Ford Dave 2004

How do you tell if the pcm is bad and what are the symptoms?

F150Torqued

It would take a 'supercomputer' a whole freaking year to answer that question.

DarrinT04

click this:
https://repairpal.com/pcm-power_train-control-module

F150Torqued

Well - there's your answer.





its a start, but depending on the endlessly wide range of symptoms a defective PCM could produce, I don't thank we're really any closer to an answer.

RL1990

First there are many modules (computers) on the truck and they all talk to each other over the truck's network. Connecting a code reader (an advanced one not a cheap one) to the computer would show communication fault codes. These are codes that will start with a "U". If the PCM or network is completely shot the scan tool will say it cannot communicate with the network.

techrep

iTrader: (1)

650NutKase

You would need a good scan tool, not a little plug n read. Look on youtube from South Main Auto. Eric does a good job on describing when a PCM is bad. Usually, a communications fault code will come up and the scan tool will not be able to communicate with the PCM. Of course, that is only ONE scenario.

Ford Dave 2004

The problem I am having is that I can not find any answers as to why my truck stalls at stop signs and lights. Never has codes and shops have checked for bad wiring and plugs. They are now telling me it must be bad computer. I can find nothing to solve this issue. I need to get this problem solved and then I will do timing and oil pump. But will not spend money on going further if I cant get the stalling corrected.

F150Torqued

"stalls at stop signs and lights" is a broad general description. (Will it NOT stall at a Rail Road Crossing or a School Bus Stop?). JK!

Then you say you'll do a timing job / oil pump once this is solved. Hell, the stalling may be BECAUSE YOU NEED A TIMING JOB. Especially on an '04' - depending on miles (another parameter not given) and more specific symptoms.

Is it a rough idle to the point it dies, or does it just 'die' - 'go dead'? Will it start right back up - or make you have to goof with something to make it run again.

If it just DIES - dead, like ignition was shut off, then will start up again without a'doo, it could be all kinds of electrical other than the PCM. For example - the 'crankshaft position sensor' is one component that can do exactly that.

Doublet74

It could also be as simple as your throttle body needs to be cleaned.