2004 F350 6.0 (ICP is behind turbo)



I got this truck from my great aunt about 6 months ago. Around 2021, it was stolen and got stuck in the mud before it was pulled out by crane. I was told the truck ran for some time after this incident but recently it was left sitting for about 3 years.

I drained and checked the oil. Confirmed it was just old with no fuel or contaminants. Dropped and cleaned the tank, added 15 gallons of fresh diesel. Added new OEM air filter, fuel filter and oil filter with new OEM caps. Replaced the damaged ignition. Replaced starter, Air Filter Intake gauge, 2 new batteries. Replaced a few fuses and starter relay too.


When key it turned to on, my dash lights up but I get no fuel pump sound or fuel to filter. No FICM, or clicks of relays too, but there is a faint grumble sound of something for one second, maybe vacuum? The scanner is unable to communicate with the ECU.



When key is turned to start, I get no starter action or anything, just the gauges on the dash and a beep. Jumping the starter only spins it in place, the solenoid doesn’t engage. I ran a wire to test the main starter cable and results are the same.



When attempting to start the truck in neutral, the reverse lights do not turn on and there is no change with the starter, relays, fuel pump or anything.



I’m getting 12V power to the cigarette lighter and to pin 16 on the OBDII port, which tells me the PCM has power in; but the PCM is not commanding the starter or fuel pump on. At fuse 22 I get 1.5V with the key on or off. If I put 12V to this circuit, I hear the fuel pump engage but still nothing from the starter when I turn the key to start. I tested the PCM plug C1381a (left plug closest to firewall) at pins 34 and 46 and I’m only seeing about 1.2Vs each at both of these pins. Tested at pin 21 of C1385 and it only has .8Vs when key is in the on position.



Things tested:

Disconnected first and second PCM connects(mostly engine sensors) and tested, no change with the starter, relays, fuel pump or anything.



Just to be sure, I went through and individually checked the fan clutch, EGR, TRS, GPCM, MAS, VGT, ICP, and EPB connectors/wiring. Then tested again by unplugging each one but still no fuel pump and no crack when key is in on.



Tested at the large external connector on the transmission(pin 21 of C1385). It only has about .8Vs at pin 21 on C1385 when key is in the on position.



At fuse 22 in the cabin fuse box, I get 1.5V with the key on or off. If I put 12V to this fuse, I hear the fuel pump but still nothing from starter when I turn the key.



Then tested the voltage at circuit 361 - PCM connector C1381a (left plug) at pins 34 and 46. I am only seeing about 1.2Vs at both of these.



I don’t think it’s a shorted out TRS and/or wiring internal to the transmission because testing with C1385 unplugged got me nowhere.



Is it a bad PCM? Am I missing something else that could be pulling power down from the PCM? I’m at a bit of a loss of where I should take it from here. Any and all advice, guidance or recommendations will be greatly appreciated. Thank you.

 

did you already try a 2nd pcm but did not fix maybe i misinterpreted the post


Did I miss something
Did you test pcm power relay ?

Battery cables and grounds clean

If I remember correct a CJB can malfunction inside circuits is that the issue Idk more testing probably required

 

Thank you for taking the time to review and provide some input. I have not been able to test a know working PCM unfortunately.

I tested both sides (12V) and the ground for the PCM power relay, as well as swapped in a working relay. When I put power to the ground on the PCM relay to simulate the relay engaged, I still do not hear anything else click. This told me that no matter, the PCM is not commanding even with power in.

Battery cables, terminal connections and ground connections are for sure good as I see 12V into PCM and other testing circuits into PCM.

I will look into the CJB malfunction and see if I can isolate the circuit and maybe test the resistance.

 

Random question, but SHOULD the gauges sweep when you first go to KOEO? I don't have my 03 in front of me to check.

Where you at in Texas buddy?

 

I’m not sure if they should, but the gauges do sweep when first going to KOEO.

I’m located in San Antonio.

 

I tested each circuit on the CJB and can see power to the critical fuses. (Should I test anything specific?)

After some research on CJB failures, it’s usually the fuel pump relay or half the board takes a dump. I’m getting power to the PCM but somewhere, the power is being pulled down keeping it from commanding the relays on.

 

I don't know if you have a wiring diagram, but here is a link.

https://charm.li/Ford/2004/F%20350%2...0Diagram/26-1/

This is a website with all the diagrams so you can back navigate for more information.

Check all the power inputs to the PCM. Note there is Vbatt and Vpwr. Check the diode on the power relay. It is there to protect the PCM from Vpwr if the battery is connected backwards.

 

Thank you for providing that diagram Don. I did check power at the PCM relay and tried to jump it but it has no effect. I will look over the diagram more and test the Vbatts and Vpwr circuits.

I can’t recall there being a diode on the PCM power relay but will pull it and verify.

 

I’m getting power into the PCM as pins 86 and 30 of the PCM relay are showing 12V. But testing the voltage going out of the PCM at circuit 361 - PCM connector C1381a (left plug) at pins 34 and 46, I am only seeing about 1.2Vs at both of these.

Does this tell me the PCM is bad or could voltage still be drawn down from another source? I also tested by disconnecting two of the three main PCM plugs as well as each sensor but still nothing.

 

The PCM gets VPWR through the relay. If you verified the fuse after the relay, F2.22, 20 amp, is good then power is either being lost in a broken wire or pulled down by the PCM circuitry (I don't know how/why it would do this). This VPWR circuit power also runs the IPR (see Dwg 26-6 arrow "C"). So the task is to find out why VPWR source is not working. Note there is a ciritcal splice, S123, where multiple VPWR wires are connected. I have no idea where it is located in the wire loom...but this manual can identify the location if we need it.

The relay is turned on by the ignition switch in "run" or "start".

 

Gauge should only sweep one time at KOEO after battery unhooked and KAM reset

Gauge should Not sweep Every time @ KOEO

 

I see, I would chalk this up to the PCM power draw

 

I see, I would chalk this up to the PCM power draw

 

I disconnected the IPR to test and still do not get power from PCM. It looks clean with no issues and the wires do not appear damaged. 151k truck, original everything so not much has been messed with underneath the hood.

I also disconnect C2 and C3 from the PCM to see if communications started working to the DLC in an attempt to test all the other sensors on that 361 circuit with no results.

I’m going through Bismic’s Troubleshooting - OBDII port (DLC connector) does not connect to scan tool or to tuner (no communication) guide and a few older posts on this issue to see where I can get.

Thanks yall, I really appreciate the help so far. It’s also motivating me to get back working on the truck.

 

I'm in Ft Worth, if you were here I'd let you come grab a PCM out of my trucks but I can't get it down to you, sorry. There are a few shops that rebuild them, might be worth sending it out while you're hunting down wires.