Torque

Forums

Forums

Guest  

Show or hide header
Welcome Guest, posting in this forum require registration.




Torque » Torque OBD ECU Scanner » Torque Discussion / Ideas » FTPressure is wrong!

Pages: [1]
Author Topic: FTPressure is wrong!
Amtp1
Member
Posts: 4
Post FTPressure is wrong!
on: February 15, 2018 (GMT)

I have a 04 f150 and it is throwing a P0451 code. It is suppose to be the tank pressure sensor. I started Torque pro and tried reading the pressure on the pid. On the manage custom pid page it says it is pid:221639 and the max/min is suppose to be 10.0/0.0. When I read it, the pid says the pressure is 4507PSI! The Equation shown is :((A*256)+B)*0.1449 . Is the Equation wrong or why is it reading sooooo far off. I have 2 Bluetooth adapters I have tried. 1 does not read this pid at all, and the other that has the Torque drawing and name on it that reads the wrong number. Any help will be appreciated. Do I need a different adapter (suggestions)? I hope someone will chime in before I have to drop the tank and purchase a sensor that might not be the problem. When I pull the cap off the tank when it is cold and pressurized by the ecu, the pid did change but I did not catch the number changes at the time. Thanks in advance for any help or suggestions.
Don

Capp777
Member
Posts: 2861
Post Re: FTPressure is wrong!
on: February 15, 2018 (GMT)

A quick web search of “221639 ford pid”
yielded an F150 site with a different
definition…

Units: Pa
Equation: ((Signed(A)*256)+B)
Min: -10000
Max: 1000

Units: kPa
Equation: ((Signed(A)*256)+B)*(1/1000)
Min: -10.0
Max: 1.0

Might be worth a try but not sure whose
definition is correct. (Added *256 which
was missing?)

F-150Torqued
Member
Posts: 427
Post Re: FTPressure is wrong!
on: February 15, 2018 (GMT)

@Capp777

The information you gave the OP is CORRECT — _BUT FORD MOVED THE PID_ on you -Darn them!. The Formula in the Torque Pro extended PIDs are not correct (((( FOR THE 2004 FORD F150 Lariat – at least)))). I have well learned that PIDs are NOT STANDARDIZED, even across different models of like brands, let alone universal.

I have gone crazy trying to sort out FTP on my 2004 Ford Truck. This is what I have learned. It seems that FORD ‘changed’ PID # 1639 from an OBDII ‘output’ reading FTP in Pascals as derived from the Fuel Tank pressure sensor voltage (which may NOT have previously been represented on OBDII at all — IDK). NOW PID 1639 is true Fuel Tank Pressure volts – unsigned 0 to 65535, I think in A/D counts, in some binary increment, perhaps 4 counts each A/D unit. ???

But, PID #1639 NOW shows Fuel Tank Pressure volts. The following formula produces an accurate reading as can be checked with a VOM on PIN ’44’ (20ga, Rd/Pk wire) at the 70 Pin Power Train Control Module plug.

PID # 1639

221639, Fuel Tank Pressure volts, FTPv, (A*256+B)/13107

——————–

The previous FTP ‘Output’ in Pascals was moved to PID # 1687. Apparently from the fuel tank pressure volts input – the PCM calculates fuel tank pressure into (the fine resolution) of Pascals. It can be positive OR negative because either “+” pressure builds up in the tank from the fuel vapors (if sealed and the carbon canister is somewhat clogged), or negative when the EVAP purge valve is modulated open to build manifold vacuum in the tank for EVAP tests. Normal readings are from ~ +50 to +100 Pa down to ~ negative 8000 – 9000 /// (perhaps 10,000 Pa if air cannot be draw air into the tank during EVAP tests through the normally open Evaporative canister vent valve.

The calculated pressure in Pascals is output DIRECTLY on PID 1687.

221687, Fuel Tank Pressure in Pascals, FTP_Pa, Signed(A)*256+B

A more common scale (TO ME) is Inches of Water. So the following formula converts the OBDII Pascals output into inches of water. I set up two gauges to display FTP in BOTH values as follows.

221687, Fuel Tank Pressure InH2O, FTP_InH2O, (Signed(A)*256+B)*0.0040146307866177

NOTE: (DISCLAIMER). AS FAR AS I KNOW, THIS INFORMATION IS APPLICABLE TO ONLY 2004 FORD F150 (gas) – probably through 2008 FORD for sure. Outside of that, I have NO IDEA.

Happy Torqueing

————–

5371019

Amtp1
Member
Posts: 4
Post Re: FTPressure is wrong!
on: March 18, 2018 (GMT)

Thanks for the response. I put in the water and voltage formulas into the programs for the pins. The voltage starts at 2.4v and during the test after starting cold drops to 1.3v but the water pressure drops from .4 to .1 then straight to .9 then to .2 and back to .9. It does after a few time going from.9 to .1 drop to-.1 then back to .9 then drops to.1 again. The water jumps up and down without the voltage jumping! Any thoughts? I pulled the connector and got 5v on ref, 5v on signal and 0 on the ground . I was lucky nothing shorted out when quickly shorting the pins to try to see pin voltage change. I had the wrong pins! Anyway the 5v is still there and the voltage dropped back to 2.4 when plugged back in. Any suggestions on a new sensor as mine is the one in the vent line instead of the tank and only Ford has them for 305.00 instead of the tank unit for 105.00. The ones on eBay that look correct are for different Ford’s. Will any of them interchange? Thanks
Which connector on the is the 70 pin one where pin44 can be checked? Is there a picture of the connector that shows the pin out numbers? Thanks again.

F-150Torqued
Member
Posts: 427
Post Re: FTPressure is wrong!
on: March 18, 2018 (GMT)

Your FTP ‘voltage’ readings do not look too out of whack – according to the “Daignostic Reference Values Values” http://www.devoll.com/public/5-4L_3v_F150_diagnostics_reference_values.pdf

The PCM Plug layouts are shown on top. BUT Beware – it doesn’t indicate it but the drawing is ‘stupidy’ as viewed from inside the CAB, not from under the hood. Also, I question the PCM Pin (B65), as that is not what I determine from the Schematics!! http://www.devoll.com/public/f150-wiring-Engine-Performance-wiring-pgs1-to-6-of-6.pdf Appears to me to be on 58, (or 44 with ref voltage on 29).

Two other points. You may need to increase number of decimal places on your voltage gauge to 3 to get a better idea of what’s happening, and Inches of Water are ‘little bitty’ compared to Kpa.

——————-

54371019

Amtp1
Member
Posts: 4
Post Re: FTPressure is wrong!
on: March 26, 2018 (GMT)

Thanks for the pages. Can I ask where you got the diagrams from? I purchased Aldata trying to find information, but they are not as good as these seem to be. I am still trying to find the sensor as no one seems to have one.I went on ebay and they have one that looks like my inline sensor for a 7 and 8 ford explorer so I hope it will use the same voltages and return voltages that the one on my truck uses. You would think Ford would at least use a consistent set of values. If not, I will have to wait for someone to get them in.
Thanks again for your help.

F-150Torqued
Member
Posts: 427
Post Re: FTPressure is wrong!
on: March 27, 2018 (GMT)

@Amtp1, I have set up a temporary private email account for you on my mail server. F-150Torqued-Amtp1@devoll.com

If you will send your email address to me there, I will provide you some more good documentation that I have for our trucks.

———–

54371019

Pages: [1]
WP-Forum by: Fredrik Fahlstad, Version: 2.4
Page loaded in: 0.176 seconds.

  Follow me on twitter