Thanks for the replies guys...
Please don't take this as expert diagnostics (fires and otherwise taken at own risk ), i would grab a pair of trusty side cutters and snip the wire from ECU to MAP 5v rail and supply the MAP rail with an external source 5v to see what happens (connected to the MAP side) leaving the ECU end "open" , usually? a 5v rail is low current supply to various sensors but who knows what they have on the bottom end of some of the outputs ?
May yet try that mate...however, I think if the ECM still ""believes"" there is a Ref Voltage isse ( P0641) it may still not behave, even though the MAP is now happy.
Had a very similar problem on my Harley not long ago.
A bit of a background.
There is a 5v supply that supplies a number of sensors.
The computer will monitor continuosly at least 1 of these.
In the case of the Harley it was the MAP sensor.
The computer needs to see a minimum voltage returning from the sensor otherwise it will get unhappy.
I replaced the MAP sensor but that didnt cure the problem.
There was another sensor supplied by the 5v that was the problem.
Turned out to be the speed sensor in the case of the Harley.
Suggestions.
Grab a wiring diagram and find all sensors that run off the 5v supply.
Get your multimeter on to one of the connections and leave it there for the time being.
Disconnect the other sensors one by one and check the voltage.
Once you have disconnected the offending sensor the voltage will come back up to 5v
Yeah, I have checked the other sensors that are available, and they all have a nice 5v, thus Im assuming the ECM has multiple supplies.coming out, almost sensor specific? The schematic shows only 1 device connected to ECM plug X2:terminal 43 = MAP sensor. However my issue is the same with or without the sensor pluged in at the sensor end. . I do plan to unplug the big X2 plug at the ECM and see if pin 43 has a nice 5v on it with the big plug/harness removed, but Im thinking that plug also supplies the 12v to the ECM, so it will now be dead. Regardless I'll do it and see, as if there is 5v on the other 5v output pins, but not on 43 , with the big plug out, then its gotta be a dud ECM. i.e.the internal supply to pin 43 is rooted.
Hi Col, i would have thought that the ecu would recognize that the maf was no longer in use in the system. As your tuner would only be using the map now, i know that the map is on the back of the manifold on the ls1 & ls6 manifold & i thought it was at the front of the ls2. Assuming that you have checked the wire condition & map to see no damage is visible? Have you tried fitting a new map sensor in ? I think you where asking a question about maf map & throttle sensors, not trying to be rude, but originally it had a maf (mass air flow sensor) in the intake before the throttle body, on the throttle body which is a drive by wire, there is the tps (throttle position sensor) & iac (idle air control sensor) & then the map sensor is what will be running the settings now, seems that the maf is deleted i have another ecu but not here. I could have a look to see if i have a ls2 ecu layout drawing. Ls1tech.com is a great website for information on all things ls as well. Theoretically your tuner should most probably be the 1 to look at this issue for you, I'd run it there on the trailer. To me a sensor or relay is usually the most common fault of anything, especially when. the computer system is inside the vehicle in a ve. the early vx type had 1 of the 3 in the engine bay right underneath the header tank ? So I'd try a new gm map sensor and check the wires 1st, heater sensor bank 1 sounds to me like the water temperature sensor in the passenger cylinder head at the front i see it says sensor 1 so obviously it is the 1st sensor in the system to give a reading & it would be pretty close to the exhaust manifold & the back of the turbo might pay to fit a new 1 of those & some reflecta sleeve around mate ! Gary.
Yeah Gary..you have touched on a few things there....I wasnt smart enough to remember that the MAF was now non existant.! doh. Thus the DTC codes related to that are probably b.s.
Hae not tried a new MAP sensor, as the issue is the SUPPLY to it, rather than the device IMHO. Am looking for a ECU internal drawing, havent found one yet.
You are right mate, best to hand it to the tuner....he may well say "" yeah, the ECM ramps back the 5v to the MAP when its in safety mode!!"" or whatever..just to me , a 5v supply should always be 5v, and any signal manipulation should be done to the feedback signal.
Have unplugged the sensors near the turbo pipes, and no difference.
Will ring the tunetomorrow and see what he reckons.
Appreciate the help guys.
Ta
Col
