Cruise control fitting...

Words and pictures: Rob Bell

Well, unfortunately, I've not gotten too far due to the absence of the wiring loom - but here's what I've done so far...

1. Component parts first: cruise control interface
  Cruise interface mounting bracket
  Cruise control master switch
  Steering wheel switches (note that the cruise control switches come with replacement horns and ICE control switches...)
2. First step - disconnect the battery!
3. Next, open the glove box...

... and remove the retaining screws in along its top face (visible in picture opposite).

4. There are three screws to expose - one in each corner (as shown here), and one in the centre.
5. This is what it will look like after peeling back the carpet - it comes up with finger nails...

Now undo all three screws (unhelpfully, these are star bits - you may need to expand your tool selection here). The glove box will now just pull out...

6. But before removing completely, disconnect the glove box lamp.
7. Next, I screwed in the two cruise interface bracket retaining bolts in the front bulkhead - located to the right of the fuse box.
8. The bracket slots on...
9. And now tighten the bolts - and the bracket is held securely in place.
10. Now look for the cruise control wiring loom - it should be taped up with the main loom cables. This is where the wheels came of the wagon for me -it was no where to be found!

To enable identification, the connector in question is rectangular and black. The wires coming out of it are predominantly yellow! See detail below (the second colour statement in italics - where stated - is the wire's tracer colour):
Cruise interface unit (connector #C0895; 12-pin rectangular black plastic female connector, 2x6 pins):
Black, Red/light green, Light green/red, Yellow/black (x2), Yellow/brown, Yellow/black, blue/orange, Yellow/blue, and Brown (in pins 1 to 9 respectively).

11. To confirm the absence of the cruise control loom, I next turned my attention to the centre console. First I removed the trim panel (notice that my car has no optional switches here - which appears to predict the absence of the loom...)
12. Next, to make things easier to find the wiring loom - if present - I removed the in car entertainment system.

Note that there is plenty of space back there to fit a double DIN head unit... something I am rather tempted to do in the future!

13. Now remove the automatic climate control unit (ATC). Prise the fascia plate off using the edge of a credit card or similar. This exposes four philips screws. Undo these and the ATC pulls free.

There are a couple of wiring connections that need disconnecting before removing completely. Straightforward stuff.

The switch panel below simply unclips and pulls free.

14. I also went to the trouble of removing the ashtray/ drink holder unit below this (for installing cruise control, this is not necessary).

But doing so does reveal an interesting area of dashboard that you never usually see. And I could see no evidence of a cruise control loom!!! So I need to source one. The quest continues...

If there are switches taped up back there, the wire codes for the connector are as below (colour in italics is the wire's tracer colour):

Master switch (S124) (connector #C0749 black plastic; 6-pin female connector 2x3 pins): Black, Blue/orange, White/ blue plus instrument illumination - Red/white.

15. For completeness sake, I also removed the airbag from the steering wheel. This is inside the standard MG ZT steering wheel. Holes are already there for the retaining self-tappers for the cruise switches. A slot needs to be cut in the backing trim of the steering wheel boss to take the new switch though.

Take a template from the ICE switch aperture, and transfer this to the other side, and the job's a good 'un! No need to source a cruise-equipped steering wheel.

The wires in the steering column should be (colour in italics is the wire's tracer colour):

Steering column switch (rotary coupler, connector #C0082): Light green/red, Yellow/black (plus the standard wires for horn and ICE control).

For a summary of how the system connects up the various components, see figure below:

In this figure, we can see the various components that contribute to the cruise control. The key to the abbreviations used in this figure are below:
  • SWCS: Steering Wheel Control Switches
  • CCMS: Cruise Control Master Switch
  • IPK: Instrument Pack
  • CCIU: Cruise Control Interface Unit
  • ECU: Engine control Unit
  • CPS: Clutch pedal Position Sensor
  • BPS: Brake pedal Position Sensor
  • ABS: Anti-lock Braking System

The CCMS wiring is described in greater detail in the discussion above, and the CCIU wiring is more fully described below. In addition to these components, there are signal feeds from the ABS (which prevents cruise engagement if speed is below 21mph), and the signals from the two pedal position sensors (interestingly, there are two wires coming from the brake sensor - presumably so braking pressure can be determined?)

Brief description of wires to and from the CCIU:
  • Blue/orange is the on/off signal from the centre console cruise control master switch.
  • Light green/red and Yellow/black (pin4) is the feed from the steering wheel controls.
  • Yellow/brown and Yellow/black (pin 5) go to Header K109, connector C0294 (see below). These are the CAN bus signals to the ECU - the only cables not actually 'hard wired' between two components in the system.
  • Yellow/blue (not shown) is power from the engine compartment fuse box (fuse 4, 15A, connector C0575, pin 8 via Header K109, connector C0286, pins 5 and 6).
  • Brown is the tell-tail feed to instrument pack 'cruise activated' lamp; feeds via Header K109 (connector C0291 pins 11 and 13) to instrument pack connector C0230, pin 5.
  • Red/light green is output feed to the engine control module.
  • Black (not shown) - common ground via header K109, connector C0292 (pin 20).

Looking through the wiring diagram, I've put together this summary of connectors:

Connector code Location Description
C0749 Cruise control master switch in centre console Black female rectangular connector with 6 cavities and 5 wires (colours of wires described in text above)
C0895 Cruise control interface unit (CCIU), located behind glove box in fuse box compartment Black female rectangular connector with 12 cavities and 9 wires (colours of wires and function described in text above)
C0589 Passenger compartment fuse box (fuse 41, rated 10A) Connected to White/blue wire that feeds to cruise master switch
C0331 Engine control Module, engine bay Pins 23,24,27 and 28 connecting to cruise interface unit. Green/red (to clutch pedal), Green/purple (to brake pedal), Red/light green (to CCIU), and Purple/green (to brake pedal) respectively
C0603 Engine control module, engine bay Pin 9 - from engine bay fuse box (Black/pink)
C0286 Header K109 Pins 5 and 6 - Yellow/blue wire from engine bay fuse box and powers the CCIU
C0291 Header K109 Pins 11 and 13; brown wire from cruise interface unit to tell-tale lamp in instrument cluster (plug C230, pin 5)
C0294 Header K109 Pins 2 and 5; yellow/black and yellow/brown wires from CCIU.
C0082 Steering wheel rotary coupler (steering column) Pins 1, 4 and 5 relate to cruise control - Purple/black, Light green/red and Yellow/black respectively. The former is the power feed from the passenger fuse box (fuse 28, 15A) and the latter two are the signals to the CCIU.

That's it for now - will return to the task once I've sourced a cruise control loom (part number YMC104410)...