Hey guys, could use some help here. My '99DII has been running quite rich, getting around 6 to 9 mpgs. The front 2 o2 sensors according to live data are stuck in open loop, running at 450 = the default setting for the ECM to go to when the heater isn't functioning properly or sending a signal.

I've got codes: 0134, 0154 Both are front o2 sensors NO ACTIVITY. Both sensors have been replaced with new AB sensors (twice), but still have codes. I had the rear o2 codes as well before replacing with new sensors and now no codes there. I've got another "new" set from AB in box still, but finding it hard to believe i've gotten 4 "new" bad ones. Trying to test everything else out to be sure.

Thanks.

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Start by checking the 02's connectors, are they covered with oil, if so clean with contact cleaner, use some die electric on the connection and clear your codes.
If that doesn't work, PM me your number and I'll call you.

 

They were not covered in oil either time that I recently replaced them. I also used the CRC electric cleaner on the connectors both times before re-installing.
Is simply spraying in the connectors with the cleaner not enough? I know nothing about "properly" cleaning them and they were hard to get to. I have another new set of front o2's from AB that I can again install and maybe need to more "properly" clean the connectors before? The rear ones were easier and after cleaning and installing those the codes have not come back...even though my cats are apparently shot and somehow getting blown out my exhaust.

Any other ideas or culprits to check in the mean time?

 

check air filter

 

Need to read the data from the Engine Computer. If something like the Engine Coolant Temp is on the cold side the computer will accept it as a true reading and run rich w/o giving a code. Otherwise you are throwing parts at it hoping to get lucky.

 

You beat me to it. I was going to suggest something very similar. If your vehicle isn't going into closed loop, due to a temperature miscalculation, your computer is going to over fuel the engine thinking it is still in warm-up mode.

 

It seems to warm up to operating temp fine, doesn't take very lond (I know the temp gauge is quite vague and worthless).
What exactly is "closed loop" and is there anyway to diagnose a warm up issue without getting it hooked up to a comp, assuming Testbook?

I got new cats put in my exhaust along with a new muffler, no more restrictions in the exhaust or cats blowing out the pipe! It is still running rich ALL the time and I still have codes: 0134, 0154 (front o2 sensors NO activity).

Instead of just tossing in the 3rd new set of o2's from atlantic british, does anyone know how to test the o2 sensor connectors with a multimeter? I want to make sure the o2 connectors and wires are sending and receiving properly before putting in new sensors.

Thanks!

 

A bad coolant temp sensor would cause the symptoms you describe. Tells the computer when the engine is warm and to close the loop.

Easy to check the sensor with a multimeter. Should be 300 ohms when warm IIRC.

 

1. the "ECT" engine coolant temperature sensor, right?
2. That is located behind the alternator and in the inlet manifold.
3. I should get the car warm, then shut down, remove alt, and test while in?
Or do I remove the sensor from the inlet manifold?

Sorry but I need to be spoon fed still.

Thanks again.

 

I had the same problelm running rich so rich it eventually fouled the plugs. Put new O2 in but still got code for no activity. My mechanic thought it was a faulty ECU. Finally took it to L.R. dealer and they determined it was a fuse. F2 15A They replaced the fuse and it is running much better. Now my cats seem to be disintigrating and sound horrible but the car is running better. By the way how long can you run with disintgrating cats?