2006 CHEVY OPTRA (P0454, THEN P0452)

[CanAm58]

Hello,
Below is the tests i have performed on the FTPS problem so far. I am a DIY'er and seem to have hit a block in the road
I have no wiring diagram for this cars FTPS circuit as i cannot find one. I have a service manual for a 2004 Optra and it doesn't list anything for the FTPS circuit.
NOTE: I do not have a Fancy dancy scanner with square waves etc. I only have a simple Actron scanner CP9580a and a DMM.

Here is what i have diagnosed so far:

Connector Unplugged,

With Key off
-------------
1.) I have continutity on the ground wire(black)

With Key on Engine off
-----------------------
2.) 5Volt Reference - tested 4.99V on the reference wire (gray)
3.) Signal Wire - jumped 5Vref to signal and backprobed the signal wire (ecm side of connector). Test showed 4.99v proving no connector fault.

CONNECTOR PLUGGED BACK IN,

4.) FTPS test - removed FTPS from Fuel Tank Pump assembly and applied -10kpa vacuum on the sensor and it ranged from 1.3v - 4.74v
After releasing the vacuum pressure voltage returns to starting point. (1.4v or 4.94) cant remember which was the starting point.
did this a few times to confirm that sensor fluctuated within this range...so seems to be working.

5.) Purge Valve - removed from car and applied voltage to test valve open close operation while applying vacuum - Valve opens
Also listened to the purge cycle with mechanic stethascope and valve was rattling away (while car running).

6.) Vent valve - removed from car and applied voltage to test valve open close operation while blowing thru it - Valve closes.

7.) Gas cap is brand new.

8.) The Drive Test Diagnosis - The MIL is on - "P0454 only" after resetting MIL and now 93km later i still haven't gotten the P0452 to reappear yet, but it will as i have done this many time already. With the DMM connected to ground and backprobed to the signal wire on connector (ecm side) i observed the Voltage reading while driving for 15 minutes. In City and on Highway the signal was perfect (1.4V-3.1V).
Went home let car cool and retested. Drove same distance never tromping on throttle. Stopped, waited a few minutes and restarted car and the MIL went off (expected). All the drive time the FTPS signal Voltage was perfect.

SO I APPLIED SOME FORCE TO HER ON THE NEXT TRIP FLOORING THE GAS PEDAL WHILE OBSERVING THE DMM VOLTAGE and sure enough the voltage dropped below threshhold and went haywire at times. (leading me to beleive the the sensor if faulty). This resulted in the MIL coming back on IMMEDIATELY after the second attempt.

Not sure what caused the FTPS to go haywire/eratic and go below .1 Volts (i think thats the threshhold which has to happen on 2 consecutive trips for the MIL to come on?).

But i have reservations about going out and replacing the sensor (throwing money at parts) until am absolutely sure about the fix.
I did close vent valve with my scanner and applied .5 psi shop air from the evap hose before the purge valve. Everthing seemed to hold pressure but i have no way of determining this as I dont have a fancy smoke machine with pressure gage). I do have a MityVac Vacuum pump which does both pressure and vacuum. I tryed to apply vacuum to the line at first but it didnt seems to be strong enough to pull vacuum or i may have not closed the vent valve (cant remember) I will try this again.


As mentioned I dont want to throw money at parts until 100% sure of fix.
PLEASE ADVISE, AS I AM NOT SURE WHICH FORK IN THE ROAD TO TAKE FOR THE NEXT STEP.

[carriedi]

The Chevy Optra is not sold in the US. So, I don't have direct information on the vehicle, however, it is supposed to be the Suzuki Forenza here is the US. so for that I do have a wiring diagram of the ftps circuit. It looks like there isn't a lot of things that can can be the cause of the P0454 code. Bad sensor, bad connection or wiring, bad module.

the ftps contains an internal amplifier circuit that needs the correct voltage in order for it to work correctly. If you can drive the vehicle while monitoring the 5 volt reference signal and the 5v remains constant when the signal return acts erradic then it can only ba a bad sensor or a poor ground. Since the ground for the ftps is the same as the fuel level sensor and you don't have a code for the fuel level sensor, you're narrowing the connection to between the ftps and the fuel level sensor. and while that is possible, it is would be more likely to be a bad sensor.

[CanAm58]

Thanks Carriedi !!!

Well still stumped after replacing the FTPS. Same problem. Been doing so much research and everything is pointing to TOO MUCH (Positive)PRESSURE BUILDUP IN THE TANK. I have read that the tank vent hose connected to the canister could get clogged or the canister could be saturated drowning the end of the pipe. OK so i removed the FTPS and blew shop air threw FTPS hole in tank. Air made its way to the Vent Solenoid Valve where i attached a balloon. (This is great way to pressure test EVAP system for pressure holding ability without a smoke machine). Have also blown air from purge side to vent side therefore - "every line in the evap system holds pressure and every line passes shop air" , except for exiting the gas tank filler hole (i dont think its suppose to be able to vent cause of a one way valve in the tank correct me if i am wrong).......so I am again stumped. I have checked everything i can and still no fix. WTHeck!

I guess i'm going to have to disconnect the ECM and run an Ohms test on the ground wire, signal wire, and 5V ref.
Do you have a pin connector layout for the ECM connectors ?
That would make my day.

I will also be checking the ground wire between the ftps and fuel pump according to circuit diagram (thanks again!)

Again, thank you for your time and helping in the matter.

[carriedi]

ok, the voltage reading you should have with the gas cap removed is 2.35 to 2.85 volts. That should be your starting point