When the ecu doesn't know the afr, it cannot provide the engine with the right amount of fuel.
You're talking about a defective car. For all you know, the engine light could have been defective too.
If your car is working properly, the ecu will give a warning when the mixture gets leaner than expected by the mapping. Thats what p0171 (or p0174) is for.
If the ecu wouldn't give a p0171, it wouldn't have the slightest idea how much fuel it would be putting in the enigne in the first place, so it's defective already. No warning light would have ment a defective ecu, not a defective fuel pump. The pump and injectors cannot provide what the ecu isn't telling the pump cq. injectors what to do.
If obd2 and related protocols isn't a failsafe (or at least a warning), nothing is. Everything goes by obd2 and its (CAN)management: speedo, revs, coolant temperature, throttle..... Everything!
Last edited by GuidoK; 12-15-2012 at 01:58 AM..
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