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MTX65

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2012 Ford Expedition 98,000 miles. 5.4L

Wife was driving home the other day when the instrument cluster went haywire. Check engine light, service advancetrac. (Abs and traction control light) no reading for oil life, no reading for mileage, antitheft light flashing. Rpm’s and Spedo went dead. Car died off on her. Towed home and sat for 4 days (I was out of town thinking maybe alternator battery)

Get home and car cranks over. Runs for about 5 minutes and all the same problems happen again, car shuts off and never starts back up. Car in the on position battery voltage is good (can’t load test it) windows, AC, lights, and seats all operational. Vehicle makes not signs of an attempt to crank. No clicks from in the cab or engine compartment either. Read codes. There were a bunch of them that I should’ve written down. I cleared them to see what was active Only consistent was U1055.
I receive a "device unable to communicate with the control unit" for the following

PCM
Abs
RCM
IC
APIM
Dsp
Gpsm
RCU
RETM
TCCM
SDARS
And VDM

Checked fuses and obvious ground wires as well as snug connections to the fuse box and battery.
Spoke to a mechanic on a website that concluded he believed it was the instrument cluster. Shipped off for repairs. Just got a call from them advising their in house testing is showing the unit operational.

ABS module repaired last year. All original keys. No new repairs or noted problems prior to this happening.
 

Trainmaster

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Try jumping the battery with a known good one. The failure describe sounds like low voltage. Is the belt still there? Either the battery is bad due to a failed alternator or bad cell or you have a loose wire.

The starting circuit on these trucks is very basic. If it's not cranking, there's not much that can be wrong: Low voltage, deteriorated wiring or a failed ignition switch. There's a relay and neutral interlock too, but they wouldn't affect the truck's running.
 
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MTX65

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When the truck shut off, my wife jumped it to get it started. Started right up until they removed the cables. Immediately died when cables removed. (That’s why initial thought was alternator) few days after initial problem it cranked over no problem for a few minutes before dying off. Battery test was good voltage wise. I don’t have a load tester but I figured after a few days battery voltage being good and cranking over temporarily, alternator would be eliminated no? (Correct me if I’m wrong) I’m starting to lean PCM due to circumstances. I’m just trying to avoid dealership prices if there’s anything else I can self diagnose/fix.
 

BigOleFordFan

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I had some similar issues with my 11 EL Limited.... it died on me one day and was throwing a bunch of no-comm codes too, along with the PATS flashing padlock and not starting, so after 3 months & $3K worth of diagnostics and replacing the ignition switch, both keys, several wiring harnesses, the HALO sensor, and some other stuff, the 3rd ford dealer I took it to finally solved it....it was the "run/start relay" that was fried....

Thankfully, all is well now :)
 

99WhiteC5Coupe

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Your problem sure sounds like a bad battery with a defective cell and/or loose or corroded terminals and/or cable connectors.
 

Yupster Dog

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Second what @99WhiteC5Coupe said.


You can not diagnose anything electrical until you know it has and is getting the correct voltage.
Start with your battery Go get it tested properly, any Auto parts stores do it for free.

Once you know that you have a good battery
do a Voltage Drop Test to make sure all your connections and cables are good.

Only then can you start to diagnose. Unless you like running in circles
 

Snuffy

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Check for a loose positive battery cable around the post due to corrosion. It’s a known Ford problem that does NOT require replacing the entire wire assy.

Basically the positive cable no longer has full contact w the battery post and nothing works. It if happens while driving, or if it’s loose and making intermittent contact as you drive it might do the same thing as you’re experiencing. It’s a fairly easy DIY repair.

(https://static.nhtsa.gov/odi/tsbs/2019/MC-10164497-0001.pdf)
 
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MTX65

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I had some similar issues with my 11 EL Limited.... it died on me one day and was throwing a bunch of no-comm codes too, along with the PATS flashing padlock and not starting, so after 3 months & $3K worth of diagnostics and replacing the ignition switch, both keys, several wiring harnesses, the HALO sensor, and some other stuff, the 3rd ford dealer I took it to finally solved it....it was the "run/start relay" that was fried....

Thankfully, all is well now :)
I checked the run/start relay via multimeter. Shows it’s operating normal. I’m seriously at a loss.
 
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