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