Ryan00TJ

iTrader: (8)

Yup, Whipple....

https://whipplesuperchargers.com/ind...&product_id=73

soonenough

So would the Iac driver cause the power to cycle to entire system like in the video?

Also is their any specific procedure when swapping PCM's? I don't want to screw up 2 of them.

sutphen 30

ohm out the iac wiring back to the pcm,,make sure its not shorted to ground anywhere.

sutphen 30

wow,,It only took me 30mins to fix my friends pcm on his 1075's.gonna have to bill him some extra mula.

soonenough

How did you repair it??

Keith Atlanta

So, if you fry the ECM it does what he has in the video?

OP - Did you figure it out?

soonenough

I worked on it today and no I haven't figured it out. It was happening at random today.

Here's what I know.

The Iac is new and the wires are not grounding out anywhere.

Swapped relays one at a time. Relays are good.

I tried to get a reading on ignition switch but couldn't get to it while it was acting up.

I did have a MAP input hi code in the history I'm not sure if this has to do with it

Here is another video from today. Notice the erratic alarm and relays. It does this with just the key on.

https://youtu.be/l322_TPba8c

sutphen 30

opened the pcm up,,saw the fried transistor and replaced it w/ one from a spare pcm I had laying around.put it back together and its been fine ever since.

BUP

iTrader: (9)

sounds like you have a VOLTAGE Problem to me --- you can even hear the fuel pump(s) turn on and off on their own. Loose battery cable at the starter is my guess or back side grounds for the easy fast checking areas .

Info --- The IAC that fails can knock out ECM 555 / PCM 555 no matter of the engine - 4.3 / 5.0 / 5.7 / 6.2 = ECM 555 --- then / 8.1 PCM 555. An IAC that fails can knock out IAC driver internally in the ECM / PCM - this can lead to many problems for the engine including not even starting. IMPORTANT Have you checked the fuse for the IAC circuit ??? is it good and connected properly ? Do you have power there ??? I would check there ASAP.

Open your throttle half way does the engine start ??? Open your throttle fully --- but be ready to pull back very quick if the engine starts.

What is fuel pressure here - even while cranking ? Put a fuel pressure gauge on this engine and monitor the fuel pressure while its cranking and trying to run

IMPORTANT watch your volt gauge or use a volt meter or the scan tool to watch your engine voltage. Key on what is it ? steady 12.7 volts ??? or is voltage dropping / or coming and going, if so the fuel pumps will never keep fuel flowing period because they require steady correct voltage to operate, just as every thing else that requires correct steady and stable voltage. Important areas to check, So voltage is number one area to check first.

You have to rule out what it is not the problems and problem areas - so testing is what you need to do first before the parts changing takes effect here. That's a waste of money for any boater and a dart thrower way to fix a boat. .

Your location is ??? In person this would not be hard to diagnose at all.. Just to start with the testing is 1, simple stuff first - do you correct voltage and all the time steady correct voltage even for cranking the engine ? - next is do you have fuel moving when the fuel pumps come on and while cranking - does it maintain correct fuel pressure of no ? Next is do you have CONSTANT steady spark even while cranking - sealed inline spark checkers best cheap tool to have. These are always the easy first checks to perform when an engine does not start -

You can watch voltage drop or rise using the scan tool - or even with a cheap volt meter. Check the starter for any power problems ie : battery cables, 90 amp fuse at the starter - then back side grounds - then the 50 AMP fuse engine side if applicable since you did not post an engine serial number here - Next the main power relay do you have power there ??? and so on. You need correct steady power all the time at every 12 V system on the engine INCLUDING back side of the ALTERNATOR --- did you check connections there as well and voltage ????.

NEXT IMPORTANT do you really know how to read the scan tool - not having fault codes means nothing - you said you had a map sensor fault ? You also could be having a problem with the 5 volt sensors harnesses especially on the back side of the engine. There is also a smart transom circuit / harness as well that is a 5 V. .

Instead of 100 % automatically thinking the IAC driver in the PCM is bad, why not test the IAC ??? Back to scan tool, what is the IAC reading with key on and when the engine starts ? This can tell you what is going on before jumping to huge conclusions. Like I said you have to test all these things and rule out whats not the problems and problem areas, moving forward to be able finding the problem area(s).

It also looked as you had a tach signal at the gauge in the video, IS THIS CORRECT ??? If not at all then Crank sensor si bad ? But 99 % of the time a truly bad crank sensor the engine will not start at all and you will not have a tach signal.

I gave out a lot of good info here and if you are close to Texas - I have to say this would not be hard for me to figure out all the problems in person using the proper tools and the proper way to test systems that would pin point the engine issues and a no start running engine. .

BUP

iTrader: (9)

What ECM MEFI 1 ?

You just do not open up ECM's like with what with a jack knife ?? If he did fix a PCM 555 controller he got darn lucky as hell period.

Also I have been getting into more and more of the ECM and PCM testing if there is a problem with them plus have fixed some as well. With that said - not all ECM's are fixable either. I would have to say about 50 % of what I have seen is and 50 % not fixable.