Hi all - 98 Outback 2.5L. Can anyone shed any light on this error code. What is a "fuel temperature sensor" for anyway? Where is it located? Can I change it myself?

 

Cheers

Hi. DTC P0183 - FUEL TEMPERATURE SENSOR A CIRCUIT HIGH INPUT

 

DTC DETECTING CONDITION: Immediately at fault recognition

 

AFIAK this sensor is in the fuel tank on the fuel pump assembly. If you look under the carpet behind the rear passenger seat, you should see a sort of rectangular access cover. Underneath this cover is the connector to the fuel pump. Make sure that all looks good. Could just be a bad connection. Sometimes when you have the fuel filter replaced a place will unhook this connector. When it's reconnected it might not be fully seated or have a bent pin or something.

Thanks Porcupine!

Ok so I found and removed the access panel you mentioned and found the connector you described so I disconnected, cleaned and reconnected it. I cleared the code and started the engine - the code reappeared instantly.

 

Any other suggestions?

I recommend you check the continuity of the wiring using a ohmmeter. There may be a problem with it or, the sensor itself may be bad. I'm not sure what the resistance of the sensor should be. You should see something though I would think. If the sensor leads show 'open' then it is most likely the problem.

Excuse my barging in, but what is the function of this sensor?

My guess is maybe the ECU uses the fuel temperature in A/F ratio control. I saw a post with this code on subaruforester.org not sure if s/he ever fixed it. The manual lists a whole bunch of wiring and resistance checks.

Hi All - finally I had the time to take care of this annoying problem. Here is waht I did

 

1) Located access hatch behind rear passenger seat

2) Remove outer access hatch and disconnect power to fuel pump.

3) Start engine until it stalls (depressurize fuel system)

4) Remove the 3 fuel lines

5) Undo all bolts and remove fuel pump and fuel pump assembly

 

- I noticed that a wire had come off its contact point which is what I believed to be the FTS leading to an open circuit and therefore the "high input" error

 

6) Soldered the wire back on and reassemble

7) Disconnect the negative battery terminal for 5-10 minutes.

 

Presto - fixed.

Ok good fix and thanks for the update!

 

I can't update my previous post because it's too old, but the ECU uses the fuel temp sensor input to know when it can do the evap fuel system integrity test.

Thanks for the update and thanks also to P73 for the fuel temp sensor explanation.

Ok good fix and thanks for the update!

 

I can't update my previous post because it's too old, but the ECU uses the fuel temp sensor input to know when it can do the evap fuel system integrity test.

 

Just wondering why my gas mileage became so poor when it became cold? Once I fixed this it was ok again. How does the FTS affect emmissions?

Not sure why this would impact mileage. It uses fuel temp to know when to run the integrity test. It basically makes sure you have no leaks in the fuel system, which would allow raw fuel in the atmosphere. In an endwrench article for enhanced evap soobs it says:

 

To test the integrity of the [fuel] system, the system shuts off all access of the tank to the outside atmosphere. [then a bunch of other steps].

 

The testing of this system is only conducted once per drive cycle and only under very specific conditions:

• The fuel tank must contain less than 9.6 gallons of fuel.

• The fuel temperature must be less than 113°F.

• Engine speed must be over 1500 RPM.

• Vehicle speed over 28 MPH.

• Throttle position must be mid-range.

• Intake manifold vacuum must be equivalent to cruising vacuum.

• 455 seconds must have elapsed since engine start.

After spending a lot of time looking at the thermometer in the tank, it occurred to me that if it were an ecu input, it should be 5v or less. I found a diagram of the ECU pinout, and there is a pin #25 labeled for fuel temp sensor. Backprobed it and found 4.99v. Tried a 1k resistor to ground, and it pulled voltage to 2.13. ECU bought it immediately. Removed resistor, and P0183 returned. Put resistor back in, and code cleared and stayed clear. There must be another sensor somewhere, but the thermistor is for low fuel light only. I'll post a diagram shortly.

MSA5TCD97L3907-ECU-TCU.pdf

Edited June 29, 20196 yr by Flying_W
added file