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Q: Codes P0174 and P0300 on 1999 Isuzu Trooper

Can both these codes be caused by the mass air flow sensor
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not likely. you have a vacuum leak on bank 2 for 174. the missfires are most likely plugs, coil or the same vacuum leak.

Thanks,but i just replaced all the plug and had one coil pack bad.Engine idles fast . have changed throtle,map sebnsor and egr valve.all coil packs are firing.
how did you check the coils?? a lot more to checking them than just looking for spark. do not discount the possibility of another coil failure.


The coils are best checked by a scope from a shop. they can verify output and see any failures. not as simple as it sounds.

Basically this means that an oxygen sensor in bank 2 detected a lean condition (too much oxygen in the exhaust). On V6/V8/V10 engines, Bank 2 is generally the side of the engine that doesn't have cylinder #1.
Note: This DTC is very similar to P0171, and in fact your vehicle may show both codes at the same time.
Possible causes:
•The MAF (Mass Air Flow) Sensor is dirty or faulty. Note: The use of "oiled" air filters can cause the MAF to become dirty if the filter is over-oiled. There is also an issue with some vehicles where the MAF sensors leak the silicone potting material used to protect the circuitry.
•There could be a vacuum leak downstream of the MAF sensor.
As for the p0300 you may have a diffrent problem. This code is for a random misfire and is not cylinder specific. The cause of your other code may be causing this problem. Fix the p0174 first if doing this on your own then approach the other problem if the p0300 still exist after fix.
Thanks, no vacuum leaks,cleaned mass air flow,replaced throtle position,map sensors and EGR valve.
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