2004 Ford Truck Specs:

Ford 5.4L V8 engine and has 215,000 miles on it. It uses a SFI fuel injection system.

Symptoms:

This 2004 Ford truck with code P0503 hesitates and cuts out at around 55-60 mph at around 3000 rpm in 3rd gear. VSS reading in the scanner is fluctuating at idle speed and goes up to 120 mph at highway speed although speedometer reading is OK. Had P0503 intermittent VSS Code.

DIAGNOSTICS for 2004 Ford truck code P0503:

As per our scanner, the PCM is seeing vehicle speed thru VSS sensor signal coming from ABS controller. With VSS sensor disconnected, the hesitation/idle fluctuation remained. With all aftermarket lights and radios recently added and disconnected, still the same results. Did alternator diode test and was found bad. Replaced diode but the same results. Finally, with ABS controller removed, all hesitation/fluctuations were gone. (Note: Checking the latest TSB and updates did not help).

Sent the truck to the dealer and they replaced the following: ABS controller including 2 ignition coil plugs, mass air flow sensor. And the problem is the same when returned to the garage.

Solution:

Checking with the Ford dealer, they admitted installing a good “known” coil plugs. Checking it further with other Ford dealer garages, we found the coil plugs were notorious for hairline cracking not visible to the naked eye. Replaced coil plugs with new OEM parts and problem was solved.

NOTE:

The approach used in solving this problem is only one of the strategies offered by ATS using the common database which can be improved to get maximum savings effect. This 2004 Ford truck code P0503 can be easily fixed if you have the right information as shown above. However, having an online mechanic to assist you will be really beneficial so you can do it safely.

Thanks!

Richard