Help! Very low mpg –wrong PCM?
 

Hi, my truck, a 95 F150 351 4x4 E4OD runs 6-8mpg!<st1> Lot</st1> too much. I think 18-20mpg should be normal. The Engine runs smooth and has power. I check KOEO test and receive Code 113. I check’t all arts and harness but no error only the PCM has no voltage at pin 25 (IAT) and so the Handbook says PCM Change! It is possible that only a wrong IAT-Signal can increased the used fuel?<o> </o>

Here in <st1:country-region w:st="on"><st1>Germany</st1></st1:country-region> it is very hard to find somebody who can test or repair a PCM for Ford Trucks. In Ebay <st1:country-region w:st="on"><st1>USA</st1></st1:country-region> I couldn’t found a PCM/ECU F5TF-12A650-YB – that’s in and I don’t know if some other is compatible. Maybe somebody has an Idea how I can solve the Problem? The only chance for me is, to buy a used, working PCM in US.<o> </o>

I need the 4x4 Truck to serve my horses out in the dessert with hay and straw and I’m not so rich to spend a lot of money for Gas or new parts. In normal use a Ford 4x4 take’s more mpg then a German or Japanese 4x4 with enough Power for trailer towing.<o> </o>

For information: I bought this car for a very low price because a fire in the engineroom wrecked the harness and some parts and the old Owner could not find somebody to repair it. So I ordered a service CD from FORD US and rebuild the Harness and change all destroyed parts. By the way I found, that some “Spezialists” have change Parts and so I rebuild it by the original way! Maybe the PCM was wrong programmed? The Car has also a LPG Landi REnzo Venturi System in it, but this I will first check, if the Engine runs with normal mpg on Gas.<o></o>

Thanks for help<o></o>

Winfried from<st1> northern Germany</st1><o></o>

you are dreaming if you think you should get 18-20 mpg with your truck, more like 12-16 mpg.

You are right! I make a kalkulation mistake 12-16 mpg are ok. that means 13 -18 liters per 100km. But you are agree that 35 - 40 liters per 100km (6-8 mpg) is very taff and too mutch!?

In my manual, it says that a code 113 is
"ACT sensor circuit open or reads & minus;40<deg.>F.

According to Fordfuelinjection.com under "three digit self codes" it says
"ACT sensor signal is greater than the Self-Test maximum of 4.6 volts."

Either way, it sounds like your Air Charge Temperature sensor is bad, or the wires to that sensor still aren't replaced (from the fire).

This would definetly make your truck get bad gas milage, because the PCM is sensing that the engine is still cold, so it keeps sending it more fuel...... Check the sensor and the wires from it to the PCM and make sure that they aren't burned through and shorting somewhere...if they're not, check the sensor..If it's bad replace it and let us know how it goes!

Hi,
I think we are meaning the same -in my handbook it calls "IAT" Input Air Temperatur. The seensor is OK and within the specification (50k -1k). The wires are olso OK no short -no break but the pcm has no voltage at pin 25.That looks as in the pcm is an elektronic break. I will take the pcm out today and check it intern where the voltage will lost. there is also a second symtom: if it rains and i drive with headlights ,the E4OD starts to shutter and the OD-light starts to flash. if is is dry and without light the E4OD runs smoth.
but thanks for the idea.

Not sure what you are measuring with but you need very high impedance DVM to measure this voltage at pin #25.
With the IAT sensor disconnected you should get 4.6 Volts DC at pin#25 providing you measure 5 Volts Reference voltage at the TPS connector with it unplugged.
Normal range of voltage at pin #25 is from 0.27 Volts (@ 120 deg Celsius, 1.18 K ohms) to 3.51 Volts (@ 10 deg Celsius, 58.75 K ohms).

Here is a diagram of the input.
http://i54.photobucket.com/albums/g9...M/IATInput.gif

i use a high impedance DVM and an oszylloscope. today i remove the pcm and check it out of the car in a test circut: all voltage are ok also 4,6v on pin 25 (by the way thanks for the grafic) the i pluged the pcm on an test all values direct in the pcm. Everything working well. After the complete installation of the PCM it looks good. The Testdrive work the first 5 miles fine the I went out in the dessert and after the first shackin - the MIL was lighting! Then I shake the harness on the PCM connector and the sound change. I have the suspicion, that the sockets inside the connector are oxydated ore to wide from to many changes. next step i will open the connector and change all socket with new one and see what goes on.
the problem with the shutteling of the gears i also locate but no understand. Without headlights the E4OD runs well but if i make on the light, the gears change down and change very hard over 2500rpm.

fire can do wonders to the underhood of a vehicle. Sounds like maybe a melted short somewhere?

fix one -find another Problem
 

yea, fire do woder! I check and open the PCM Connector (C185) ans find 11 brocken or corroded contacts what you cant see from outside. Also are 2 wires inside the HO2S sensor brocken - i bourght a new one. The first runs look ok. no new error codes only 111. Hope that now mpg will be better.

But I cant find the error in the tranny. When ever I switch on the headlight, the tranny wouldt shift below 2700 rpm and then very hard and OD-light starts to flash! Do I change from low to high beam - everything get normal!
any Idea?

The only place the wires come close together is in the Instrument cluster for the high beam indicator and PSOM. I would check there and make sure there is a good ground for the Instrument cluster. Sounds like the ground for the PSOM is bad.

Does the speedometer quit when you put on the high beams also?

thanks subfort. It's a good idea! I think also that it must in the instrument cluster. Tomorrow I will check it maybe I make a mistake by change the wire for brake- and foglight behind the instrument cluster for german law (Brakelight must work seperate from Turnlight).
The Speedometer runs well, but maybe it has to do with the error code 452, that sometimes came up.

Yes the error code 452 could be the problem.
Here is part of what the book says on the 452.

Continuous Memory DTC 452 indicates the PCM detected an error in the PSOM output signal during the last 40 warm-up cycles.

Possible Causes:
Damaged Rear Anti-Lock Brake Sensor.
Damaged PSOM.
Damaged harness circuits.
Damaged Powertrain Control Module (PCM).

Key off.
Disconnect Powertrain Control Module (PCM). Inspect for damaged or pushed out pins, corrosion, loose wires, etc. Service as necessary.
Install breakout box, leave PCM disconnected.
Measure resistance between Test Pin 3 and Test Pin 6 at the breakout box.
Is resistance between 21,000 and 55,000 ohms?

sorry for the long delay but I do a lot off work: I have check all connectors of brocken contacts, test wire by wire for a short to ground - vbat or together, had make all the test of the service manual (original Ford CD for 95 Pickup and Vans) and rebuild the harness back to original, include sensors. Also i test the complete fuel system for leakage.The result: no more error codes and the knowlegde - not fire wors wonder - all the Speciatists who ever wort on this car! A lot of wrong sensors, cutted wires, new wires (for what ever), self made excaust system and more. I think, this car has never seen a tecnican with ford experiance or a service manual on side.
So in the next step i check't the axle ID, Gear ration and tire size with the Car ID Plate inside the drivers dor, but this things are locking good. Only the Excaust system are not loocking shure.
Is it correct that the pipe into the 2end Cat has 3' and the output only 2 1/4'??

After the happines over no error codes came the frustration after the 50 mile testdrive: 6mpg!!! If something working wrong like HO2 or EGR I understand a increase of gas for 20% to maybe 40% but not 100% to 130%!

The Engine runs very smoth in all ranges, no no extrem Gas smell - I'm now to be at one's wits' end.

Eny Ideas??????????????

just a question, but are they stock tires on that truck? if they're a different size, the speedometer and odometer will be off, giving faulty readings.

the certification label notes "P265/75 R15" but 275/60 R15 ate mounted.
Why are the Speedometer and odometer off, if different tires are mounted? And can this increase the fuel so dramaticly?