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Discussion Starter · #1 ·
Week before last I had an oil change and tires replaced on my SLX. It was running fine. The mechanic put on the wrong size tires but replaced my smaller ones the next day with the same as the new ones. Truck was running great all week. We had a snow storm and cold snap and the truck continued to run great.
Parked it over the weekend and on Monday I noticed it was low on power and felt like it was missing and the check engine light came on. Took it to the mechanic and he pulled the codes then cleared them then told me to test drive it to work (1 mile away). Truck was ok for about a half mile then the check engine light came back and power dropped off again.
Took it back to the mechanic this morning he found some ice up under the car around the sensors and the fuel filter was old, he replaced it. He told me it still had problems and to return it on Monday so he could try to find the issue. On my way home I found it was way worse than it was before and almost didn't make it home, seems it gets worse the warmer the engine gets. The more gas you give it the worse the problem becomes and it starts back firing.
Here are the codes he gave me. I hope someone can help.
P0137 (Low B1)
P0157 (Low B2)
P1171 (Fuel System Lean During Acceleration)
P0300 (Misfire)
 

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P1171 is a failure detected during a power enrichment test which indicates there is a fuel delivery problem. It is highly probable the misfire and O2 sensor issues are related to the fuel delivery problem. You may have a clogged fuel filter or defective fuel pressure regulator or defective fuel pump or water in the fuel.
 

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Discussion Starter · #3 ·
Thanks Buster28, I will bring this to the MECHs attention.

He did replace the fuel filter. Is it possible the total loss of power now is from ruined catalytic converters? before I took it to him it would run ok as long as I didn't push it. Then he tells me it was backfiring like crazy and now it is just not even drivable.
 

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If the filter has been replaced, measure the fuel pressure at the test port with a gauge, it should be about 36 PSI at idle. Pour a16 Oz can of SeaFoam motor treatment into the gas tank, it can help if you have water in the fuel. The backfiring and downstream 02 sensor problems can be caused by water in the fuel, it does not take much water to cause problems. You can worry about the cats after you solve the fuel problem.
 

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You have a left and right side catalytic converter and four O2 sensors. The two O2 sensors closest to the engine, B1S1 and B2S1, control the fuel mixture. The two located after the catalytic converters, B1S2 and B2S2, monitor the performance of the catalyst. Prolonged driving under misfire conditions can cause the catalyst to melt down and destroy the converter. Replacement is about $500 each plus labor.
 
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