Trouble codes


Well-Known LVC Member
Apr 5, 2004
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I have codes P1000, P1234 and P0174 now after clearing my codes they re-appeared after about 150 miles of driving. Before this I had cleared the DTC's after getting P0174 & P0171. I thought the 0171&0174 were o2 codes usually thrown by a vacume leak or dirty maf and the P1234 was a fuel relay or computer not receiving information from the fuel pump or relay is this correct or any ideas on how to fix these errors.

Also could the P1234 code in any way cause the other codes to throw?
P1000 will go away after problems are fixed, ignore that for now. P0171 and 174 are as you stated, dirty MAF try cleaning it with electric cleaner. Make sure all vac hoses and connections are leak free and also leak free from air filter to top of motor. Havent heard to much about leaky intake gaskets on lincoln motors. P1234 is also as you stated my book says also to check fuel shut off inertia switch in the trunk,faulty switch can set that code. Good luck I hate check engine lights.
Ok i'll try cleaning the maf today, ill take a look to see if a pin got bent plugging the inertia switch back in. Though i don't have a meter to actually check it but it does cut off fuel when unplugged so im thinking it may be the fpdm module. But I may end up taking it to the dealer since i cant check it and don't want to start replacing parts that may be fine. Any idea what happens when the code is thrown is performance affected, i.e. does it use preset fuel pressures since the sensor is offline?
Fuel pressure is regulated by vacuum at fuel pressure regulator. That wont change, but performance can change because once an input to the ECM is lost the ECM will use other inputs to manage itself. Lets say you lose a throttle position sensor the ECM will use other inputs to make up the difference or kinda estimate so the engine doesnt just die in the middle of the road. The problem is since the ECM doesnt have precise readings it cant vary timing and fuel delivery at its wide range so it runs at a narrower parameter. Hope it sorta makes sense.

had the same codes ! turned out to be runner seals on the lower intake creating a vacuum leak !

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