I have a 96 Ford F350 5.8 e4od automatic transmission on random occasions the overdrive off light will start flashing and trouble code 452 will be in the computer I have checked wiring from the programmable speedometer odometer module to the PCM have found no problems in the wiring how can I tell if the PCM is bad and causing this problem because when it acts up and throws the code the speedometer has no signs of defect the truck has 349000 original miles so how would I be able to tell if the PCM is bad and causing the problem