Hey guys I have an issue on my 2004 f350 6.0 that I am pretty stumped on.

I had a code for a bad EGR valve. Pulled the sensor and it was pretty dirty. I replaced the valve with a cheap $50.00 one off of Amazon. It ran okay for about 15 miles until I got into it. When I put a good load on the engine, it would cut fuel and go into a quick "limp mode." I was driving fine and it started to do this again so I pulled over and unplugged the valve. The truck revved up, revved down, revved up, (to about 1500 RPM if I were to guess) then shut off.

I was and still am locked out of the OBDII port and have not been able to get anything really. I checked fuses and nothing was popped. There was still a no crank no start, so I continued to look. I inspected the wiring harness and there are some exposed wires. I messed around with this and got the injectors to "buzz" for maybe two seconds then it stopped.

I ended up going to the PCM and unplugging each harness to rule out or determine if there was a short. Still nothing and no connection with the OBDII. I am not sure where I should go next. I know some other things create a no start but I am figuring it is related to the EGR valve or stemmed from that.

I also bought a new FoMoCo sensor and it did not change anything. Maybe it will once I can reconnect with the PCM?

Any help would be greatly appreciated!

 

Will the starter crank when you jumper the starter solenoid wire to the passenger side battery (+) terminal?

Do you have 12V power to the cigarette lighter plug in the cab?

Check for frayed or chafed wires around the fan clutch connector, the EGR connector, IPR connector, and the GPCM connectors.

Does your fuel pump come on with the key to "on"? You can best verify this by removing the secondary fuel filter, removing the standing fuel (or most of it), and then BRIEFLY turning the key to on to fill up the filter housing (it will fill in a few seconds).

Turn your key to on, put the shift lever to reverse, and verify that the reverse lights come on.

 

The starter will crank when I jumped the starter.

I believe I had 12V at the cig lighter, but can confirm tonight.

I have chaffed wire on the EGR Valve, they are all missing insulation in the same place. It looks like the plug was replaced but done in a ****ty job. I also separated all the wires so they weren't touching but this did not change anything. Wouldn't I see if there was a short by unplugging at the PCM. Fan clutch wiring looking good and I had voltage at the plug.

I do not believe the fuel pump comes on as I do not hear anything.

I can check the reverse lights tonight but I would've figured to rule this out as I never had this issue till I messed with the EGR valve.

 

The reason for the checks and my questions is to see if the PCM is active in the cranking/starting process.

If the PCM power is being pulled down in any one of a variety of places, it can cause the PCM to NOT command the grounds that activate the starter and fuel pump.

The fan clutch wiring is one of the most common places for a short that interferes with cranking, but it can also be at the EGR valve, GPCM wiring, MAF, or even the IPR valve.

Many times fuse 2.22 is blown when there is a 12V short in the PCM power supply circuit, but you said you checked all the fuses.

 

Correct, I have check all the fuses. Do you think the chaffed wiring could still cause me to be locked out of the PCM? I do not understand why I would be locked out of OBDII.

Do you think it would stem from the cheap EGR valve then unplugging?

 

Chafed wires can most certainly result in the PCM not functioning, and a PCM not functioning will result in no data from the OBDII port.

Even a shorted out fan clutch (internal to the clutch) can affect the PCM operation.

You could have a chafed EGR wire that is hidden back in a bundle of wires also.

 

If I had a chaffed wire but unplugged the middle harness on the PCM, wouldn't this rule out the problem being a chaffed wire?

 

Are you familiar with the circuits that are in that middle PCM connector? SOME (maybe even most) engine sensors are wired into that connector, but not all.

Circuits on this middle connector are: Glow Plug communication, VGT power and control, IPR control (ground), FICM controls/communication, 5-V reference power sensors: EGR valve (position sensor), EBP, ICP, ECT, EOT. Disconnecting this connector will remove most 5-volt sensors from the electrical system, plus a few critical 12-V circuits (like VGT, CMP, CKP).

So - IF the PCM isn't processing information, directing communication, and issuing commands - then disconnecting the middle connector would ONLY help if there were a short circuit on one of the above listed circuits that was dragging power down.

The "left plug" provides PCM circuits that go to quite a few engine components also: MAF, MAP, APP, Baro, WIF, Fuel Pump relay control (ground), Starter relay control (ground), Brake Pedal switch, PCM Power Relay circuit. In fact, the 12V PCM power that can be "dragged down" by a short (eg - in the fan clutch, EGR valve actuator 12v power supply, IPR 12-V power supply, GPCM 12V control power, MAF, etc) all tie into this left plug - the same plug that activates a ground to initiate the starter operation and fuel pump operation.

 

Thank you for this information, I was under the assumption those wires went back to the middle plug.

Is there a proper way to test this to see if there is a short in one of these other circuits (checking continuity in a plug, etc.)?

 

I think it is easier to see if the PCM is functioning first - fuel pump operation (confirm it is or isn't - don't guess or assume either way); AND reverse light function.

A failed transmission range sensor can keep the engine from cranking (but NOT prevent the fuel pump from functioning). You can potentially see that issue with the reverse light test.

 

I will check this when I go home.

What is the next step if transmission range sensor is bad? (Will lights come on if it's good?)

What is the next step if the fuel pump comes on or does not come on?

 

I would also recommend you checking for 12V power at pin #16 of the OBDII port. This is somewhat redundant to the check for power at the cigarette lighter plug.

These verify that the 12V power is available TO the PCM power relay. Power to the fuel pump and the reversing lights will show that power FROM the PCM relay is good, and proper operation of these relays at "Key ON" should provide initial verification that the Ignition Switch is functioning (at least partially), and the PCM is functioning at least partially.

Then you can verify the voltage at the red wires (circuit 361) at PCM connector C1381a (left plug) at pins 34 and 36. This outlines the circuit that provides the PCM power from Fuse 2.22 that comes from the PCM Power relay. Power To/From the PCM Power relay is available when the ignition is put in RUN or START.

PCM power at C1381a, pins 34 and 46, come from the same power source that feeds the following:
EGR valve actuator pin E
IPR pin A
GPCM connector C-1273b pin 9
Fan Clutch connector C1158 pin 5
MAF sensor connector C128, pin 2

note: - I corrected a typo above. originally I listed pins 34 and 36, but intended to list pins 34 and 46.

IMO, you should troubleshoot in a step-wise fashion ............ don't get ahead of yourself thinking about all the "what-ifs".

Afterall - the no-crank might be an issue with the wiring from the starter relay to the starter solenoid. Having two problems (no OBDII data) at the same time isn't all that uncommon.

 

You asked if the reversing lights will come on if the transmission range sensor is OK.

Answer - the reversing lights WILL come on if the following are good:

• Transmission Range Sensor
• PCM
• PCM Power Relay
• Reversing Light Relay
• Reversing light bulbs
• Wiring/Power to and from the above components involved in the circuit(s)

 

I checked to see if the reverse lights came on and got nothing. Didn’t have time to check if the fuel pump came on but I didn’t hear it.

Please note: I checked my PCM relay and it was fine when I checked it. Also clicks when I turn the key to start the truck.

 

Do you happen to have a diagram of the pins at the C1381a?