We are full timers and when we were towing our 5th wheel in September to a campground in N.C. my truck engine light went on and I lost power going up a hill. I was able to pull over and shut the truck down and restarted it and had no more issues. Later, my wrench light went on but the truck preformed normally. I did reset it once while overnight camping and after restarting the truck the light went on a second time. I drove to N.C. without resetting again and after I brought the truck to a Ford dealership, they got the code and traced the probable cause to a bad alternator. I have driven the truck without the 5er and the code has not returned. The truck has not been used often, and I have let the battery run down a bit. After starting I check the output to the batteries and they seem to be charging fine.The truck is a 2006 F-350 diesel dually CC with a long bed.Any suggestions?

There could be such a heavy load on the alternator with the 5er hooked up to lower the alternator voltage enough to set a code.Did they give you the code or codes?

It would help greatly to have the codes the truck threw. Do you have any type of Scan gauge or other monitor on your truck? Seems strange your truck would lose power from a bad alternator. Did you hear your engine fan clutch come on while climbing the hill. My truck did something similar while pulling our fifth wheel up a hill, it turned out to be a bad fan clutch. Only did it while towing, no load no issue. You need a good engine monitor to tell you what is going on, I have the Scan Gauge II. Tells me the water temp, oil temp, granny temp and FICM voltage. If truck trips a code I can instantly see what is and reset the computer. Hope this helps.

When some rig's electrical system gets below a set value, the rig will go into a lymp mode.

enblethen wrote:When some rig's electrical system gets below a set value, the rig will go into a lymp mode.Yes, that any CEL on your TV warrants a reading of stored codes! The early 6.0's had issues with the Alternator causing the FICM voltage to drop. Did you replace the alternator, how old are the batteries? It may be a good choice to replace all three.

I was plagued with that issue with my 99. It never had any codes when checked by Orilley's inadequate code puller.This was one that had the battery icon that showed up.I finally threw an alternator at it and all was well.:h

Engine light and Wrench code 2006 F-350 Diesel

15 Replies

joelc
Nomad
Dec 22, 2013
I will keep the above in mind. I won't be towing again until next Spring. As noted the problem only occurs when under tow. I will also read up on that "limp mode". Thanks all
Bedlam
Moderator
Dec 16, 2013
I also use the SG II. I monitor for engine and transmission temperatures as well as FICM output voltage and high pressure oil feeding the injectors.
JBarca
Nomad II
Dec 12, 2013
I'll add a plug for the Scan Gage II, if you are towing with the older SD's, get the gage so you have some level of clue what is going on. The stock Ford dash gages are poor other than an extreme event.

Wish I would of added mine earlier. Good luck with your electrical problem.

I have selected engine coolant temp, tranny temp, HP for the fun of it and % slip so I know when the tranny TC is locked. Never been an issue with TC locking etc, just keeping an eye on it.
Dave_H_M
Explorer II
Dec 12, 2013
bucky wrote:
Most OBD code readers are useless on a diesel for other than the most basic codes common to gassers. I'm pretty sure that any charging system issue would light the battery light, not the CEL. Or both if low voltage to the ficm was involved. The variable turbos can cause limp mode on the 6.0s, I suggest a good tech with the proper diag equipment, dealer or independent.

That is for sure. However I think we are beating a dead horse here.
bucky
Explorer II
Dec 12, 2013
Most OBD code readers are useless on a diesel for other than the most basic codes common to gassers. I'm pretty sure that any charging system issue would light the battery light, not the CEL. Or both if low voltage to the ficm was involved. The variable turbos can cause limp mode on the 6.0s, I suggest a good tech with the proper diag equipment, dealer or independent.
enblethen
Nomad
Dec 12, 2013
You can go by an O'Reilly's or Autozone and they will read the code for you.
You can ask them to clear the code, they will not do it unless you ask them.
Halmfamily
Explorer
Dec 12, 2013
joelc wrote:
The batteries are new Interstates. I do not have anything to check the code and unless T40 means something I do not have it. They did try a new timing sensor with no change. Do you suggest I get the code reader or just have the alternator changed as advised. There is a little over 50K miles on the truck.

You can pick up a Scan Gauge II at most local auto part stores and leave it hooked up at all times. Plugs into your OBD II port under your dash. You then can check codes and clear if needed. Should cost around $120.
nevadanick
Explorer
Dec 12, 2013
When you do drive it do go short distances ?
joelc
Nomad
Dec 12, 2013
The batteries are new Interstates. I do not have anything to check the code and unless T40 means something I do not have it. They did try a new timing sensor with no change. Do you suggest I get the code reader or just have the alternator changed as advised. There is a little over 50K miles on the truck.
Bill___Kate
Explorer
Dec 11, 2013
As mentioned above, the 6.0L's often have low voltage problems. The alternators that Ford uses OEM have marginal capacity for the load, especially if you are charging the trailer batteries while underway.

Here is a great website that discusses the whole problem:

FICM Repair

My guess is that your batteries are getting weak, and starting to effect the FICM which is throwing low voltage codes. It is best to take care of it before the alternator and FICM go bad - don't ask me how I know .....