Issue: Driving at 70 mph, 2004 ford f150 lariat -5.4 L triton pickup, with 204 K miles, suddenly the AC stopped blowing cold air, heard a small noise , shut down the AC, and the engine safe mode came on dashboard, went down to 30 mph and went to a friend auto shop, put a professional mechanic scanner with Ford modules software and the scanner tool read 11 codes. From camshaft sensor, to O2 sensor, to crankcase sensors- both banks, to evaporator, to coil ignition no1 spark plug, to a retarded timing issue, really UPSET ME to see that many codes. Returned to the house and truck was misfiring and MPG level went down to 4 mpg. opened up youtube and started to see potential codes and cost to repair. My mechanic said to start with Spark plugs and work from there. Still had the AC issue- I'm in South Texas 101 F, not pleasant at all. So review the fuses for the AC, and check fuse no 11, ok, fuse 12- 14, Ok, go outside - check relays, take out and put back, and then checked fuse no 32, AC clutch fuse, and it was blown. Replaced the 15 amp fuse, and started and run the truck in highway, got to 80 mph, smooth as before, no issues at all. No engine safe mode, my mpg went back to normal, and NO MORE misfiring and engine trembling. !!!! how in the hell does a 15 amp fuse cause so much trouble to the computer !!! Pretty sure there are going to be some Alien conclusions .

 

Here comes one !
We don't know at this time why the clutch consumed so much current it caused the fuse to blow.. A 15 amp fuse is a little low for a magnetic clutch to power it.
This could be only the beginning..
What ever caused that clutch or what the fuse powers, to pull the voltage available to the rest of the computer controlled parts down , rendered them non functional , hence all the codes. This is not unusual because computer controlled parts and the computer are extremely voltage sensitive.
What really should be considered is to find the reason for the short circuit.
This can and very possibly will happen again, so expect it until the problem is found and corrected..

You might save yourself some time and $$ by having a good electrical shop handle this problem.

Did ANYBODY do ANY kind of work on the AC system ?

 

I haven't pulled the AC compressor yet, waiting for a new compressor, condenser, and air dryer kit. Will replace all and see what happens. The system is old,and do need to replace. will find out what the engine does after replacement.
1. Does the PCM go bad after an incident of high voltage?
2. never seen so many codes for a high voltage issue - especially coming from the AC compressor.

Will re-post when all is changed in AC system.

 

Tony,
What will you do if after spending all that money, time and labor and still have the same problem ?

I believe you are blaming the AC system when you might want to consider looking into an electrical problem that shows up when the AC system is working.

If there is a wire that may be contacting an unintended ground at certain times , that could cause a fuse to blow.
That certain time could be when the AC system is requested to operate.
I guess it s OK if you have the time and $$ to spend possibly replacing a lot of good parts.

Do you have the equip to evacuate and charge the system when you are finished replacing these parts ?

 

Just fix the AC first and ignore all other codes, they should go away.
Your truck has multiple control modules, and they need to communicate thru a BUS system. When one device within the BUS system goes down, it can bring down multiple devices on the same BUS. Not sure if that applies to 2004 F-150 though.
Let me give an example on a BMW 3-series there is a BUS called BSD and it consists of water pump, voltage regulator, oil level sensor and IBS (intelligent battery sensor) located on the battery ground terminal. When either one of the 4 devices is down, the other 3 will be brought down as well. When it's brought down there is failsafe profile so the vehicle can continue running. Some other non-BSD devices can still be brought down when it's in failsafe mode, for instance, ABS, SRS, power window and HVAC. That said, just replace what you have to replace on the AC and troubleshoot one at a time.

 

Heiko,
Could you please provide a schematic diagram of his 2004 ford vehicle so we could see where the power to the system originates ?
We would need that info to determine where the short in the system might be located?

For kicks , also show the BMW diagram so we could see just how different they are one from the other ?

The diagrams will clear all that up, thanks.

 

Find attached Powertrain_Control_Software.pdf
Google "ford multiplexing vs bus" to find out more.
Briefly, "multiplexing" (used by Ford) is just a BUS system that allows multiple devices to share the same communication line.
The advantage is to avoid running 100 wires to 100 devices. The disadvantage is, as mentioned in my previous message on a BMW's BSD line, when a single device (out of 4) is down, the other 3 devices that share the same communication line will be down as well like this:


You'd get the code but are they really missing, absolutely not. In my previous message I mentioned "there is failsafe profile so the vehicle can continue running", let me provide a bit more examples. The voltage regulator (at failsafe mode) will be set to constant 13.7V. Since most BMWs don't have a dipstick to check motor oil, and when the oil level sensor is brought down, you just can't check the oil level. BMW decide to set the water pump to run at full blast (until it's fully in sleep mode) even when engine is off key is out when illuminated / keyless entry system is triggered (i.e. you pop the trunk with FOB), and this can drain and kill the battery in no time. Running full blast is still better than not running and overheating the engine. Anyway don't want to get off topic further. Just wanted to let Tony know that he shouldn't worry too much. In worst-case scenario replace or repair the PCM, like the BMW's BSD example if all 4 devices are found to be in good working condition.
Tony stated that no.32 fuse was blown and he's waiting for the new parts on his AC system so let see what he says when he's done on that.


Pinpoint i attached below. I also captured a section from pinpoint i in picture below you can see it's on UBP bus. So hopefully it's his A/C that brought down or set to fail-safe mode to the other devices on the UBP bus.

 

Thank you for the info.

What we do know, Ford used the "Std Corporate Protocol" system for communication previous to 2008 after which they utilized the CAN bus system .

There is no comparison between a Ford and a BMW which can be a whole different animal.

The CAN system , Controller Area Network, does use various modules to compose the system network, but "Modules " were not used prior to that time. There is an exception to the module description , which called the fuel gauge sending unit , the pump module.
What I believe we are missing here is a simple intermittent electrical problem and will be incurring a lot of unnecessary expense throwing parts at what we "think" is the problem and not what really should be proven before replacing anything.
The AC system ,so far, as we know is functioning as it is supposed to function , cooling when requested. When we start replacing a lot of parts that have not been verified faulty, the can of worms is opened.
There is a lot more to AC work than replacing parts we suspect to be malfunctioning and that is why we go to a "good " shop to obtain an accurate diagnosis.

A perfect example is , start with replacing the spark plugs as was suggested to correct the cause of all the codes coming up
If a potential customer has no idea of what is happening, I guess he is fair game.

 

Hey Hanky, you were right, the issue was the engine cable harness, there were 4 wires with scraped middles, and copper wires had been exposed. retaped each, and the truck and AC system work fine. Took time to open up the harnesses and go through it and find the issues. Bottom line - potential repairs amounts of thousands - thinking ECM replacement, plugs, coil packs, camshaft sensors, O2 sensor, MAF sensor, VVT sensors, all came down to 4 wires.

 

Thank you for the update.
Glad you found and repaired the cause.

As far as being right,
When we were right, nobody remembers , and when we were wrong, nobody forgets, lol.