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Discussion Starter #1
some searching shows no one really replacing or dealing with this...anyone know where the coolant temperature sensor is for the ECU on H6 engines?

At 200,000+ miles I'm looking to replace mine since they are cheap/easy and cause issues on the 4 cylinder jokers.
 

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Discussion Starter #3
Behind the dipstick on the head. See Pic.
great, thanks. bonus - looks easily accessible!

have you seen any of the H6's CTS's being replaced?

i see folks mentioning issues, codes with 4 cylinder EJ stuff but haven't seen the H6's mentioned yet.
 

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Nope. Mine is still OE, hitting 187k miles. If the ECM is throwing a temperature code, P0128 in Global OBD II, as in Coolant below regulating temperature, its the thermostat. Varify it with a scan tool by watching the ECT values.

If an ECT goes stupid, it will send -4 F or lower to the ECM even though the temperature is much higher. I have seen H4 ECTs show -40 F and 325 F. They are identical sensors, so I don't know what's up with the H6's sensor lasting. Come to think of it, newer H4 sensors tend to last a long time also, when the coolant is kept clean and there's no tap water in the system.
 

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Discussion Starter #5
Thanks. I'm not tracking any issues, but I've seen folks mention that CTS is responsible for H4 poor performance without throwing a code so I was wondering if it's worth replacing as preventative maintenance. my 200k H6 runs perfectly fine, gas mileage seems low but I live in the mountains and our use is not very conducive to good gas mileage or consistent monitoring so not sure if it means anything. Can they "degrade" without a CEL?
 

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Just look at the data for a few days, compare the temperature reading with the gauge on the panel to verify its working.

Its a thermistor. They tend to last a long time until it overheats enough creating an open in the circuit or minerals from tap water effects the voltage change.

Fuel economy has many factors. Check off the list of known issues and go from there. If you can stream the data, look at the long term fuel trims, both banks, at idle and again at 2500 rpm to see what the computer is doing. Look at it while driving, not like texting and driving, but have someone drive while you look at the data or record it if you have the capability and look at it after. LTFT can give you a good idea as to what the ECM is doing to maintain engine performance.
 

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2004 Subaru OBW L.L. Bean H6. 2003 Subaru OBW L.L. Bean Former 2001 Subaru OBW VDC owner.
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some searching shows no one really replacing or dealing with this...anyone know where the coolant temperature sensor is for the ECU on H6 engines?

At 200,000+ miles I'm looking to replace mine since they are cheap/easy and cause issues on the 4 cylinder jokers.
Grossgary, did you ever find out where that sensor is? Have you replaced yours?
 

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2002 3.0 VDC Wag + 2018 2.5 Leg Ltd
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Grossgary, did you ever find out where that sensor is? Have you replaced yours?
you got to put a @ in front like this, @grossgary

unless he is subscribed to his own old thread.
 

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Grossgary, did you ever find out where that sensor is? Have you replaced yours?
you got to put a @ in front like this, @grossgary

unless he is subscribed to his own old thread.
Eagle I'm on my phone, not sure what you mean though, you mean I gotta quote him, and literally put @ in front of the quote? Ugh, is everything a challenge today or what?
 

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Eagle I'm on my phone, not sure what you mean though, you mean I gotta quote him, and literally put @ in front of the quote? Ugh, is everything a challenge today or what?
either should work. (my fault, I did not catch that you quoted him...sorry,...having my 3rd cup of coffee now).

I just quoted you, and now I will mention you @Lverano

so you should get both,...
 

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2004 Subaru OBW L.L. Bean H6. 2003 Subaru OBW L.L. Bean Former 2001 Subaru OBW VDC owner.
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2004 Subaru OBW L.L. Bean H6. 2003 Subaru OBW L.L. Bean Former 2001 Subaru OBW VDC owner.
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1,171 Posts
Eagle I'm on my phone, not sure what you mean though, you mean I gotta quote him, and literally put @ in front of the quote? Ugh, is everything a challenge today or what?
either should work. (my fault, I did not catch that you quoted him...sorry,...having my 3rd cup of coffee now).

I just quoted you, and now I will mention you @Lverano

so you should get both,...
Got it, I'll mess with the concept later when I'm at my computOr
 

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Discussion Starter #15
Will it hurt anything to spray some kroil on the threads of the old sensor in the meantime, while I await the arrival of the new sensor? .
nope, have at it. i wouldn't dump 10 gallons of it in there as tempting as that is in the rust belt...:grin2:
 

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2004 Subaru OBW L.L. Bean H6. 2003 Subaru OBW L.L. Bean Former 2001 Subaru OBW VDC owner.
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Will it hurt anything to spray some kroil on the threads of the old sensor in the meantime, while I await the arrival of the new sensor? .
nope, have at it. i wouldn't dump 10 gallons of it in there as tempting as that is in the rust belt...
Gracias señor GrossGary.
 

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2004 Subaru OBW L.L. Bean H6. 2003 Subaru OBW L.L. Bean Former 2001 Subaru OBW VDC owner.
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Thanks. I'm not tracking any issues, but I've seen folks mention that CTS is responsible for H4 poor performance without throwing a code so I was wondering if it's worth replacing as preventative maintenance. my 200k H6 runs perfectly fine, gas mileage seems low but I live in the mountains and our use is not very conducive to good gas mileage or consistent monitoring so not sure if it means anything. Can they "degrade" without a CEL?
I hit mine with some kroil, I just hope the dahn thing does not snap off. Will fluid spew outbof the block on the H6? How was yours getting it out? A real bugger or what?
 

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They're brass with thread sealant in an aluminum head. I'd say the odds of one seizing up are pretty slim. If they do, it's right on top of the motor and I'd guess a good easy-out would remove whatever's left of it.
 

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They're brass with thread sealant in an aluminum head. I'd say the odds of one seizing up are pretty slim. If they do, it's right on top of the motor and I'd guess a good easy-out would remove whatever's left of it.
Sounds very reassuring. I guess as long as I don't do anything half aszed, like use the wrong size socket, or not seat the socket completely over it, I should be ok.
 

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They're brass with thread sealant in an aluminum head. I'd say the odds of one seizing up are pretty slim. If they do, it's right on top of the motor and I'd guess a good easy-out would remove whatever's left of it.
Yep went pretty easy like you said.
 
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