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97 Brighton, 4x4
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Discussion Starter · #1 ·
So I originally had a p0440 code. I have changed out many of the sensors that accompany this code. That code has now changed to a
p1440.
Fuel Tank Pressure Control System Low Input

My problem is I don't know what this system consist of. I have some service manuals that covered the p0440 code but none of them cover this new code.

So if some one could look up and see what this code and the steps to fix it I would be grateful. This has been a very troublesome problem and I'm close to fixing it. But I only have 1 month before emissions are due and I will fail if I don't fix this.

- The gas tank now hold pressure (Ie no leaks.)
- I have changed the drain valve.
- I have also changed another valve which I don't know what the function is because It is very specific to the 1997 year. (ei only on 1997 Subaru's.) It is under the car near the canister though.

 

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Discussion Starter · #2 ·
To show you one of the many problems I'm having. Here is a sensor which I cannot find in any service manual or wiring diagram. I'm pretty sure this might be the problem sensor. IDK were the tubing goes or what is were it connects to however. This is in the trunk on the passenger side wheel well.
 

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Discussion Starter · #5 ·
Ok, So i'm almost certain this sensor pictured above is the cause of my problems. I unplugged it completely to see what code the ECU would through. and it gave me

P1441
Fuel Tank Pressure Control System High Input

So I know this is were my problem is. I'm going to try and probably replace the sesnor and see if that works. If not I might have to track down a short in the harness somewhere. Does any one have tips on how to do this?

I took my volt meter to the plug (3 prong) and the middel is getting +5V and the two outers are working as grounds when the ignition is on. How do you know if there isn't soposed to be +12 running there. If worst come to worst I'll just rewire the whole MFer to the GD ECU. That'll teach this biatch.
 

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Discussion Starter · #8 ·
mulder on nabisco said:
The +5V is the reference signal from the ECU. The 2.3-2.7V is the signal output from the sensor that goes back to the ECU.
Make sure the ground for the sensor is properly connected as well, or it won't output any signal.
I'm thinking that the signal (2.5v) isn't getting back to the ECU. Anyone know how to test this?
 

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Discussion Starter · #9 ·
So I did some more testing. I tested the voltage out of the sensor and first I was getting ~2.0V. So I removed the sensor and discovered that it let out all the pressure in the gas tank which makes sense now. I tested it again w/out the pressure and it read 2.5V just like it should. So i'm kind of confused as to why the ecu is seeing low voltage values. Doesn't low voltage in this situation mean that indeed the gas tank is holding pressure? IDK??

I love talking to myself!
 

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Discussion Starter · #10 ·
So I unplugged the sensor from the vacuum line and got the same code p1440 low input. So I'm thinking that it has to be an issue with the signal getting back to the ECU.


Two questions. were does the connector #12 go and what does the little circled C mean?

Jesus. Has no one ever looked at a wiring diagram or done any electrical work what soever?
 

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Discussion Starter · #12 · (Edited)
1.8L which is making this whole thing more difficult because I can't find specific service manuals for this car. 1997 also has a completely different evap system than RS/L in 1998.

And I also found this

It's were C goes which is puzzling because that the TPS sensor, (which I was also having problems with.
 

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Zombie Killer
02WRX to 04 STi to 98RS-EJ255
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How about a different angle....I never saw you mention trying a new gas cap.


I believe C with the circle means it goes to the B136 Connector to your ECM. But dont quote me...I'm still learning how to read the diagrams.
 

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Discussion Starter · #16 ·
How about a different angle....I never saw you mention trying a new gas cap.
I did that. My gas tank holds pressure just fine (which it didn't at the start of this 4 month long endeavor). I'm thinking this is know a wiring issue. That Throttle Position sensor looks like it's tried in with the low signal i'm getting. It can't be coincidence that I was getting a TPS code earlier in the car's life.
 

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Discussion Starter · #19 ·
So the code has now magically morfed into a P0453 code. EVAP Fuel pressure high circuit.So at first it was a low voltage signal, now it's a high voltage signal? None of this makes sense at all!
 

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Discussion Starter · #20 ·
So the car is now throwing 3 codes
the p1440
a p0452
and p0453

All these codes completely contradict each other and I have know Idea what is going on.
P0452 Fuel Tank Pressure Sensor Circuit Low Input
P0453 Fuel Tank Pressure Sensor Circuit Hi Input
 
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