The 5-minute MFTS mod

[S2central.net]

Takes a lot longer to describe this than to do it. Applicable to all S2 engine variants, but not the AAN engined S4/S6.

For background there are two high temp alarm signals at the MFTS - one (the C pin) alerts the driver via autocheck (same alarm as if coolant level is low). The other (R pin) tells the ECU to turn boost control off and you fallback to mechanical boost control (0.4bar with stock spring).

If both alerts work at the same time then all is well, but if one of those alarms fails to trigger then the ECU and driver (via Autocheck) aren't in sync.

I have a very simple wiring mod that logically ORs these alarm inputs, such that if either the R or C pin goes to ground (they are thermal switches - its what they do) then *both* the ECU and Autocheck will be informed simultaneously.

Its really easy - all I used is a short section of single-core mains cable - maybe 2-3cm or so which I trimmed down keeping the insulation on except at the ends to expose the bare wire.

1 - Remove the top portion of connector T8f and tease back the connector hood

2 - Gently insert the jumper link between pins 3 and 5 - they are numbered - but its the blue/white wire and blue/yellow wire

3 - Carefully apply some insulating tape around the modified T8f connector so that the jumper link cannot fall out and refit the hood.

4 - Use a multimeter to test on the connector face at pins 3 and 5 that the link is OK

5 - Refit the T8f connector

I was able to use an ECU breakout box to force the R-pin into the alarm state by pulling it to 0V - this raised the AUtocheck alarm after 2 secs - and I was only able to hit 0.4bar on a roadtest. On removal of the alarm condition (at breakout box) it took about 10-12 seconds for the alarm to clear from Autocheck and I had full boost restored by my ECU.

Brilliant and easy IMO. Photo of modded T8f connector (before tape application) attached hopefully.

Paul

[S2central.net]

I used the VAG1598 breakout box to force the R pin alarm active...

[S2central.net]

And this appears on the Autocheck display...

So now I get WGFV shutdown *and* Autocheck notification on three events -

MFTS C-pin alarm
MFTS R-pin alarm
Coolant level low (F66)

Extending the thought further, it would be easy to rig up a simple SPST switch to C and R pins so that the ECU goes into shall we say 'valet mode' or 'wife mode' or 'economy mode' if you wish to limit boost levels without raising alarms on the Autocheck.

Or you could have it full frontal as a 'sport mode' switch - when active ties the C and R pins together for maximum driver info (and boost), but when inactive has the R pin pulled to 0V with the C pin doing its normal Autocheck only thing - and you get mechanical boost control without any alarms (as opposed to diss'ing the WGFV).

Paul

[alg]

Excellent Paul Glad I asked. Can you confirm that the coolant temperature alarms to the ecu from the G62 coolant temperature sensor and MFTS put the car into low boost (0.4 bar) or do not.
What I am driving at is a faulty MFTS will cause fixed low boost/limp mode/WG spring/0.4 bar and/or false coolant autocheck alerts and/or dash coolant gauge non functioning ONLY
Not the miriad of faults that claim to have been solved by its replacement

[S2central.net]

AFAIK - its only the MFTS (F76) R pin that trigger that safety mode on the S2/RS2.

The G62 sensor gives raw water temp information to the ECU. In the event of G62 failure then ECU uses air temp info to derive substitute values based on some pretty simple algorithm.

G62 is just an NTC resistor - its not a thermal switch like the C and R pins on the MFTS.

HTH


Paul

[UrS4boy]

Good on you Paul. You obviously know your way around the electronics of S2s, etc. Nice trick with the two pins. Also, nice extension thought of using those pins to create a "valet" mode (you can also pull the WGFV connector to do that but a nice switch would be cleaner/easier to use).

Now, if you could just figure out whatzup with the AAN version of the three pin MFTS and why it doesn't (or secretly does) connect to the ECU like the 3B before it and the ABY after it.

Not that I am worried. I live in Vancouver BC and it rarely gets hot enough to even get the afterun pump to come on after a drive.

[S2central.net]

To clarify - there is no 'AAN version of the three pin MFTS' -

The MFTS is common to us all - there is the old 4-pin active variant and the newer 3-pin passive variant. The signals on the T, C and R pins are identical.

It just seems that the AAN ECU doesn't get fed the R-pin. It doesn't show up on the AAN schematic. Nor does it on the 3B though !!!

Have you actually buzzed this out on the AAN youself to be certain ?
I don't have the AAN schematics under my nose right now, but if you measure voltage at the MFTS-R pin with the ECU connected and ignition on we can learn something.

Paul

[UrS4boy]

To clarify - there is no 'AAN version of the three pin MFTS' -

Paul

To be clear, I have family album and am familiar with Scott Mockry's website and description of the two types of MFTS. I know there isn't a special "AAN MFTS". What I meant was the "special" way that the AAN seems to not involve the MFTS other than as a water temp gauge driver. I suspect that it actually might be connected to the ECU, but, as I suggested, don't really care. It never gets hot enough here to worry about temps limiting boost. (Of course, IF I tracked my car, the heavy pig that it is, I might change my tune on being interested).

[alg]

AFAIK - its only the MFTS (F76) R pin that trigger that safety mode on the S2/RS2.

The G62 sensor gives raw water temp information to the ECU. In the event of G62 failure then ECU uses air temp info to derive substitute values based on some pretty simple algorithm.

G62 is just an NTC resistor - its not a thermal switch like the C and R pins on the MFTS.

HTH


Paul

Thanks Paul. I will go replace my G62 and lambda to see if my Xs fuelling issues can be resolved (only code was lambda adaptation exceeded)
Air intake sensor replaced last year.
I will stick with my old active 4 pin MFTS for now as no codes relate to it and boost is fine.

[S2central.net]

Stop suspecting and whip out a voltmeter so we can close this thread !

[alg]

OK OK I will get one. I have only just started to do my own work on the car. Any suggestions about how to read the resistance across the G62 without being a double jointed long thin type of person

[S2central.net]

Right - forget this link idea between the C and R pins for now... Sorry to say I was focussed on the R pin behaviour and not what the AUtocheck does with C pin.

The C pin is held at ~1V by the Autocheck modules - which brings it below the threshold where the ECU thinks there is an alarm and boost control is disabled.

Sorry fro the delay in discovering this - I was away all day yesterday. I have removed the link in the T8f connector and need to rethink another way of doing this. Quite why the Autocheck module doesn't run this pin at 5V I'll never know - thats the problem with assumptions and trying to do things in 5 minutes

Paul

[sal_s2]

Is the T pin for the temp display on the clocks?
Doesnt the ecu take its info from the temp sender on the back of the head?