In the Shed

Hi from Australia!,
Im new here so thanks for allowing me to post.

We have a 2007 Holden( Aussie Chevvy) with LS2 and E38 ECM.

We are working on our father and son project. Turboing this car.
Had it running in the garage and idling away nicely, when it shut off and the dash displayed SAFETY MODE , POWER REDUCED MODE.(I understand this is a LIMP Mode that happens when the ECU has dramas with whats going on etc)

Now it wont start properly now and if it does it idles like a dog.

Plugged in a scan tool and it reported -

SCAN TOOL
P0030 HO2S Heater Control circuit Bank 1 Sensor 1
- may be a random, not important?
P0068 MAP / MAF Throttle Position Correlation
- I take it the relationship between to two, is not as per normal
P0102 Mass or Volume Air Flow Circuit Low
- what it says
P0641 Sensor Reference Votage A Circuit / Open
- some automatic monitoring of the Reference Voltage is not happy

Had a poke around and was going to test the MAP sensor, but noticed when the key is turned to ""ON"" ,that the 5v supply to the MAP sensor ( from the ECM) , is actually only around 4.2v...and it falls away to about 2.2v after a few seconds.????
NOT talking about the reference back to the ECM, talking about the actual 5v supply.

Checked a few other sensors ( Throttle, etc) and the 5v supply to them is exactly 5v, never wavers.

Each sensor is individualy wired from its own pin on the ECM plug. Checked out the plug and it appears fine. MAP is pin X2:43

The Question-

A. Has anyone had this issue ?
B. As the ECM sends out multiple 5v supplies to various sensors in the engine area..seems funny that only 1 of them has died. It appeard from the circuit drawing that this pin X2:43 only supplies this one sensor, and the voltage is no good, with or without the MAP plugged in, i.e. its not a faulty MAP sensor dragging the 5v down.
Would have thought all 5v supplies were all common inside the casing of the ECM? Can 1 only , fail?
Is there a drawing of internals in ECM?

Thanks in advance.
Col

EFIHARNESS

Welcome aboard. There are more than 1 5v supplies in most of ecu's. Unplug all of the sensors that have a 5 v + ref (pedal,t/b,cam, crank. oil press, Etc). See if it comes back. Then start reconnecting sensors one by one until you see the voltage drop. That is your bad sensor. It is rare to have one of the 5v die. Steve

EFIHARNESS

In the E38, 5v1=J1-36,33,34, J2-41,43,44
5v2=J1-56 J2-2,3
All of the signal grounds are tied together. Steve

In the Shed

Thanks so much for your replies Steve.
I am sure that the 5 v to all the other sensors is good i.e. measured at 5v.
Its only the 5v to the MAP that is no good.
I like your ground comment...will investigate.
Thanks
I'll provide some feedback in time.
Col

In the Shed

Ok,,,thanks for the help so far Steve,
Today I confimed the wire out of X2:43 goes to the MAP sensor = Yes.
So I cut the wire off ( grey one) about 3 inches from the X2 plug.
Turned key back on and its still the same...i.e. initially about 4.9v...falls away to about 2.2v after about 5 secs.
Therefore, there is a good chance it is stuffed/broken 5v supply. ( this particular one only).
My only other thought is that this supply has a ""S"" on it on the drawing at the ECM - does that mean is is a ""sensed"" supply, and may shut down if open circuited or overloaded or shorted?...obviously once I cut it , it cant be shorted or overloaded, but may be seen as Open cct and just turn itself off?
If NOT................
Then can I just take the map sensor off another 5v supply....I'm thinking the MAF supply, as the MAFvis no longer there.

So in summary -
1, What deos the "S"" ,mean on the drawing , for some of the 5v outputs at the ECM??
2, Can I just hotwire the MAP to one of the working/good 5v supplies without risking overloding it.

The fact that the 5v suply on X2:43 seems to ramp down, suggests an electronic issue, NOT a bad connection?.
Regardes
Col

EFIHARNESS

You can run all of the 5v+ sensors from one pin. Where is the S on the print. Steve

In the Shed

Thanks Steve,
....& see attached...
Col

In the Shed

...sorry if I sent the pic x 3....didnt see the note about Mod nneeding to approve...appologies.

In the Shed

Today I cut the grey wire from X2:43 and sent the MAP sensor to X2:3 (grey as well, another 5v supply)....5v at MAP sensor now good....so must have been a dodgey one at X2:43.
Thanks again.

Next thing I found was that one of the cooling fan motors ( No2) is open curcuit at the motor itself.
Thus by my reading of the drawing..

Low speed = Fan 1 gets 12v. Fan 2 is off.

Medium speed = fan 1 & 2 in series i e 6v across each motor so the 2 fans both run at 1/2 speed each.

Full Speed = both fans at 12v each so 100% speed/cooling

Thats whats supposed to happen!
But.....because Fan motor #2 is open cct inside the motor ...then this one failure means No Medium and NO High cooling..only Low.
No wonder the bloody thing gets hot.!!

EFIHARNESS

You are correct on how the circuit works. Glad you got it sorted out. Steve

In the Shed

Thanks all your help mate.
Regards
Col