U1800?????

U1800?????


Code: U1800
Modules:
Description: Lost Communications With Fuel Injector Control Module (FICM)

Is that the DTC you getting?

Check Fuses first, then relay

Which Relay?

Maybe one the Techs on here can help ya locate the right one.....I know there are several

where is the ficm relay located?
thx
Vernon

This is probably the best explanation of the FICM that I have seen....

Too bad he compares it to Ford..

Ford’s first-generation Power Stroke fuel pump used a two-stage fuel pump to bring the fuel from the tank to the engine and then pressurize it around 50 psi for delivery to the injectors. In comparison, the Duramax also uses a two-stage fuel pump, but rather than utilizing a diaphragm-type pump for lift, a pair of spur gears is used to bring fuel from the supply. The spur gear pump creates about 5 inches of vacuum to draw fuel from the tank, where it first passes under the Fuel Injector Control Module (FICM). The FICM is a neatly boxed array of step-up transformers and electronics similar to the Power Stroke’sInjector Driver Module.
The reason the fuel passes under the FICM is to keep the module cool. Then it is drawn through a heater-equipped filter/separator, which has a priming pump and a bleed screw, before reaching the two-stage fuel pump. The spur gears feed the fuel into the high-pressure side of the pump, which is a radial design with three pistons set 120 degrees apart. This camshaft-driven pump only consumes a fraction of the torque necessary to drive a normal injector pump and is capable of producing nearly 30,000 psi of fuel pressure. The pump pressure obviously must be regulated, and for safety purposes, the Bosch folks designed a pop-off valve that feeds excess pressure back into the return side of the system.

I believe this is due to the ecm not communicating properly with the FICM via a serial interface. I also believe that the TCM is on this same serial interface.

I was getting that exact code plus another that is for losing comm with the TCM which would then reset all my taps and the trans would shift hard.

I never quite found the problem but I went into to the wire bundle to trace out the lines...routed as twisted pair and terminated in 120ohms differential at the FICM(if i remember correctly).

AFter ohming everything out and reconnecting I never got the codes again.

I did have a service manuel that called out the signals at the connectors etc which is needed in finding the lines and troubleshooting.

Since you are not getting the tcm loss of comm code then it might be something with the FICM and not the actual connection...just me guessing here.

If anything try ohming out the differential input at the FICM to verify you get around 120ohms.

10-4
Thx A Million

Where Is The Tcm Located?

The TCM is located near the front on the passenger side for the 2004 LB7's ....I think all the LB7's are there. Also nearby is the ECM. The wiring gets over to the FICM via the wiring harness through some connector blocks, over the top of the engine then to the FICM.

Good luck.

Its Running!!!!!!!!!!!!!!!!!!!!!!!!

Dont Ask!!!!!!!!!!!!!!!!!


It Just Runs!!!!!!!!!!!!!!!!!!

Sounds like an intermittent connection

Great news thou

Just because you said "Don't ask", I'm gonna...what was it man...inquiring minds need to know.....:D

YESTERDAY I INSTALLED ORIGINAL FICM,NO START
WENT TODAY, UNPLUGGED/PLUGGED TCM,PRIMED FUEL SYSTEM LIKE 100xS
STARTED UP, SHOCKED
SO DUNNO IF IT WAS THE THE TCM OR WHAT FOR SURE JUST A GUESS

I STILL THINK ORIGINAL FICM IS BAD,JUST A GLICH

YESTERDAY I INSTALLED ORIGINAL FICM,NO START
WENT TODAY, UNPLUGGED/PLUGGED TCM,PRIMED FUEL SYSTEM LIKE 100xS
STARTED UP, SHOCKED
SO DUNNO IF IT WAS THE THE TCM OR WHAT FOR SURE JUST A GUESS

I STILL THINK ORIGINAL FICM IS BAD,JUST A GLICH

Have you ever ran an Edge or Va box, if so recheck the bale connectors.

Most likely the problem is there with a loose connection...........;)

The Owner Advised He Ran Some A/m Program But Dunno The Brand

Guess the plug loosened up, eh?

Dunno
Guess I Did The Ford Wiggle Test

Dunno
Guess I Did The Ford Wiggle Test
:rolleyes: Priceless :muahaha:

X2

I have U1800 on an '03.
It starts OK, runs well, pulls trailer well, etc.
Autozone read it out for me, there were other codes indicating loss of communication with xyz I forgot exactly.

Anyway, another (possibly unrelated) symptom is that I have the orange low fuel light on all the time, the fuel gauge reads empty, even with 30 gallons on board, the 'Range' indicates a line of hyphens, but 'inst econ' reads about right. I have two tanks (3500 regular cab) and the transfer from rear to front seems to be normal, i.e. both tanks take on similar amounts when I fill up.
I've checked all the fuses, disconnected/re-connected everything under the hood that I reasonably could, Ford wiggled the relays - now out of ideas.

DANG this is weird.
If the batteries run flat the empty fuel alarm goes out and RANGE comes back to sanity. I know this because I "ran out of fuel" (not really, I'll explain later) and cranked my batteries flat trying to re-start it. Once the batteries came back up the yellow light came back on and the RANGE reverted to hyphens.
{Yeah, I know about the bleed screw on the top of the filter and I've changed the fuel filter a few times, so this isn't new to me.}

Ahh, back to that "ran out of fuel" I mentioned.
Since I have been without a fuel gage for a couple of weeks now I have been filling up both tanks every 500 miles, whether I need to or not. The Bus/Personal trip MPG calculation and trip miles have allowed me to do the arithmetic and when I have filled up both tanks the amount I have bought has been about right. So I've been ASSUMING that this is only a display level problem. HOWEVERRRrrrrrrrrrrrrrrrrr, it quit and my first reaction was that I must have run out of fuel despite the arithmetic that said I should have a dozen or more gallons left {1/4 or so of total capacity}. So I popped the hood and sure enough the primer was "soft". I put in the 5 gallons that I carry and the primer still didn't firm up after another 100 or so strokes. I opened the drain, warm fuel came out, a few more strokes and I opened the bleed screw on top, foam came out. It still wouldn't start and on the slim chance that I was sucking dregs from the front tank with only 5 gallons in it, I went and got another 5 gallons.
When it did eventually start after a lot of bleeding foam out the top I noticed that RANGE said 300 something miles. It ran OK to the first fuel station about 4 miles away and as I was looking at the volt meter trying to decide whether to turn it off the RANGE reverted to hyphens and the orange light came back. I had over 14 volts and decided to turn it off while refilling. The front tank took 15 gallons, about right for a tank that had been empty 4 miles ago and had 10 gallons put in it. The rear tank took only 11 gallons, so 26 total plus the 10 I put in 4 miles earlier says I had 14 or so in the rear tank and it wasn't getting pumped forwards.


I did about 350 more miles yesterday without incident.
This morning I decided to deliberately run the batteries down, first I checked that the fault was still there, yes. Then I put about 140 watts of trailer lights on - ta dahh, the fuel gage returned and the RANGE showed about 300 miles. I put the battery charger on it to sit and see if the fault returns when the battery voltage gets back up, but that was taking too long and I wasn't willing to go to 100 amp charge just to speed it up. Maybe I'll do that tomorrow.
Maybe I'll just drive it, but I didn't want to introduce movement or fuel flow into the experiment until I've established whether it is JUST battery voltage that affects it.

Any ideas would be much appreciated.

Weirder and weirder...
The Low fuel light, loss of fuel gauge and hyphens for RANGE symptom (all 3 together, ALWAYS together, no cases of only one or two) seem to occur
if the truck is left to idle for a while. This is something I do only very rarely, partly because I'm too cheap to to let it run just to keep warm. Then they clear (all 3 clear, not one or two) if I run the batteries down and get a jump.
They stay cleared for days/weeks, many of my drives have been 6 or 7 hours, so I know the voltage and battery charge are way up.

The only thing I know is different about driving vs idling in neutral is that the fuel cooler doesn't get any air flow, but I have a SERIOUS problem relating that to the symptoms. BTW, I tried disconnecting (BOTH) the batteries to see if that would re-set things, it didn't, I left them disconnected overnight, that didn't clear it either. It definitely needs LOW volts, not NO volts to re-set this set of symptoms.

Check your ground wires for corrosion.

Check your ground wires for corrosion.


Right;
WADR - the grounding system on these trucks is a friggin' MAZE !
but yes, I need to go through the schematic to find a ground path that would be indicted by this symptom set.
tnx,

\R