code p0452

Question

Have changed f pump done know what todo next

Answer 1

P0452 Evaporative system pressure sensor circuit low

This is for the (FTP) fuel tank pressure sensor, for this type of code you need to measure the referrence voltage to the FTP if the FTP referrence voltage is lower than 4.0 volts this is a ECM issue,

Comments

This does not match my wire colors

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Measure one of the wire, for a 5 volt with key on, this would be the reference voltage, as long as it is there you can move in another direction, P0452 you want to rule out reference voltage as being low, On the Forenza the EVAP hose once they get mixed it set a P0452. Do the measurement then you proceed to another direction.

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Here is what i have diagnosed so far :

CONNECTOR UNPLUGGED,


1.) I have continutity on the ground wire(black)
   
With KOEO
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2.) 5Volt Reference(Gray) - tested 4.99V
3.) Signal Wire(Dark Green) - jumped 5Vref to signal and backprobed at signal wire. Test showed 4.99v proving no connector fault.

CONNECTOR PLUGGED BACK IN,
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4.) FTPS test - removed FTPS from Fuel Pump and applied -10kpa vacuum on the sensor and it ranged from 1.3v - 4.74v
After releasing the vacuum pressure signal voltage returns to 1.3v ,,,,Did test 2 or 3 times to verify.

5.) Purge Valve - removed from car and applied voltage to test valve open close operation while applying vacuum on intake side. Valve opens and vacuum releases. Reinstalled and listened to the valve during purge duty cycle with stethoscope and valve was rattling away. Removed purge vent line to canister while car was running and engine vacuum was evident. Tested ECM driver with Test light on control wire and it was pulsing on/off.  

6.) Vent valve - A.)removed from car and applied voltage to test valve open close operation while blowing thru it - Valve closes.
KOEO: Connector Connected :
** Feed wire is 12v
** Control is 12v before closing the valve with scan tool.
** Commanded valve closed with scan tool while backprobing control wire with DMM and the voltage dropped

7.) Gas cap is brand new.

8.) The Drive Test Diagnosis - The MIL IS ON !!!......
After resetting MIL and now 93km later the "Evap Drive Cycle Monitor" is complete and "DTC P0452 is confirmed

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. At very low load The signal was perfect (1.4V-3.1V). During purge duty cycles voltage is higher 2-3v and doesn't seem to drop I am almost sure that the code is being set when there is positive pressure in tank, because freeze frame data was always indicating PURGE % = 0. But there was 1 time just recently when it was 99% and this totally confused me.

In order for the MIL to set the FTPS votage has to be less than ".1 Volts". I think is this has to happen on 2 consecutive trips for the DTC to come back on and my testing confirmed that.


So i have also done the following,
Commanded the Vent valve closed with my scanner and applied .5 psi shop air from the evap hose before the purge valve. Everthing seemed to hold pressure as i had a balloon attached to the Vent Solenoid end of EVAP system and waited 10 minutes. Came back and the balloon was still holding all pressure, so it seems that i have no leaks, thus no leak codes!!


PLEASE ADVISE,  I dont have a wiring diagram showing the FTPS circuit nor do i have a pin connector layout of the ECM to do a short / open testing on the REF & signal wires.

If anyone has the FTPS wiring diagram and ECM pin layout i would be forever grateful as i cannot find them anywhere on the WWW.

Whats really puzzling is that I have a 2004 Optra Service Manual but it doesn't show any information regarding the FTPS

The wire colors are 5vref=Gray, Signal=DK Green, Ground=Black/Wht

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If the purge valve is just slightly open you can set a P0452 without setting a lean code, the fuel trim would show it, with the short term and long term together as +7, The reason I say this I replaced the FTP only to have the code reset, and looking at the fuel trim that was the problem The purge was the problem all along the way