that the oxygen sensor could be the problem.  I have researched the function and possible problems of the O2 sensor and it seems like if that were the culprit, my exhaust would smell like "rotten eggs" OR produce a black smoke (depending on lean or rich mixture).  Is this correct?  Or could the sensor be malfunctioning WITHOUT a real problem with the mixture?  What type of problems could develop with continued driving?  Could there be another cause to the engine light coming on?   Is there some way to check the sensor myself without having to take to a mechanic?  Could the missing radiator fluid have caused something to go wrong (I have noticed no leaks in the overflow tank since)?  Could the change in altitude cause something?  I apologize for the length of this, but wanted to make sure to get all of the information here.  Thank you in advance for your help!

Answer: You probably do have a faulty oxygen sensor. Replace with new to recheck system.  If your problem persists, then scan the computer for fault codes.   Oxygen sensors go out of range at times, but still work.

Repair Topics / Engine Sensors-1 / Engine Sensors-2

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Check Engine Light