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david, Auto Service Technician
Category: Ford
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Experience:  Certified Master Technician,Certified in diesel & gasoline engines
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2004 F150: runs rough..fuel pressure..oil temp sensor reading..volts

Customer Question

2004 F150 5.4 runs rough, no power, wont rev up. It has 40psi fuel pressure, only code is oil temp sensor reading high. With my scan tool it says the oil is 900,000 degrees and is getting 5 volts. If I jump the sensor plug, it reads 32 degrees and 0 volts so I don think a wiring problem rather in the ecu perhaps. The engine ligt and wrench light come on occasionally but do not stay on. I am wondering if the oil temp reading high would cause limp mode and if that is why it is running badly and if I should replace the ecu or just have it flashed?
Submitted: 4 years ago.
Category: Ford
Expert:  david replied 4 years ago.
Hi thank you for your question hope this helps.

Yes the oil temp sensor reading high would put the truck into limp mode.

Can you tell me the code you are getting this will help me narrow down the source of the problem.
Customer: replied 4 years ago.
Hi, if I run a KOEO test it comes with; P1000 drive cycle test not completed, P1184 oil temp sensor out of range, and occasionally P1288 cylinder head temp out of range (i assume this is because it is so much different than the oil temp because it reads the correct temp on the scan tool)
Expert:  david replied 4 years ago.
OK I am guessing you are clearing the codes this explains the P1000 because you are reseting the memory.

When you say you jump the sensor plug is this with the plug disconnected from the sensor?

The oil temp sensor is a variable resistor it measures the temperature and sends the voltage to pin 27 on the PCM but it is also wires to the fuel rail pressure transducer sensor, witch goes to pin 32 on the PCM.

If it were me I would replace the temp sensor first It may be sending the wrong info to
the PCM, from the fuel rail pressure transducer sensor. Because 900,000 degrees is just a little out of the sensors range know what I mean.


Although it could be the PCM because you are not getting a engine coolant temp sensor temp out of range, along with the, cylinder head temp out of range. But start with the cheaper parts first.
Customer: replied 4 years ago.
I did replace the oil sensor to no avail. When I say I jumped the oil temp sensor, I just stuck a wire in both the holes in the plug to make full continituity. If I do that it reads 32 degrees but still a sensor fault and still runs badly. It seems to run ok when it starts cold for a few seconds but I think that is because it does not read off the sensors at first correct? How can I tell if it is limp mode or running badly for another reason?
Expert:  david replied 4 years ago.
This is a strange one, you see the sensor is should be sending info all the time.

It seams that as soon as the sensor sees the oil is worming up is were the problem starts.
What is hard to understand is if you jump the sensor every thing runs ok right?

So we know the wiring to and from the sensor are good, So the only thing it could be is the PCM not interpreting the signal right. I would replace the PCM with a new one or tack it to the dealer to be re flushed / tested.

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