scottboy69358

have faults for intake air temp high and low and manifold pressure high and low. ive replace both the map sensor and the iat sensor after i pulled the harness and tested every wire with 5 ohms or less. any suggestions i replaced the ecm about 1 year ago for other issues and dread the thought of doin it again

Busboy

Have a look down around the AC compressor for a sense wire rubbed through and shorting to ground.

scottboy69358

thanks for the suggestion

i pulled the harness out and removed the split wrap to make sure i wouldnt miss anything and still cant find anything wrong with the wiring
its startin to get a little frustrating ive been fightin this thing for about two months
any help is much apprecitated

rickf

Have you removed and cleaned all of the grounds for the harness? I mean all of them, the computer ground especially. I can't tell you where they all are on your truck but what you are describing sounds like a PCM ground issue.

Rick

scottboy69358

thanks for the help
i pulled the grounds cleaned them with a buffer. there are two or three on the block and a few on the cab. i cleaned the battery cable ends for both batteries. it seems to get alot worse when it get up to operating temp i took it out to do chores yesterday and the first 6 miles or so it ran ok but as soon as it got warm it went to no boost fuel and didnt fix itself for the next two hours

rickf

IU see where I wrote PCM and it probably should have been ECM since it is the engine control section. If you cleaned the other grounds I am sure you have already done these also. Sorry for the mix up, not getting much sleep lately. ECM's are usually pretty reliable but a lot of things can take them out. the main enemy of any computer, auto or home, is a voltage spike. Have you had to jump start your truck or someone else lately? It is definitely heat related and with the computer mounted on the engine I would have to say it is a strong possibility. You have checked most of the things I would suggest.

Rick

Do you have a scanner that will allow you to see the data from the sensors? That might give you some hints about if the data is bad or the processing is bad.

Busboy

You say you had the harness off and looked at the wires, do you mean the complete engine harness or just the part going to the map and iat? The ECM reads oil pressure, engine coolant temp, water in fuel, apps along with IAT and map. I forget what the wire was for that rubs through but if you search on here you'll find it. It's down by the AC compressor but I don't think it's for the AC as the hi and lo press sense go to the PCM. It sure sounds like an intermittent short causing a power fluctuation.

scottboy69358

i dont have a scanner to read the active data but it will take snap shots. the grounds are all in decent shape all my conections are tight. i hate the thought of replacin the ecm again but my truck lives a hard life im sure the vibration of dirt roads every day and the constant hot and cold wet and dry are prolly the leading factors that have killed it

yess i pulled the harness all the way out was not fun but it was alot easier than tryin to look it over in the truck

thanks for the advice yall this truck is gettin tired i think.

rickf

Before buying another ECM I would find someone with a scanner to verify the data stream. Like I said, ECM's are pretty dependable and to have more than one go out raises a red flag. I would also check the voltage from the alternator with a DSO to make sure you are not getting spikes from that alternator. That could tske out the ECM.

Rick

scottboy69358

thanks for the input it will take a few weeks but ill get her into a shop and let ya know what they c with a scanner and alternator

chg

So what was the outcome? I am having the same issues.

scottboy69358

traded the truck and got an 08 after tryin to figure it out for a year and lack there of shops in my area with the capabilities and or knowledge to work on it i threw in the towel

scottboy69358

what did u find with urs chg