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Author Topic: 04 F150 PIDs list with formulas/ evap pressure issues
Amtp1
Member
Posts: 4
 04 F150 PIDs list with formulas/ evap pressure issueson: August 2, 2018 (GMT)

I was wondering if there is a complete list of pids for my 04 f150 with a 5.4l? I was trying to check the evap system as I have a P0451 code that says the FTP sensor is not reading correctly. I have Torque set to read the pascals, water pressure vacuum, and supply the voltage. The voltage reads low and with the smoke machine on it changes upwards to about 2.6 Volts but the pascals are -1800 and the water reads .5 inches when I have 7 inches of water pressure. Only the voltage changes about 1/2 a volt. My formulas must be wrong. Any help will be appreciated.

Capp777
Member
Posts: 2978
 Re: 04 F150 PIDs list with formulas/ evap pressure issueson: August 2, 2018 (GMT)

What pid data are you using to read Fuel
Tank Pressure?

My notes suggest the base units are in
inches of water?

Torque’s predefined pid looks like
voltage scaled to psi?

F-150Torqued
Member
Posts: 437
 Re: 04 F150 PIDs list with formulas/ evap pressure issueson: August 4, 2018 (GMT)

It seems to me that – at some point in time, (or in certain Models), Ford switched PID assignment between FTP and FTPS_V. For sure in the 2004 F150 5.4L, FTP as calculated by the PCM and posted at PID 1687 in “+” and “-” Pascals between ~ +200 to -8,500. Formula for direct reading in Pa is Signed(A)*256+B. PID 1687 can be converted from ‘Pa’ into In-H20 (or setup a separate gauge) by using the formula (Signed(A)*256+B)*0.004146307866177 for reading In-H20 between ~ +5 to -30. The evap system generally maintains negative pressure in the fuel tank all the time, by periodically modulating the Evap Purge valve open slightly. This is to prevent fuel vapors from escaping into the atmosphere through the Normally Open Carbon Canister vent valve. The exception to this is during certain OBDII evap monitor tests. ie: vapor generation, or for checking for what is called ‘in-flight’ refueling and so forth.

PID # 1639 is Fuel Tank Pressure Sensor Volts – A/D convertor count scaled from Zero to 65535. Formula = (A*256+B)/13107. Not sure how many steps the A/D converter resistor ladder has – but 13107 scales the PID reading from Zero to Five volts in plenty fine resolution. The sensor is biased to nominal ~2.5 volts – midscale- at ZERO tank pressure (atmospheric, or gas cap off). Apparently the PCM ‘re-calibrates’ itself at KEY ON after sufficient engine soak. It seems Zero pressure can occur at different voltages roughly from ~ 2.4 to 2.6 volts. But what is important is amount of increase or decrease from the base voltage established at KOEO after some ?? soak time. On my vehicle, FTPS_V reads very close to 2.5 KOEO, maximum Evap Purge Valve current (wide open) will draw tank pressure volts down to around 1.2 volts and read around – 6000 Pa.

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54371019

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