Hi All,

I'm in need of technical help: my early '04 DB9 (number 311 off the productionline, September 2004) recently started to dissengage the Automatic gearbox for no reason at all and throwing the .."GEARBOX FAULT SERVICE REQUIRED”.. message. First thing I did was replace the battery but that did not change the problem. I was able sometimes (with no logic at all) to 'reset the fault for a couple of miles but since It has been more persistent without the chance to reset the problem.

With the battery out of the occasion I hooked up my Autel once more and it showed code P0705

This lead me to Aston Martin Service Bulletin SB-19-0392V2: this is revision 2 of a bulletin which was published March '15 and basically covers a ground cable modification to sort this matter. Attached a copy of this bulletin.

In brief: The ground cable modification makes sure the correct wire resistance is restored by means of putting an additonal wire from the PCM module (underneath the
right front fender)



Into the cabin and hooking this up into the 'top level assembly" i.e. the facia unit (Radio, AC unit etc).



Problems I face now are:

1) the Bulleting speaks of a single black/purple wire which is mounted into plug C0634 (one of 3) on terminal 41. On page 21 of attached bulleting under step 72 it shows a white plug. The onces I have on my car (all three that go into the PCM) are all black and also neither of them show a number C0634 or anything close. The plug does appear to be similar in terms of rows, layout etc. Also, out of the three (3) black plugs, two (2) have both a black/purple wire from both their terminal 41.. I have therefore (while at it) pulled 2 wires into the cabin, just being sure that I can measure resistance from either cable individullly and connect the right one, leaving the other one unused

While taking the facia out of my car I noticed that the plug described in the SB under step 112 shows to have three (3) rows of wires while the plug I have in my car only has two (2)... furthermore, pin 8 in that plug is supposed to have the black/purple wire but no such wire is visible, nor in any other plug in that particular area.


I then noticed "trial" on the facia backframe assembly. Given the fact this car is an early run DB9, could the car be equipped with a trial/early version loom which obviously then mis-match the SB version?



Taking resistance measurements doesn't give me clarity either. The last thing I wanna do is fry up my PCM or anything else on the car. I checked the main loom running thru the car (to the back) for a black/purple wire but its also not present there.

I've tried to find the original Service Bulletin which perhaps indicates different colours but can't find a copy of that or anything.

Is there anyone here that can shed light on this?

 

I can understand why they wanted to run this ground wire... They are relying on the body of the car to provide the ground and they have some ohmic loss/difference between the interior ground point and the engine compartment. Drives Electrical Engineers nuts as it shows as ground on the drawing... And the current draw for the PCM probably has some high frequency components. But enough EE geezing...

I found that looking at Ebay and wiring harnesses to be very helpful when trying to figure out what I owned: Here's a cabin harness: https://www.ebay.com/itm/Dashboard-P...temCondition=4 from an 07. Does it look like yours?

I can't help you otherwise, but in general the color of the wires should be consistent, and I could easily imagine splicing grounds to get continuity. And, I'd likely use at least 14 gauge wire if I was going to make the effort to show a wire through the access hole in the fire wall.

 

Post the SB so we can better understand your issues.

 

Apologies, did mention it in the write up but forgot to upload. See attached..

 

Do you have the connector numbers for the ones in your photos? If so, post those numbers.

 

Thanks for guiding me to this loom: it does look fairly similar indeed but appears to be for a LHD car; the sticker tag statse RO LHD. Mine is RHD... Not sure what the differences are.

 

Below picture of the three (3) connecters with their respective numbers 3295, 2124 and 3477



These are the 'same' connecters coming from the loom as pictured in the Service Bulletin, figure 82 on page 29 with the big difference being the 3row vs. 2row pins in my car... I can also see no other connecters in that area that I may have overlooked.

 

The wiring changed in 09MY so your plugs are different to that shown in the SB. The C0430-8 black/purple wire on post 09MY vehicles is a PRND ground that goes to the signal return connection (C0636-41) on the ECU. But on pre 09MY vehicles pin C0430-8 should be white/black wire going to the Aircon recirculation switch.



Colin......

 

Hi Colin,

This is very helpfull and clarifies. Now, pin 8 on the connecter indeeds holds the white/black wire. AM I still to connect it to the black/purple wire on terminal pin 41 as per SB (see figure 58, page 21) or do I need to find the white/black wire on my pre 09 plugs? Do you perhaps have a PDF of these plugs as well?

Thank you big time!

 

I’m assuming as AM4884 previously stated that the aim of the SB is to ensure a good ground for the PRND switch pack. From what I can make out from the wiring diagram the ground for the Auto switches on your DB9 come from a different connector, C2737-20.

Unfortunately I haven’t got reference for where this connector is located but it shouldn’t be too hard to find by cross referencing the wire colours. The location of C0634 is shown in the attached.

Colin....

 

I spent time looking at this too. I agree that you want to connect C0634-41 B/P to C2737-20 B/P. You need to look for a connector in the console area near the trans push buttons with a B/P wire. The connector numbers in your photo I could not find anywhere on my schematic, which covers DB9 from VIN 0001. BTW, are the connector numbers referring to the connector on the unit side or the harness side? Are there numbers on the back side of the trans push buttons or wherever those three connectors in your hand mate to? Just want to make sure there is not another set of connector numbers on the other half.

 

I believe C2737 is the plug that connects to the Switch-By-Wire module, but I’m not sure of its exact location, possibly somewhere behind the centre console.

 

The numbers molded into the plastic are most likely related to the manufacturer part number for the connector itself and not to the numbering scheme in the schematics.

The connectors will be some industry standard part used in lots of different things and not something made special for AM.

 

Thanks both gents. I found this unit stacked in the mid-console just between the Volvo CD-player and PRND buttons. The blue/purple wire was easily spotted on the connecter and when checking resistance between the wire-connection on the plug to the two (2) yellow wires I previously connected onto my PCM's plugs (not knowing back then which plug, hence I connected both black/purple wires individually) one wire produced the satisfying beep sound. It's soldered and taped all up.

I'm now trying to reset the P0705 code with my Autel thru the OBD port but that has yet to prove itself working......

(if you have any suggestions which Ford or Volvo path to use, please chime in)

 

I remember that I used XC90 to reset my SRS code on the body port. Is the trans on the OBD or Body port?