ECU Loom Install Guide

 

 

Most 1.6 16v, 1.8T & 2.0 Petrol engines requires the additional ECU loom which we can supply on eBay; http://www.ebay.co.uk/itm/370782615559

 

 

The ECU-Bulkhead loom wiring is as follows:

 

Fitting the additional wires into the bulkhead connector plug

Once unplugged from the captive female socket in the bulkhead connection box, the black plug will look like this, with perhaps only 2 wires already installed:

Using a thumb or a screwdriver, push firmly on the end of the purple locking clip to slide it across into the released position, as shown below.

 

Take the 4 terminated wires of the supplementary wiring loom and insert into the following sockets as shown, ensuring that the receptacles are correctly oriented as per the pre-existing connections. Each terminal should 'click' home when fully inserted.

Once assembled, push back the locking clip to secure the terminals.

The connections are shown below for reference, and the wires that may already exist are listed for reference :

1 - Blue (OE colour Blue&Grey)

2 - Red (OE colour Red&Yellow)

3 - Black (OE colour Black&White)

4 - Red & Black

5 - White & Yellow

6 - (none)

7 - (none)

8 - (none)

9 - White

10 - (none)

Feed the supplementary loom out from the bulkhead connection box and alongside the main vehicle wiring up to the ECU. On my vehicle, the bulkhead connection box offered a spare outlet with a blank rubber grommet through which I fed the new loom.

On newer models there may not be this option as the bulkhead connection box uses a bolted down black plastic cover in place of the hinged lid. If this is the case on your vehicle, then drill an additional 10.0 mm diameter hole through the plastic cover next to the main loom exit grommet and make use of the sleeved grommet supplied with the new loom.

 

 

Fitting the additional wires into the ECU plug

The un-terminated ends of each of these 4 wires go to the larger of the two ECU connectors. The ECU is mounted under the middle of the windscreen, and is accessed via the engine bay once the scuttle panel is removed. Note that the vehicle battery must be disconnected before commencing this stage of the installation

To release the ECU plug from the ECU, reach behind the incoming loom to the plug and slide across the black 'T' shaped locking clip away from the connector towards the offside of the car. Once this has been released the plug can be pulled away from the ECU.

To remove the wires from the ECU connector, snip the cable tie and unclip the cover. Pull out the long pink retaining clip from the side of the connector, and pull upwards on the triangular separating piece that is between the two banks of connections.

It should now be possible to pull the two connector blocks, black and white, out of the housing. Each wire goes into the connector through the red rubber seal, then is crimped into barbed sections of the connector pin. 

Before fitting the new loom to the ECU plug, trim the length of the free wire ends so that the sleeving of the loom will cover the cables up to the ECU plug cover and leaves no coloured wires visible.

 

Note at this point that the ECU pin connection numbers for the CC loom are different between the different models. For 1.8T engines,  the connections to be made are as follows  

ECU Connections

LOOM COLOUR

OEM COLOUR

1.8T

BLACK

BLACK/WHITE

T121/38

RED

RED/YELLOW

T121/57

BLUE

BLUE/GREY

T121/75

WHITE

WHITE

T121/76

To insert the new connections, push the wire through the rubber seal and place it alongside the relevant pin. Next, use a medium sized flat screwdriver blade to push the new wire into the barbs of the connector pin.

Once the wire is pushed down, bend around the two retaining tabs at the top of the pin to hold the wire in place using a small flat bladed screwdriver.

Re assemble the connector and fit a new cable tie to hold the cover to the looms. Use additional cable ties to secure the CC loom to the existing wiring loom where necessary.

 

TIP - Now is a good time to recondition your wiper motor linkage before you refit the motor assembly to the car - the spindles that locate each wiper arm often seize up on Golf based models.

Refit the cover to the bulkhead connection box, refit the wiper motor and don’t forget to reconnect the wiring plug to the motor if you removed the motor completely. Refit the scuttle panel cover (easier if the pollen filter cover is fitted separately), and then the windscreen wiper arms.

 Before reconnecting the battery, turn the ignition switch to the on position to avoid any voltage spikes upsetting the airbag system. With the battery connected and ignition switched on, slide the cruise control switch to on and you should see the cruise control light illuminate on the instrument panel. Test drive and enjoy!