nogomofo1970

SHE DEAD! 2005 GTO ls2
Car wont start after going into limp mode so here's the code P0452 , P0641
and here's the LONG back story.
I recently pulled my intake manifold to move my inlet temp sensor and map sensor . I did some wiring for the meth injection pump, controller and leds.
It idled at 1200rpm after the install so after checking for vacuum leaks and reset the pcm . this worked for few minutes but after i cycled the car on and off the 1200rpm idle returned.
I pulled the manifold off again and checked for leaks , install errors and such . I put it back together and it still idled high....I pulled the battery cables off again and it idled lower( 900rpm) but once again it crept back to 1200rpm and on occasion it didnt wont to fire up .
Besides the high idle the car drove fine so I headed to the track as scheduled . On my second pass it went into limp mode just before the 1/8th mile. I reset the pcm and it fired up and would rev. The high idle continued as well as the hard starts. When I went to make my last pass it immediately went into safe mode as I entered the burnout box and the oil warning light came on.
I parked it , checked the oil ( PERFECT LEVEL and pressure) . I disconnected the ,hooked it back up and attempted to fire the car but this time it didnt even try to start. Eventually I gave up and towed it home .
It seems to act like a faulty cam position sensor but the codes point towards a wiring issue so I pulled all of the meth wiring out , rewired my extended map sensor wires.
One weird thing is the aeroforce gauge oil pressure read 65674 so i'm thinking something may be up with its cable.
Would a pinched oil pressure sender wire not let the car start?
I no its a tough read but I figured the more details the better!

2xLS1

iTrader: (25)

P0641 pretty much spells out the problem. The 5V reference voltage in the PCM is bad. It goes to the following sensors.
The manifold absolute pressure (MAP) sensor
The engine oil pressure (EOP) sensor
The fuel tank pressure (FTP) sensor
The air conditioning (A/C) refrigerant pressure sensor
The accelerator pedal position (APP) sensor 2

The P0452 is for the fuel tank pressure sensor. I bet you shorted the 5V reference to something screwing with the MAP sensor wiring.

nogomofo1970

So if I get a new pcm can I just bolt it in place and flash my tune to it or is there a bunch of dealer **** that needs to be done for security?

2xLS1

iTrader: (25)

Why don't you look for the short on the 5V bus like I said?

67Lark

I had an 02 sensor wire hit the header one time, melt the coating and then short out and blow the 5v reference fuse. Only code I had was for MAF though so it took me a few minutes to find that issue.

2xLS1

iTrader: (25)

O2 sensors and MAF are fused on a 12V circuit. The 5V reference is generated in the PCM and should be buffered to where a short can pull the voltage down, but removing the short allow the 5V to be restored. OP said he moved the MAP sensor. If that involved the MAP wiring there could be a wiring error as the MAP uses the 5V reference.

67Lark

Well I could have sworn it was a 5 volt but it was also 8 years ago so my mind would be faded, that car gave me all kinds of fits.

On a side note there is a reason I am here because there are many people smarter than I who can explain things better. Thank you

nogomofo1970

I read into your comment wrong. I thought me shorting the 5v signal bricked the ecm . Thanks I'll continue hunting for shorts. I've already gone through the map circuit so I'm going to pull the oil pressure one and check it out.

ViaBellator

iTrader: (2)

Did you ever get this worked out? Getting that P0641 on my 04 GTO and cant find anything shorted.

I disconnected the MAP, A/C, TPS, Oil Pressure, MAF, and any other sensor I could find and still only get 2.68v on the MAP and TPS. The others all read 4.98v