Powertrain Diagnostics Enable wire coming out of E38 ECM
Powertrain Diagnostics Enable wire coming out of E38 ECM I'm working with an LS2 out of a 2005 SSR going into a custom rock buggy. Chopping the harness down I see there is a wire that is labeled "Powertrain Diagnostic Enable." Its the only wire in the entire harness whose function I don't completely understand. Does it run to ground or 12-volts, switched, unswitched? The name could mean two things. One interpretation is that it the ECM checks to make sure all sensors report non-fault and then powers that wire to enable the vehicle to start. The other is that you apply power to enable some sort of diagnostics mode. Anyone know?
J. J.
J. J.
Whats the pin location wire color? Where does it say 'Powertrain Diagnostics Enable', is that a fuse?
Also, isnt that a 24x engine, shouldnt be an E38 if it is an 05. I could be wrong.
Jon
Also, isnt that a 24x engine, shouldnt be an E38 if it is an 05. I could be wrong.
Jon
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Thanks for the reply.
First, want to appologize, the subject contains a typo. I blieve that I have an E40 ECM, NOT an E38.
It is a white w/black stripe wire in the blue C1 connector position 10 labeled "Powertrain Diagnostic Enable."
I've looked it up in the Alldata wiring schematics for my donor vehicle and can trace it as far as the main power relay. It is the signal wire for the relay which powers all of the injectors, coils, etc. I don't recall at this time if it is + or - though. I will post the diagram tomorrow. I will not be using a main powertrain relay as the stock setup had so I need to figure out what to do with this wire. Ground it, apply power, whatever.
Here's a pic of my ECM:
(Not mine specifically, mine does look exactly liek this though.)
Obviously, the rig isn't running yet. I did temporarily wire up a bench harness to pull my tune out of the ECM with HPTuners so that I could start looking at it and get aquainted. To get it to read the ECM I had to apply power to the wire in quesiton. I don't know for sure that that was the correct thing to do though as there was another wire I was experimenting with at the same time that needed to go to ground. I experimented with both at once and it worked so I don't know if it was applying power to the wire in question that did it, grounding the other wire, or both. I do know for a fact now though that the one I grounded has to be grounded for it to work which leaves this one wire open to question.
Thanks for the help.
J. J.
First, want to appologize, the subject contains a typo. I blieve that I have an E40 ECM, NOT an E38.
It is a white w/black stripe wire in the blue C1 connector position 10 labeled "Powertrain Diagnostic Enable."
I've looked it up in the Alldata wiring schematics for my donor vehicle and can trace it as far as the main power relay. It is the signal wire for the relay which powers all of the injectors, coils, etc. I don't recall at this time if it is + or - though. I will post the diagram tomorrow. I will not be using a main powertrain relay as the stock setup had so I need to figure out what to do with this wire. Ground it, apply power, whatever.
Here's a pic of my ECM:
(Not mine specifically, mine does look exactly liek this though.)
Obviously, the rig isn't running yet. I did temporarily wire up a bench harness to pull my tune out of the ECM with HPTuners so that I could start looking at it and get aquainted. To get it to read the ECM I had to apply power to the wire in quesiton. I don't know for sure that that was the correct thing to do though as there was another wire I was experimenting with at the same time that needed to go to ground. I experimented with both at once and it worked so I don't know if it was applying power to the wire in question that did it, grounding the other wire, or both. I do know for a fact now though that the one I grounded has to be grounded for it to work which leaves this one wire open to question.
Thanks for the help.
J. J.
Last edited by patooyee; Jul 28, 2010 at 11:50 PM.
Here's the schematic. Turns out I had it handy:
Looks like its a + wire. My theory is that I just need to run it to 12 + volts or into my ignition switch. I'm new to this though so I guess I'm just looking for verification.
J. J.
Looks like its a + wire. My theory is that I just need to run it to 12 + volts or into my ignition switch. I'm new to this though so I guess I'm just looking for verification.
J. J.
Yes. It appears the PCM is providing ground to that circuit to switch the relay on, so you must provide power with key on/crank only. Looks like you answered your own question : )
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Verdad Gallardo Thinking about it more ... is it possible that I don't even need that wire? This diagram shows that it signals the powertrain power relay to turn on. I won't be using a powertrain relay though. My intent is to just power all the items powered by that relay in the above diagram via ignition switch power.
This gets me back to my main question which is, how does the ECM determine when to ground that wire? Does it have some sort of internal diag check that it goes through and if passed, grounds that wire?
J. J.
This gets me back to my main question which is, how does the ECM determine when to ground that wire? Does it have some sort of internal diag check that it goes through and if passed, grounds that wire?
J. J.
It may have something to do with the antitheft. For instance, when the transponder in the key is verified by the BCM, it sends a signal to the PCM which in turn grounds that circuit, enabling the relay. In your case, you are probably right. You could just bypass that wire, and hook a standard 'key on' relay to those circuits to power them. Just a thought. Havent messed with those PCMs much as I went right to the E38s. Hope this helps.
Jon
Jon
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