Can the PCM be bad?

[skeetdawg03]

Just wondering... when i start the truck sometimes the motors rpms jump from less than 500 to 1000 like its tryin to die then something makes it jump it'll do it real quick and keep doing until i rev the engine up and it'll clear only does when i start it sometimes.. also have some codes on my tranny and sometime the t-converter won't unlock like at a stopsign or redlight.. sometimes it shift crazy up down up down... and goin down the highway keeping a steady speed sometimes the tc lock and unlocks real quick serveral times no hills no load just flat ground no cruise control either it quit... all this started happening at the same time a few months ago.. can't start it with the key I had to bypass it with a starter button... and been noticing my amp meter... when i start the truck its real low... battery's are new and hot optima's red tops... then when the truck runs right the amp meter is past half way which is more than normal.. but if the truck is acting up the amp meter will be low... also my instrument panel lights work when amp meter is up and truck runnin good ... but don't when everything is messing up too.. where do i start is a bad computer is it many wiring problems what do i do??? thanks for any help in advance ... fuses are all good tested with a light probe both sides of each fuse many times...

[89notch]

Check all of the grounds . make sure the connector to the PCM is not loose might take it appart and check the overall condition of the connector itself look for corrosion also.

[skeetdawg03]

checked the connector all the pins looked clean and good... as for grounds what grounds are you referring too... grounds from battery to block are all tight and clean... anyone have any idea what else to check and if it is the pcm how much is a new one...

[89notch]

Originally Posted by skeetdawg03

checked the connector all the pins looked clean and good... as for grounds what grounds are you referring too... grounds from battery to block are all tight and clean... anyone have any idea what else to check and if it is the pcm how much is a new one...

The last PCM I replaced was right at 500.00
As far as your amp gauge being low when first start of the day when the glow plug system is on it draws alot of amperage. Have you done the wiggle test with the truck running ? Might search around on here and find the testing procedure for the glow plug relay.

[sldghamr]

i have heard that the bouncing in RPM's at start is usually the IDM going out or the ICP sensor.

[skeetdawg03]

not the glow plug relay -- been replaced... don't have any problems starting in cold weather without bein plugged in ... whats the idm sensor or the ipc or icp.. sensor and where abouts they located... i've done alot of work on these trucks so i got a pretty good memory where everythings at just don't know the name of everything... i've done buzz test and glow plug test on a computer ... everything checks ok... just something still ain't right and that rpms jumping is very annoying and embarrasing... i'll be sure to check them out soon as i find em ...

[sldghamr]

ICP (injector control pressure) sensor tells the computer what the oil pressure is going to the injectors. it is located right behind the AC compressor, it is an angle going into the driver's side head. there is three wires and colored purple.

[skeetdawg03]

ok i know which one that is... whats the idm sensor you mentioned... if i remeber right the icp sensor was kinda high right i think a buddy changed one out for 120 bucks is that right? or close?

[sldghamr]

Originally Posted by skeetdawg03

ok i know which one that is... whats the idm sensor you mentioned... if i remeber right the icp sensor was kinda high right i think a buddy changed one out for 120 bucks is that right? or close?

the IH version is that much, the Ford version is about $100 more.

[stinky]

I had a PCM that was bad but I didn't know it was bad until I had the dealer try to reflash it. Truck ran perfectly fine.