N52 Swap Discussion

[hoveringuy]

Here's my wiring question: Pin 2 of the X6001 is the "Start signal" that comes from the car access module.

The S54 swaps have a similar pin and the explanation is as follows "6. Starting signal [ wire this to pin 18 on X20 it signals dme that engine is cranking]"

This makes absolutely no sense to me as the motor know it's starting from crank sensor signaling rotation.

Is this only related to "convenience start" or is it actually required?

[hubcapboy]

I had it connected to pin 18 on the old version of my wiring spreadsheet that’s linked way back.

It’s also connected here:

https://oomsgfx.com/misc/S54%20Swap/DIY%20Posts%20on%20Forum/S54%20SWAP%20WIRING.pdf

I expect at minimum that this allows a DTC to be stored in the DME for a failure to start. P0512 is “Starter Request Circuit,” so it’s possible this connection is only ever used to log a failure to crank to diagnose a bad starter connection before you buy a new starter motor and pull the intake manifold off.

[nando]

Here's my wiring question: Pin 2 of the X6001 is the "Start signal" that comes from the car access module.

The S54 swaps have a similar pin and the explanation is as follows "6. Starting signal [ wire this to pin 18 on X20 it signals dme that engine is cranking]"

This makes absolutely no sense to me as the motor know it's starting from crank sensor signaling rotation.

Is this only related to "convenience start" or is it actually required?

Wire it to the ignition switch. The engine will not start without this signal.

Actually, if you think about it, the E30 even functions in a similar way. The ignition is not directly activated by the key - the key triggers a circuit in Motronic, which in turn activates the main relay and then physically powers the DME, coil, etc.

[nando]

I had it connected to pin 18 on the old version of my wiring spreadsheet that’s linked way back.

It’s also connected here:

https://oomsgfx.com/misc/S54%20Swap/...P%20WIRING.pdf

I expect at minimum that this allows a DTC to be stored in the DME for a failure to start. P0512 is “Starter Request Circuit,” so it’s possible this connection is only ever used to log a failure to crank to diagnose a bad starter connection before you buy a new starter motor and pull the intake manifold off.

There's a constant battery supply, I don't remember the pin off the top of my head, but the wire label is consistent across every BMW, even as far back as the E30. It's one of the main power pins on the large connector.

But actually, both MSV70 and MSV80 have non-volatile memory - disconnecting the battery does not erase error memory, fault memory, stored codes or anything else. That only really worked on OBD1 cars.

[nando]

I'll have a look at my bench flash harness - but there are 3 power wires that I remember. One constant, one start - and a wake-up signal that is effectively just an ignition switch signal, since we don't need the CAS or EWS modules.

On the E90, wakeup does stuff like prime the fuel pump when you open the door. Not something we need on the E30, but you still need it for things to run properly.

[nando]

I had it connected to pin 18 on the old version of my wiring spreadsheet that’s linked way back.

It’s also connected here:

https://oomsgfx.com/misc/S54%20Swap/DIY%20Posts%20on%20Forum/S54%20SWAP%20WIRING.pdf

I expect at minimum that this allows a DTC to be stored in the DME for a failure to start. P0512 is “Starter Request Circuit,” so it’s possible this connection is only ever used to log a failure to crank to diagnose a bad starter connection before you buy a new starter motor and pull the intake manifold off.

Btw, please try to post errors with BMW hex code values - not generic SAE P-codes. ;)

Two problems with SAE vs BMW:

1) BMW has many error codes that go way beyond the scope of P-codes definitions. At best, you'll get a generic description.
2) In the DME calibration, everything is defined with the BMW hex error code - the same thing you'll see in INPA. Basically, when figuring out a DME function and associated errors, P-codes are completely useless. On the other hand, I can trace BMW hex codes to specific locations and states of memory

You can probably find a translation for SAE to BMW, but my brain isn't that big, lol. It's best to stick to the BMW definition, since many of their codes don't have an SAE equivalent anyway.

[wazzu70]

In the ECU does the P code = hex code?

P3300 = 0x3300 etc.

[hubcapboy]

Oh!

I just mean it was an example of a failure that could only be detected if the DME knew you were trying to crank the engine, but that it wasn’t turning over. I don’t know if it’s even one that this computer checks for.

This isn’t a build thread, but does it make sense to go back and edit and link the current version of a few key documents to the first post? It would make more sense to do that rather than re-post or link to the post every time the question’s asked. I have full pinouts for the 330i from both Bentley and TIS and the Z4 pinout from TIS tabulated with images of the connectors that I could stick there for reference. Do older posts get locked for editing?

[hoveringuy]

I'll have a look at my bench flash harness - but there are 3 power wires that I remember. One constant, one start - and a wake-up signal that is effectively just an ignition switch signal, since we don't need the CAS or EWS modules.
.

That's what my question .boils down to. Does wake up or start trigger the DME relay? If it's wired to pin 18 that means it's only getting power while cranking (and then not getting power).

C101 Pin 5 is IGN which would make more sense if it energizes the relay.

[nando]

In the ECU does the P code = hex code?

P3300 = 0x3300 etc.

unfortunately, no.

[nando]

That's what my question .boils down to. Does wake up or start trigger the DME relay? If it's wired to pin 18 that means it's only getting power while cranking (and then not getting power).

C101 Pin 5 is IGN which would make more sense if it energizes the relay.

heh, clear as mud? I guess ignition can mean two things, cranking or running. I actually think it might work with either temporary power or constant once started. I should experiment on the bench.

[nando]

Oh!

I just mean it was an example of a failure that could only be detected if the DME knew you were trying to crank the engine, but that it wasn’t turning over. I don’t know if it’s even one that this computer checks for.

This isn’t a build thread, but does it make sense to go back and edit and link the current version of a few key documents to the first post? It would make more sense to do that rather than re-post or link to the post every time the question’s asked. I have full pinouts for the 330i from both Bentley and TIS and the Z4 pinout from TIS tabulated with images of the connectors that I could stick there for reference. Do older posts get locked for editing?

I don't think so. I've edited some pretty old posts!

[hubcapboy]

Wire it to the ignition switch. The engine will not start without this signal.

Actually, if you think about it, the E30 even functions in a similar way. The ignition is not directly activated by the key - the key triggers a circuit in Motronic, which in turn activates the main relay and then physically powers the DME, coil, etc.

OK... Circling back to this.... I have notes on this from a month back. There's a connection to CAS on the 330i pinout, but not on the Z4, so I didn't end up adding this to my diagram since we're using the Z4 DME software:

https://www.newtis.info/tisv2/a/en/e...si-roa/ZCDV80b

Pin 2 on the Z4 X60001 is unused, and the DME isn't on the starter circuit:

https://www.newtis.info/tisv2/a/en/e...611491/qCNw2b0

Compare this with the e90 330i where it's listed as "signal, engine start"

https://www.newtis.info/tisv2/a/en/e...i-lim/Fv6vGqhm

And on the component diagram there's certainly a trace from CAS to the DME, but it's *not* tapped from the +12V starter signal, which is pin 22 on the CAS... the DME connects to pin 28 on the CAS.

I had this noted as "probably a problem" because if this is some kind of permission to start from CAS to the DME, the chances of it being just another ignition switched power are pretty slim. If Nando's coded out the need for any CAS interaction, If we don't know what the DME expects on that pin, I wouldn't jump to conclusions and feed it 12v.

[nando]

one thing to keep in mind is there are no hardware differences - it's all software.

The wake-up signal is pin 1 on the X60002 - that needs to go to the ignition switch (terminal 15). I agree that nothing from the CAS needs to be connected, but I don't think it would hurt anything either. I am sorry for causing the confusion, it's been a long time since I looked at the pinout and was going by memory late at night..

[nando]

BTW, This is what the startup subroutine looks like.. yeesh.