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  #31 (permalink)  
Old 12-23-2003, 10:25 AM
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DMorris is right, Sue, your car is OBD-I. The O2 sensors are a very good guess. They get into a vicious cycle where they get lazy, the injectors run rich, the rich mixture makes them even lazier, and so on. I believe your model only has 1 sensor, its down by the collector. I don't believe they started putting one after the cat until a couple of years later, but you might check as they would both likely be cooked.

Good luck and Merry Xmas!

Bluesman
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Old 12-27-2003, 06:37 AM
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Lightbulb 02 Sensor & E Check

I'm back. I did the check engine light flash sequence where you insert the key without starting the car and turn it on, off, on, off, on, and count the flashes. It gave me a code 51, which according to the computer code list I found on the internet for my car (94 Chrysler LHS) means that the oxygen sensor is stuck at lean position. I realize that if I've driven it this way for a while, it could have damaged the catalytic converter. But wouldn't I have noticed something if it's been this way for a while? And why does it always give you the # 12 code first (Memory Standby Power Loss - battery cable disconnected)? Is it because I initiated it by doing this procedure and that's the code you should get first? I checked it a few times and each time I had 1 flash, pause, 2 flashes, pause, 5 flashes, pause, 1 flash pause, 5 flashes, pause, 5 flashes pause.

I'm still taking my car to my mechanic, hopefully this week if he can work it in, but I'm trying to get a handle on repair costs, especially since I just finished with all the Christmas expense. How accurate is the key code procedure? How expensive are catalytic converters? Lastly, could some other malfunctioning part be causing this? Where is the 02 sensor located, is it easy to get to as in, can my hubby replace this part or are we better off just taking it in and hoping it doesn't lead into a lot of parts having to be replaced? I know that when the map sensor went out it was right on top, easy to get to and looked like I could even change that part myself.

Thanx for all of your input.

Sue
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  #33 (permalink)  
Old 12-27-2003, 08:00 AM
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Hi Sue,

Ok, were going to try and get into this one. According to my Internet info, which is never as good as any professional tech manuals available at work, a code 51 means that the computer has maxed out it's fuel injector pulse to try and offset a lean condition. this is not the same as a code 21 that would indicate specifically that the O2 sensor is switching too slow or not at all. PCM's (Powertrain Control Modules) are programed with what we call 'adaptive strategies'. When a car is first started it operates in what we call 'open loop' meaning it is in 'non-feedback' operation using a preprogrammed set of values to operate. As the engine warms up she enters 'closed loop' operation and is now a 'feedback' system using inputs from several sensors to maintain a proper fuel/air ratio. The PCM is only programmed to either richen or lean out the mixture so far. It does this by changing the injector pulse and this can be seen by watching the long term fuel trim info on a scanner. Now lets say you develop a vacuum leak, the PCM will start to increase fuel trim to offset this. As the leak increases so does the fuel trim as the PCM keeps increasing fuel delivery to stabilize the air/fuel mixture. All PCM's are designed to adjust to a point and then a 'fault code' will be stored if that point is exceeded. This is most likely what happened to your car. The PCM saw the mixture leaning and kept increasing duel delivery until the 'fault code' was set. The million dollar question is 'why'? The O2 sensor could be going bad causing a 'false' input to the PCM making it richen the mixture, or you could have a vacuum leak that the PCM could not compensate for (broken vacuum hose, cracked intake gasket, etc.). This part of the diagnostic process is where some equipment and a little know-how is needed. To rule out the O2 sensor a tech would introduce something into the mixture to richen it and monitor the O2 sensors signal. If the sensor responds normally to the testing then we would start to look for vacuum leaks or other problems. This code as I explained above is a little more involved sometimes than some codes are. I'm not real familiar with the 3.5 engine but I have seen the Chrysler 3.3 V6 engines develop similar problems because of cracked intake plenum gaskets. As far as "where is the O2 sensor located", it is in the exhaust anywhere from the exhaust manifold to the cat. converter. It has to be before the converter since it measures the amount of oxygen in the exhaust pre-cat. It looks kind of like a spark plug in your exhaust with wires coming out of it. They make a special socket to remove/install them and often a little heat from a torch is required during removal. In approx. 1996 cars went to OBDII and added O2 sensors after the converters called 'downstream sensors' so the PCM could actually 'see' the difference between the gasses going into the converter and the gasses coming out of it. This finally allowed the PCM's to actually monitor whether or not the converters were working correctly or not. Whether or not you want to do a little 'guess' repairing is up to you. If the O2 sensor is in a decent place your husband may be able to rent the socket needed from your local auto parts store and replace it himself. My suggestion would be to get someone you trust in there to do a little more investigating before spending too much on unneeded parts. Hope this has helped, if something was missed asked again.

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Old 12-27-2003, 08:22 AM
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02 Sensor

I can't find the post I made earlier, so at the risk of looking stupid, I'll copy and paste it here to see if it shows up. Sorry if it gets posted twice.

Here it is:

I'm back. I did the check engine light flash sequence where you insert the key without starting the car and turn it on, off, on, off, on, and count the flashes. It gave me a code 51, which according to the computer code list I found on the internet for my car (94 Chrysler LHS) means that the oxygen sensor is stuck at lean position. I realize that if I've driven it this way for a while, it could have damaged the catalytic converter. But wouldn't I have noticed something if it's been this way for a while? And why does it always give you the # 12 code first (Memory Standby Power Loss - battery cable disconnected)? Is it because I initiated it by doing this procedure and that's the code you should get first? I checked it a few times and each time I had 1 flash, pause, 2 flashes, pause, 5 flashes, pause, 1 flash pause, 5 flashes, pause, 5 flashes pause.

I'm still taking my car to my mechanic, hopefully this week if he can work it in, but I'm trying to get a handle on repair costs, especially since I just finished with all the Christmas expense. How accurate is the key code procedure? How expensive are catalytic converters? Lastly, could some other malfunctioning part be causing this? Where is the 02 sensor located, is it easy to get to as in, can my hubby replace this part or are we better off just taking it in and hoping it doesn't lead into a lot of parts having to be replaced? I know that when the map sensor went out it was right on top, easy to get to and looked like I could even change that part myself.

Thanx for all of your input.

Sue

I found my post and the response. I'll study it.

Thanx,
Sue
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