F550 is dead on the road...Help!
 

Well the F550 just randomly shut off on the highway doing 120 km/h, and does not start back up. As of right now its in the shop getting fixed...anyone got an idea why it would just turn off with no warning? We did change the battery on Friday though.

120kmph sounds like 81 mph, which if you hit, will either immediatley shut off, or go into reduced power mode, if it's a 6.4. F450 and 550 have a speed limiter set at 81 mph. 250 and 350 are a little higher if I remember correctly.

I'm assuming you have a 6.4, since you posted in this forum?

Could very easily have been an EGT sensor that shut it down.

Or that, yea. Most likely he hit the speed limiter though. i'm not sure of a kmph to mph conversion, but is sounds awfully close.

this is where my money is at

hitting the speed limiter does not shut the truck down. It will just top out and stay there.

A sensor.

Yea its a 6.4. But 81 MPH is 130 KM/H, but the truck doesn't go farther than 140 KM/H. Doubt that it would just shut off if you hit the limiter though

So who wants to hear the terrible news? We got word today saying that the engine harness needs to be replaced. Not sure how they got to the conclusion but I will ask. Could the backup camera we installed have to do anything with this?

Wait what is an EGT sensor and what's its sole purpose?

Exaust Gas Temp sensor . Known failures causing shut down and no restart . Truck goes into " lock down " .

Senix, was there not a TSB on the engine wiring harness getting chaffed or was that another harness?

there was but don't have it right now. Will see if I can find it today

Here is what I was thinking...
TSB 07-26-2

12/24/07

6.4L - INTERMITTENT NO START / LACK OF
POWER - DTC P0003 AND/OR BLOWN FUSE 74 -
BUILT PRIOR - 8/20/2007

FORD:
2008 F-Super Duty

ISSUE
Some 2008 F-Super Duty vehicles built prior to 8/20/2007 equipped with a 6.4L diesel engine may exhibit a lack of power or no start with possible DTC\'s P0003, P0004 and P0091 caused by circuit CBB12 at the high pressure pump gasket grounding to the high pressure pump body (may also result in fuse 74 being blown).

ACTION
Follow the Service Procedure steps to correct the condition.

SERVICE PROCEDURE

1. Unplug connector C1926 near the high pressure fuel pump cover.

2. Check pin 4 green/white and pin 2 yellow wires for a short to ground.

a. If either one is shorted to ground, remove the high pressure fuel pump cover and replace the pump cover gasket/harness that contains the grounded wire ONLY [...]Click here for full access to all TSBs with our partner AllData

Like hell it won't. You want me to post the screen shot from my IDS showing the exact moment it happened? I also have a report form the GPS system isntalled on all our trucks that generates a report whenever a DTC is set, in this case, an overspeed code set at 81 mph.

Yes, an open or bad EGT sensor can and will shut the truck off immediatley, but you'll usually get a message on the instrument cluster telling you to pull over safely. You get about 3-5 seconds to do so before it shuts down.

there is an overspeed code. I have had it a few times. No shut down due to the overspeed. Just a defueling.