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How to replace fuel temp sensor


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33 replies to this topic

#1 joutback

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Posted 21 November 2003 - 01:25 AM

Finally, I have found a site dedicated to Subarus. Hi all.

I have a '00 OBW with CEL on. I've taken to the dealer and they said the fuel temp sensor is bad and needs replacement. My questions are what's involved to getting it replaced by myself and is there a diagram or procedures on the web that I can follow?

I have parked the car in an unleveled ground, front on concrete and rear on grass, and the CEL went off. However, it came back on when I drove the car for five minutes on the road. This puzzled me. I don't think the ground level could affect the sensor's working condition but could it? And 2cents is appreciated.

#2 Legacy777

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Posted 21 November 2003 - 08:55 AM

To be quite honest, I have never heard of a fuel temp sensor. Are you sure that's what they said?

If so, I'd suggest going some place else for a second opinion. Most autozones will pull the codes for you. They won't clear them, but they'll usually pull them and tell you what they are. There's a few other autoparts places that will do it as well.

#3 Skip

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Posted 21 November 2003 - 09:27 AM

Josh
I bet they said fuel (injection) temp sensor.

J Outback, do as Josh says to make sure.

Sorry I can't help but somebody here can I bet

#4 Scoobaroo

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Posted 21 November 2003 - 10:01 AM

I'm betting that they mean the coolant temperature sensor for the fuel injection system.
No such thing as a fuel temp sensor as far as I know.

#5 Phillip

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Posted 21 November 2003 - 12:00 PM

Yes, there is a fuel temperature sensor on your car. My 1999 factory manual shows it very near the fuel level sensor at the rear of the car. I'd bet it's part of the fuel pump/fuel meter assembly, but don't know for sure. I'm a mechanic in a domestic repair shop with limited Subaru experience (just bought one a few months ago); GM & Ford both also use fuel temp sensors. Typically when the CEL illuminates with a fuel temp sensor code, either the fuel filter is partially plugged, the pump is defective, or the sensor is bad. The fuel continuously circulates from the tank to the injection unit and back to the tank again whenever the pump is running. Any restriction (plugged fuel filter or pinched line) will cause the fuel to heat up and trigger a code. If no one else knows where the sensor is located, I'll review my factory CD service manual and see what I can find for you.

#6 Legacy777

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Posted 21 November 2003 - 02:12 PM

hmm....yeah double check the code to make sure.....I've never heard of anyone driving a subie get one of those codes.....but like Phillip mentioned, it could mean there are other issues such as the filter and what not that needs to be looked at.

#7 joutback

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Posted 21 November 2003 - 06:24 PM

Thank you.

I have changed the fuel filer and spark plugs on it and thought CEL would go out but it has not. I'll take it to Autozone to double check the codes. To be continued...

#8 alias20035

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Posted 22 November 2003 - 12:44 AM

Never heard of a fuel temp sensor on a Subaru, perhaps they are just there and very rarely go bad......

Coolant temperature sensor failures are very common, let us know when you recheck the code.

Just curious, is your car a California/north east US emmisions model, or just a normal (used to be referred to as 49-state) car?

Have Autozone reset the ECU (or disconnect the negative battery cable for fifteen minutes) and see if the code comes back, you can fix a problem but the ECU will not clear the code on its own....

Subaru gas tanks are a little weird as they stradle the driveshaft and rear differntial. The pump is on the right side, and there is a venturi setup which uses the fuel return pressure to pump gas from the left side to the right over the "axle hump".

If the newer Legacy/Outbacks are like my 1993, there should be two access panels under the carpet immediately behind the rear seat. The right one is for the pump and should be were the sensor is, unless Subaru has gotton creative by placing it somewhere else.

BTW: in tank pumps are good because they are submerged in fuel which acts as a heat sink to keep the pump cool. Running the car on empty a lot can lead to premature failures of the fuel pump. Ideally you should always refill BEFORE the low fuel light comes on.

Also in winter you should keep the tank above 1/2 full all the time as doing so will reduce moisture buildup in the tank which will reduce the chance of a frozen fuel line, and reduces corrosion in the tank. It also means that you will have "extra" fuel in an emergency.

Tomorrow I am doing some audio system wiring in the area, so I am going to check the fuel pump wiring harness under the rear seat on my 01 Outback to see if it has extra wires (for temp sensor) compared to my 93 Legacy.

Not sure what a fuel temp sensor would do, perhaps adjust the engine running for fuel evaporation rate (which slows with lower fuel temp), or adjusts the evaporative purge system. Diesels have had fuel temp sensors for years, but diesel turns to sludge at about -15 C.

You should be able to check the resistance of the temp sensor to see if it works properly. Use a glass of cold water, check is temperature with a thermometer, and then check the resistance. Recheck with warm water. There should be a table in the maintainance guide which indicates the resistance at various temps. Perhaps Phillip's CD has this table....

You could also test with the sensor still in the car if the car has been sitting in the shade for a few hours. The fuel temp should be close enough to the air temp to verify the resistance.

My ODBII code list does not show any code for fuel temp sensor, but the book is for 96-97 models.

#9 Phillip

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Posted 22 November 2003 - 01:39 PM

The 1999 Factory (CD) Subaur Service Manual lists the following Fuel Temp Sensor Codes: PO180, 181, 182,183,184,185, 186, 187, 188, & 189, but gives no testing procedure. My Snap-On Scanner reads the sensor in degrees (not voltage) so I doub't the sensor could be accurately tested using hot/cold water and reading voltage. I've yet to find the exact locaton, but it appears to be very near the FUEL TANK PRESSURE SENSOR, which is located"Behind right rear cargo area trim panel, rear wheel area". I'll spend some time this weekend trying to find the exact location and reply later.

#10 alias20035

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Posted 22 November 2003 - 09:30 PM

Originally posted by Phillip
The 1999 Factory (CD) Subaur Service Manual lists the following Fuel Temp Sensor Codes: PO180, 181, 182,183,184,185, 186, 187, 188, & 189, but gives no testing procedure. My Snap-On Scanner reads the sensor in degrees (not voltage) so I doub't the sensor could be accurately tested using hot/cold water and reading voltage. I've yet to find the exact locaton, but it appears to be very near the FUEL TANK PRESSURE SENSOR, which is located"Behind right rear cargo area trim panel, rear wheel area". I'll spend some time this weekend trying to find the exact location and reply later.



I checked the fuel pump/fuel level wiring and there do not appear to be extra wires, so the temperature sensor does not appear to be in tank. I counted four wires (ground, pump, fuel level, and low fuel light). My car is built to Canadian emmission standards, which should be similar to US 49 state (non California).

Given the location that you quote it could be within the evaporative emmisions system which is tucked up behind the right rear wheel (same location as muffler, but opposite side). I have had the interior cargo trim off of my 2001 Outback, and there is nothing related to fuel system in there, aside from the floor hatch for fuel pump access. Perhaps the 95-99 models were different.

I have had to clean some wiring on the evaporative emmisions system. Because it is behind the wheel it gets hit by stones, slush, water, road salt, etc from the wheel. My evaporative purge wiring was corroded and I got a check engine light. I disassembled the wiring harness, cleaned of the contacts, and reassemblied using and sealant. No more problem....

#11 joutback

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Posted 22 November 2003 - 11:52 PM

The code reads P0183, fuel temp sensor. Autozone did reset the code however, the CEL came back after 45 minutes of driving. And they don't have the part other than getting it from the dealer.

I tried to find the part near the fuel tank but no success. Is the evaporative emissions system look like a "black box" behind the right rear wheel? I'll look at the trim panel tomorrow.

#12 alias20035

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Posted 23 November 2003 - 02:24 AM

Originally posted by joutback
The code reads P0183, fuel temp sensor. Autozone did reset the code however, the CEL came back after 45 minutes of driving. And they don't have the part other than getting it from the dealer.

I tried to find the part near the fuel tank but no success. Is the evaporative emissions system look like a "black box" behind the right rear wheel? I'll look at the trim panel tomorrow.



I think that is where it is, but ask the dealer when you get the new temperature sensor. You could also have defective wiring like my 2001 Outback did, I got a CEL for evaporative purge valve. I cleaned the electrical connector, put it back together and all is ok two years later. I'll take a look for more wires on my 2001, the only ones that I have worked on are the ones sticking straight down which are the purge valve. But it is possible that my Canadian Subaru does not have this sensor, as our emmisions controls are different, not better, not worse, just different.

#13 Myxalplyx

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Posted 24 November 2003 - 07:23 PM

Holy crap! This is amazing! I just posted about the same problem here: NASIOC Fuel Temp Sensor

I've had this code for YEARS. I just went through motor vehicle today and failed because of this code. Someone had mentioned checking near the ECU to be sure the voltage is getting to it like it should in an older NASIOC thread. My code reads: P0183 (Fuel Temperature Sensor A, Circuit High Input). This is what I get on my Palm Pilot Pocketlogger OBDII software when I hook up to the connector near the left leg. Resetting the ECU does nothing. The code stays up. I can make other codes come and reset the ECU and everything is cleared....as a test. So I know the resetting is working as it should.

I'll be checking my ECU connector to be sure everything is cool there since I've had 2 different types of fuel controllers there in the past and the wiring may be jumbled. If you find ANY information on this joutback, please feel free to let me know. I'll be checking here throughout the night (I'm at work). :temper: Good luck!

#14 Myxalplyx

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Posted 25 November 2003 - 03:42 AM

Just was browsing the internet trying to find more information about this code.

On this site:
http://www.visi.com/...s-full-text.htm

It says this,

Code:
P0183 Engine Fuel Temperature Sensor A Circuit High Input

Description:
The comprehensive component monitor (CCM) monitors the EFT sensor circuit to the PCM for high voltage. If voltage were to exceed a calibrated limit and a calibrated amount of time during testing, the test will fail.

Possible Causes:
*Open or Short to power in harness*
*Damaged EFT Sensor*
*Improper harnes connection*
*Damaged PCM*

Diagnostic Aides
Verify EFT-PID value to determine open or short

I'm looking into this tomorrow on my car. Maybe it'll help you also. L8Rs

#15 Myxalplyx

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Posted 25 November 2003 - 04:02 PM

*Bump*

Where's all the 'tech-heads' at? We need you! :banghead: Help..... :D

#16 Legacy777

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Posted 25 November 2003 - 04:27 PM

I guess the first thing that needs to be done is determine where the sensor is?

Anyone absolutely sure where it is?

#17 99obw

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Posted 25 November 2003 - 05:18 PM

The FSM for our '99 outback shows the fuel temp sensor being part of the fuel pump and says the following:

"NOTE:
Fuel temperature sensor is a unit with fuel pump.
If replacing it, replace as a fuel pump."

#18 Myxalplyx

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Posted 25 November 2003 - 07:27 PM

Originally posted by 99obw
The FSM for our '99 outback shows the fuel temp sensor being part of the fuel pump and says the following:

"NOTE:
Fuel temperature sensor is a unit with fuel pump.
If replacing it, replace as a fuel pump."



I've had an aftermarket fuel pump on my car for years. Maybe some aftermarket fuel pumps do not have a fuel temperature sensor as a part of it. This would disconnect the wiring needed to be connected and cause a 'high circuit'.

Even still, it should be connected somewhere on the ECU. I have a voltmeter ready to test this to be sure it's getting to the ECU but can't even do that. I'll just go by what you are saying and take a look at my fuel pump. I probably wouldn't know it was it if I saw it.

I don't like fiddling around in gasoline filled areas. Welp.....we'll see. :(

#19 Legacy777

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Posted 25 November 2003 - 08:24 PM

You can probably just find the connector output for the fuel pump, find out which one is the temp sensor, and then back probe it, and or check to see if it's working properly.

#20 Myxalplyx

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Posted 26 November 2003 - 11:20 AM

joutback,
You are kinda quiet bud. Is everything ok? Did you get this resolved yet?

I just got word that there are no fuel temp sensors on the 1997 Impreza Outback Sport. Now I REALLY have problems. Guess it's time to take it to the dealership and get plenty of grease ready. *sniffle*

#21 Cougar

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Posted 26 November 2003 - 04:00 PM

I just learned about this sensor recently and I think it was the same poster on the Car Talk board that was inquiring about this.

I have the factory manuals for my '01 Outback and here is what it says about DTC 183. This means the ECM is seeing a high input from the sensor. I believe this means a high resistance in the circuit to the sensor or the sensor itself is open.

The temperature sensor is in the tank mounted near the pump. can be replaced seperately, and that you should replace the fuel level sensor also when replacing the temp sensor.

The connection to the sensor is through connector R58 on pins 5 an 6. Pin 6 ties back to the ECM on connector B136 pin 26. Pin 5 ties back to the ECM on the same connector pin 16. On the sensor side, it looks like pin 6 is the high side and pin 5 is the ground side. It may be pin 5 is isolated from ground but I can't say for sure.

The book says you should see between 4 to 10 volts on pin 6 to chassis ground with the connector removed from the pump connection if things are ok with the wiring back to the ECM.

One quick thing to look at would be to measure the voltage between pin 26 and 16 on the ECM and see what it is.

There are warnings about removing the fuel pump if the fuel level is above 3/4 of a tank and making sure the ground is connected to the assembly before putting the pump back after removal. Unless you are real intent on doing this I would leave it for the pros to do. When it comes to exposed gasoline I don't like to mess with things unless I really have to. The risks are not worth it to me.

#22 joutback

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Posted 27 November 2003 - 12:55 AM

Hi,

Yes, I did post this question on Car talk as well.

Sorry, I did not get a chance to find the exact location of the sensor. And it seems the procedure is complicated on getting this replaced.

Are there two level sensors on the tank, one main sensor and one sub sensor? I have downloaded the diagrams from the 1stsubaruparts.com site and it did not reference any temp sensors but it has two level sensors. It seems one is the wiring(main) and one is the sub (attached to the fuel tank). I don't have the shop manul to compare to so I don't know if this is correct or not.

It seems this might be a trip back to the dealer... :mad:

#23 Cougar

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Posted 27 November 2003 - 03:57 AM

Your car does have two level sensors as you say. There is a sub level sensor. I think the one that the FSM manual suggests replacing with the temp sensor is the regular one.

The temp sensor is mounted on the same cover plate the pump is on, inside the tank.

#24 Myxalplyx

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Posted 28 November 2003 - 01:33 AM

Originally posted by Cougar
Your car does have two level sensors as you say. There is a sub level sensor. I think the one that the FSM manual suggests replacing with the temp sensor is the regular one.

The temp sensor is mounted on the same cover plate the pump is on, inside the tank.



Thanks Cougar! Your input seems to be helpful. At least it's giving us a lead. I have a 1997 2.2ltr Impreza so my dillema may be slightly different than Joutbacks. I know looking at the wiring diagram for the 1997 Impreza Outaback below....

http://wac.addr.com/auto/obs/ecu1.gif
http://wac.addr.com/auto/obs/ecu3.gif

,it states that there is no fuel temp sensor on my car. I checked for a Terminal #25 like the diagram suggests but there is no pin on the ECU nor the connector in terminal #25.

There is something else that may be the culprit of my problem that I just thought about a few minutes ago. I have an aftermarket fuel pump in my car. I believe it was one that Rallispec installed years ago. Could an aftermarket pump's installation be relative to all of this?

I've never accessed the fuel tank compartment before. I folded my rear seat down yesterday and unscrewed this section just behind the passenger side rear seat that I thought lead to the fuel tank area, to access the fuel pump. I took the cover off only to see about 3 lines to go to what appeared to be the fuel tank. I've no manuals on this car since they are $600+ so I'm being careful in this area. I'll try again. Thanks!

#25 Cougar

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Posted 28 November 2003 - 12:00 PM

Hi Kevin,

You stated that your car is not supposed to have the sensor, the ECU has no wires where they should be if you did have one, and yet you get a error code on your pocket logger. Does your CEL light come on with this error code or have you had the dealer check for this code with the Subaru trouble code reader? I am wondering if perhaps your particular reader may have some sort of a glich with this specific code.

The place where you saw the fuel lines go into the tank is where the pump should be if you have an internal pump. I'm not sure about your model. On my car there is a 6 pin connector on the access plate that makes connection to the devices inside the tank. Yours may only be 4 pin since you have no temp sensor.

I know what you mean about the cost of manuals for the car. I happened to find some good used ones for my '01 on Ebay. I purchased 7 out of the 9 manuals for under $185 dollars. The two I did not get were not worth bidding more on as I could buy them for less new. You can contact Jamie at www.allsubaru.com if you want and she will sell you manuals at a reasonable discount. She saved me almost half over what my local dealer quoted me for the books. You don't have to purchase all of them either. Just what areas you are interested in, though it is nice to have the full set. Also check out Ebay and search for Subaru service manuals. You just may get luck as I did.




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