VR6 OBD2 Harness Adaptation

[science 0]

OK, I've just completed this swap and can see that its easy to get stuck, you should read the following guide before proceeding;

 

http://the-corrado.net/showthread.php?t=54148

 

and further reading available at;

http://www.corrado-club.ca/forum/viewtopic.php?t=5880

http://forums.vwvortex.com/showthread.php?3934082

http://mk2vr6.com/board/viewtopic.php?f=12&t=7831

 

The purpose of this guide is to supplement the previous guide only in adapting the harness from an OBD2 Golf to fit the Corrado as close to the factory look as possible. I've had to do this away from the car hence the method, measurements and notes below. I hope some of the information is of use if you are undertaking this swap.

I used a manual gearbox '95 Golf loom although other OBD2 looms will be different if they are from another model car or have an auto box and other auxiliary wiring.

Check your ECU part numbers here;

http://www.corrado-club.ca/tech/vwecucodes.htm

Anything Bosch Motronic 3.81 is OBD2.

 

Use or print off these very useful links for reference;

http://www.a2resource.com/electrical/CE2.html

http://www.a2resource.com/electrical/management/motronicvr6aba.html

http://www.clubgti.com/showthread.php?219775-Fusebox-FAQ

 

Things to consider;

 

TOOLS & TERMINALS;

It is possible to adapt the harness without cutting any wires if you use the de-pinning tools for Junior Power Timer connectors. If you intend to cut the redundant parts away from the harness, it's best to performing a trial run and make sure the car runs with the OBD2 loom before cutting.

 

I used the LASER 4328 Terminal Tool Set For Renault Citroën & More... for around £40. It covers Micro Timer, Junior power timer, Power timer and single spade plug covers. Plus 3 others types I've not used. I've tried loads of other terminal tools, even tried making my own, but this only kit to work reliably.

 

You can get the connections used in the fuse box from here;

http://www.polevolt.co.uk/acatalog/Terminals_for_Special_Applications.html

or here;

http://uk.rs-online.com/web/c/connectors/pcb-connectors/pcb-connector-contacts/?searchTerm=junior+power+timer

or of course eBay.

Although you may need “Uninsulated open barrel F crimp ratchet crimping pliers” (ebay)

 

Terminals used were;

Micro Timer II socket (female)

Junior Power Timer Tab (male)(there are two types, use the type which looks like a box at the wire end)

Junior Power Timer Socket (female)

Power Timer Socket (female)

6.3mm Female Spade

 

I also printed off a list of terminals (G1/01,G1/02,....ect) and used 6mm clear heat shrink to label any de-pinned wires I though I might loose track off or use pen and masking tape for a less permanent label.

 

LOOM FITMENT;

The Golf Loom is a slightly different shape to the Corrado if you want it to fit properly some wires will need to be shortened at the MAF, Carbon Canister valve, Lambda, Rear Knock Sensor and at the fusebox end. Make sure you have a terminal removal & a crimping tool and some Junior Power Timer & Standard Timer connectors. If you choose not to do this there will be excess loom particularly around the ECU.

 

AUX COOLANT PUMP;

In the Corrado Loom the Aux Coolant Pump runs through the 42 pin Engine Connector (T/42) on pin 31, then to the fusebox where it connects to wires leading to the Fan Control Module.

With the OBD2 Loom it runs straight (through pin 31 on T/42) to the Fan Control Module and is therefore too short.

The same is true for the trigger wire from Pin 3 of the yellow temperature sensor for the fans and aux coolant pump after run on pin 9 on T/42.

These two wires from T/42 will either need to be swapped from the Corrado loom, extended or replaced to reach the fusebox.

To replace from T/42 to fusebox you will need;

2x Micro Timer socket terminals for the T/42 connector

1x JPT tab (male) terminal for the Red/Black at the fusebox

1x 6.3mm Female Spade for the Brown/Red at the fusebox

and 2.12m of Brown/Red and 2.12m of Red/black 0.5mm thinwall cable.

Alternatively you could transfer the Fan Control Module and wiring from the Golf Loom if you have it. This is what I intended but the Golf loom only had a 2 speed fan controller not the 3 speed one like Corrado loom does. Otherwise the Fan controller loom takes a live feed from A1/05 for the fan thermoswitch and a couple of earth wires and a battery live connection.

 

MFA AMBIENT AIR TEMPERATURE SENSOR;

Some OBD2 looms don't have this. If so either keep this section of your OBD1 loom or make a new one.

1x 2way Female JPT Housing

4x Junior Power Timer Socket (2 for fusebox, 2 for JPT housing)

2.10m of Brown/White & 2.10m White/Red 0.5mm thinwall.

 

AIR CONDITIONING (ON) SWITCH;

Some OBD2 looms don't have this. If so either keep this section of your OBD1 loom or make a new one.

2x Micro Timer Socket terminals

2m of Green & 2m Blue/Red 1mm thinwall

 

LAMBDA POWER WIRE;

On the Corrado, this runs through a relay (Type 53), but with OBD2 it runs straight from G1/08 which on my new loom was shorter, so I replaced it with;

2x Junior Power Timer Socket

1.7m of Red/White 1mm thinwall

 

CHECK BOTH LOOMS;

Before starting it's best to check both looms. I've made a spreadsheet from the links above to compare the Corrado and Golf Main wiring plugs, for the conversion we are concerned with Plugs F,G1,G2 and S.

[ATTACH]78936[/ATTACH]

 

The other wires to identify on the OBD2 loom are;

Data Line Grey/White wire from ECU pin 43

Vehicle speed sensor (VSS) Blue/White wire from ECU pin 65

MFA MPG Violet/White wire from ECU pin 51

Injector Power (Yellow Plug) thick Red/Blue wire

and if present;

AC (On) Switch Green & Blue/Red wires from ECU pins 37 & 39

 

If you have all the necessary wires in the right place and the loom does not appear to be damaged, continue...

 

1-REMOVING THE OLD HARNESS;

Starting at the fusebox unplug the following (the two yellow plugs may not be connected);

 

Fuse Box Connectors with Female Junior power timer connectors unless stated;

F – (White Plug) 10 Pin- Engine Harness Near Gearbox

G1 - (White Plug) 12 Pin- Engine Harness Engine Sensors

G2 - (White Plug) 12 Pin- Engine Harness Engine Sensors

S- (White Plug) 5 Pin- Wiper Motor Harness

Lambda Relay 4 Pin Female Spade Connectors

Data Line (Brown Plug) 2 Pin- Data Line Yellow & Grey/White wires

Vehicle speed sensor (VSS) (Blue Plug)1 Pin- Blue/White wire

MFA MPG (Black Plug) 1 Pin- Violet/White wire

AC (on) Switch (Yellow Plug) 2 Pin Male JPT-Green & Blue/Red wires

Z- (Red Plug) 1 Pin Red/Yellow wire

Aux Coolant pump (Red Plug) 1 Pin Male JPT- Red/Black wire

Yellow Temp Pin 3 (White Plug) 1 Pin Female Spade Connector – Brown/Red wire

(Yellow Plug) 1 Pin- Yellow/Black wire not used, ends in a un-terminated wire near starter.

[ATTACH=CONFIG]78946[/ATTACH][ATTACH=CONFIG]78947[/ATTACH][ATTACH=CONFIG]78948[/ATTACH][ATTACH=CONFIG]78949[/ATTACH][ATTACH=CONFIG]78950[/ATTACH][ATTACH=CONFIG]78937[/ATTACH][ATTACH=CONFIG]78938[/ATTACH][ATTACH=CONFIG]78939[/ATTACH][ATTACH=CONFIG]78940[/ATTACH][ATTACH=CONFIG]78941[/ATTACH][ATTACH=CONFIG]78942[/ATTACH][ATTACH=CONFIG]78943[/ATTACH][ATTACH=CONFIG]78944[/ATTACH][ATTACH=CONFIG]78945[/ATTACH]

Some of the connectors will be needed for the OBD2 loom.

[ATTACH=CONFIG]78933[/ATTACH]

 

2-ENGINE BAY

Working you way around the engine bay, unplug;

 

The wiper harness connected at the wiper motor and push out the grommet, save this and the grommet its going back in later.

 

Lambda 4 Pin Connector

Rear Knock Sensor 3 Pin Connector

 

MAF sensor 4/5 Pin connector

Carbon canister valve 2 Pin

Ambient air temp sensor 2 Pin, keep this if your new loom doesn't have one.

 

68 Pin ECU plug

 

42 Pin Engine Twist Lock connector

 

Starter 1 Pin Red/Black

Front Knock Sensor 3 Pin

Crank Position Sensor ;3 Pin

Alternator exciter 1 Pin Blue Wire

Reverse Switch 2 Pin

 

 

3-GROMMETS

 

If you de-pin the larger fusebox connectors (F,G1,G2,S) you can use the Corrado bulkhead grommet, the Golf grommet is too big. If you use the Golf wiper loom note the wire colours are different but the connections remain the same. Also keep the small grommet on the wiper motor harness.

The ECU Grommet is not so easy, I built up some self amalgamating tape to fit the hole, otherwise find a replacement 50mm grommet or cut and glue the old grommet onto the new loom.

On the Corrado Loom there is a grommet on the T/42 connector this won't be on the new loom. If you wanted to use one the part numbers are 1H0971840A for the grommet & 1H0973132A for the retaining ring but it would require all terminals to be removed from T/42

 

4-CORRADO LOOM DIMENSIONS

If you want the new loom to fit the same, you can measure up the old loom; or use the diagram below.

 

FUSEBOX
CONNECTORS
|
|
|
0.4m
|
|
|
BULKHEAD
GROMMET
|
|
|
0.26m
|
|
|
|----0.97m----|---0.15m----[ LAMBDA SENSOR ]
|             |
|             |----0.17m----[ REAR KNOCK SENSOR ]
(0m)
|
|
|----0.97m----|----0.10m----[ MAF ]
|             |
|             |----0.25m----[ CARBON CANISTER VALVE ]
|
0.60m
|
|
|
|----0.22m----I ECU GROMMET I----0.17m---[ ECU PLUG ]
|
|
|
0.48m
|
|
|
|----0.47m----[ ENGINE TWIST CONNECTOR ]
|
|
|
|----0.58m----|----0.14m----[ STARTER ]
              |
              |----0.15m----[ ALTERNATOR EXCITER ]
              |
              |----0.17m----[ FRONT KNOCK SENSOR ]
              |
              |----0.17m----[ REVERSE SWITCH ]
              |
              |----0.18m----[ CRANK POSITION SENSOR ]

[science 0]

ADAPTING THE NEW HARNESS

1-Unwrap the OBD2 loom being especially careful where it branches off as there are thin wires that can accidentally be cut if using a knife.

The sections of the loom which can stay wrapped are;

The last 39cm nearest the ECU

The last 58cm before the front engine harness connectors branches off by the starter motor.

and if not replacing the aux pump wires, the last 47cm nearest the T/42 engine connector.

 

Once unwrapped its easy to see the wires that do not connect to either F, G1, G2, ECU, or T/42.

At the fuse box end, you should be able to identify the plugs needed (equivalent to the Corrado loom);

(i) F plug should have 4 wires in it, the other end of which terminate near the starter motor.

(ii) G1 & G2 cover feeds to ECU and Engine and Sensor return paths to dash.

(iii) ECU and T/42 plug contain all the other wires needed to run the ECU and Engine.

(iv) Data Line Grey/White wire to ECU pin 43

(v) Vehicle speed sensor (VSS) Blue/White wire to ECU pin 65

(vi) MFA MPG Violet/White wire to ECU pin 51

and if present;

(vii) Injector Power Thick Blue/Red wire

(viii) AC (On) Switch Green & Blue/Red wires to ECU pins 37 & 39

There was no Air Conditioning on my loom so ECU pins 37 & 39 we're not used

[ATTACH=CONFIG]78952[/ATTACH]

 

All other wires are not necessary or are contained in separate looms on the Corrado. In the Golf, VW chose to combine and wrap these other looms with the engine loom although they are not physically connected.

 

2-Remove all wiring from the loom that does not connect to plugs F, G1, G2, the ECU, or 42 Pin connector. If you are cutting wires to remove them, test fit and run the loom on the car first.

 

There will be loads of extra wiring which isn't used. Most of it is the lighting circuits and radiator fan but it could also have indicators, washer jet heaters, headlight level adjusters, coolant level, battery strap, etc.

You will probably find plugs A1,A2,C and an assortment of other plugs but as long as none of the wires go to the ECU or T/42 they can be removed.

 

I also found it easier de-pin and label the wires from the plug F, as they would have become tangled while trying to remove unnecessary wiring.

 

Plugs that have wires that terminate at the ECU can be saved and de-pinned if needed. On my Golf loom this consisted of a 3 pin black plug that had the MFA MPG Violet/White wire in pin 3 so I de-pinned the plug so I could remove the other two wires.

 

I have a second Golf loom which has a 12 pin connector, with 3 wires going to the ECU

The 12 pin connector listed as central locking control unit;

Pinout for the one I have is (need to check later) something like;

 

1 Grey/Green + Green/Blue

2 Not Used

3 Black

4 Red/Black

5 Black/Yellow

6 Not Used

7 Green/Red + Green/Brown

8 Yellow/Red + Green/Grey

9 Blue/Yellow

10 Not Used

11 Brown/Black

12 Black/Red

ECU Pins 37&39 for air con and pin 54 for ECU power connect here but I'm not sure where just yet I don't have the loom to hand.

 

3-Fit new or extend wiring to Aux pump and Yellow temp sensor, pins 9 and 31 on T/42 or replace with your old Corrado wiring.

[ATTACH=CONFIG]78953[/ATTACH][ATTACH=CONFIG]78954[/ATTACH]

4-If your new loom does not have outside temp sensor, use the one from your Corrado wiring or make new one connect it to;

G1/02 Brown/White - mfa outside temp sensor pin 1

and G2/02 White/Red - mfa outside temp sensor pin 2

 

5- Reshape new loom working back from the Ecu and engine T/42 connector using your measurements or following the diagram above. Use insulating tape to keep the shape. Test fit on the car or compare to your old loom if your are unsure of the measurements. Do not untwist the Brown and Blue MAF wires.

 

6-Run a new Lambda power wire if needed.

 

7-Replace fusebox bulkhead grommet onto new loom. (Thin end first, big end nearest fusebox connectors)

 

8-Terminals and connectors at the fusebox end that are missing from the new loom can be replaced with the Corrado ones.

Brown Data Link Connector will need to be swapped

Red male JPT from the Aux Coolant Pump

White female spade cover from the yellow temperature sensor pin 3

MPG plug with the Male JPT tab will need swapping from the Black 3 pin plug to the Black 1 pin plug.

 

 

9-On my loom the ECU(pin1) and Engine bay loom(T42 pin 36) are earths which have ring terminals near the battery these will need to be connected onto the battery clamp when fitting back on the car.

 

10-Once your are happy with the shape of the loom wrap in fleece/fabric or self-amalgamating tape.

I used a combination of Coroplast fleece tape with self amalgamating tape at wire terminations to stop it from coming unraveled.

 

11-Trim wires and re-terminate wires which are too long to the correct length.

 

12-Re-Fit the adapted loom to car, and connect the injector power wire, thick Red/Blue with the Yellow connector to Z1, Remove Relay 109 and it should start.

Edited June 14, 2014 by science

[easypops 8]

Great wtite up mate, very detailed. My corrado is sorn'd at the moment and i have all the stuff(hopefully working as i never heard the donor running)lying in the garage to do this swap. But i have to say it's fairly daunting and i'm thinking i might kill the car if i start this :lol:

 

Are you thinking of doing this for others? :profileleft::idea::lol:

[fla 9]

Fantastically detailed, many thanks. Worth printing out whilst the loom is prepared. I've bought another loom which is more or less done and this will be a great help.

[fla 9]

On the red connector on the back of the behind the relay panel (30B Z1, Z2), does it matter where the leads are connected into the 'main' collective connector, or are they all bridged?

[science 0]

The connectors all have tabs which only fit the fuse box in the right location.

Only 30 and 30b are bridged with the 4 terminal red busbar, (whether they are also bridged inside the fuse box, I don't know.)

Z1&Z2 are elsewhere;

[ATTACH=CONFIG]79169[/ATTACH]

-Z1 Injector Power at the top of the image.

-Z2 Battery Ground at the bottom of the image.

The fusebox here is upside-down to its orientation in the car.

[Vaderizm 10]

I'm currently doing the OBD 2 adaptation as well and have come across somewhat of a problem. I have already installed the new harness, connected all the proper wiring, installed the proper ECU, but I have no Fuel Pump activity whatsoever... I read somewhere that the fuel pump relay may not be receiving a ground on the new harness. I went ahead and checked all my grounds and saw no issues. Any suggestions?

[science 0]

I'm currently doing the OBD 2 adaptation as well and have come across somewhat of a problem. I have already installed the new harness, connected all the proper wiring, installed the proper ECU, but I have no Fuel Pump activity whatsoever... I read somewhere that the fuel pump relay may not be receiving a ground on the new harness. I went ahead and checked all my grounds and saw no issues. Any suggestions?

 

OK, just a couple of quick checks;

Have you removed relay 109?

Does your ECU have the immobiliser removed?

Are fusebox pins 30 and 30b bridged?

Is fuse 18 blown?

Do you have have earth to brown wire in M/01?

Do you have power while cranking to red/yellow wire in M/02?

[fla 9]

http://the-corrado.net/attachment.php?attachmentid=78945&d=1402777375&thumb=1

 

This pin 3 wire from the yellow temp sensor - where does this go to in the engine bay?

[science 0]

http://the-corrado.net/attachment.php?attachmentid=78945&d=1402777375&thumb=1

 

This pin 3 wire from the yellow temp sensor - where does this go to in the engine bay?

 

pin 9 on T/42.

[ATTACH=CONFIG]79335[/ATTACH]

Edited July 24, 2014 by science

[fla 9]

Thanks for that. I didn't have it as a loose wire on my obd1 loom buf will check if pin 9 is occupied.

[Bruno 4]

I've got two looms ready to make up into one,  off the car. My first question is based on Dennis' old Canadian notes where he stated that the OBD2 system needed a second lambda probe, finishing with one before the cat, and one after it. Does that not mean that one needs to drill, tap and weld on a socket for the second lambda probe? Cant seem to find the original Canada guide online now. The vwvortex one is definately not clear.

[tonedef 8]

Only one lambda probe on mine, post cat. It’s not the same at the original OBD1 probe though, bought it new from VW at the time, sure I can locate the paperwork for a p/n if you need it?

[Bruno 4]

YES PLEASE! I've scanned about and found this part number - 021906256AK- but it needs confirming. 

Interesting that ours only uses one lambda sensor. On Saabs, which have pre-and post-cat sensors, the early one is used for short term trim, the second one is used for long term trim. They contribute to different parts of the maps.  

Had a gander under the car and from what I can see the original lambda probe seems to be just after the flange, but before the cat actually starts on my existing OBD1 setup. Looking at the B4/MK3 cat - which seems to be part no 1H0131701TX - it has two lambda take off points, one before, one after the cat.  I presume that I must thus create a post cat position for that new probe and blank off the  original sensor point.  

[tonedef 8]

Sorry, not sure what happened there, was thinking pre and typed post... it’s definitely PRE-cat, just after the flange.

It is however p/n 021 906 265 AK. I paid £138.47 for one from TPS in 2014, I think next time I might risk one for around thirty five  quid from autodoc, it’s pretty easy to swap and I’d have change left for almost three more!

[Bruno 4]

Thank you.

Does anybody know if our ECUs can handle pre and post cat lambda probes? What does one have to do to enable that?

Edited December 20, 2020 by Bruno

[Philly-R6 0]

On 6/14/2014 at 9:54 PM, science said:

you should read the following guide before proceeding;

http://the-corrado.net/showthread.php?t=54148

 Updated link:

How to fit / wire / install obd2 - [Archive] Wiki Submissions & Collaboration - The Corrado Forum (the-corrado.net)

[fla 9]

5 hours ago, Philly-R6 said:

 Updated link:

How to fit / wire / install obd2 - [Archive] Wiki Submissions & Collaboration - The Corrado Forum (the-corrado.net)

great stuff Philly!  I've forgotten a lot of what i did on mine - its good to look back at that guide.