DIY: Highline CECM Swap
This document is for informational purposes only. Any vehicle modifications should be done by a certified VW mechanic. Neither the author nor this site will be held liable for actions taken resulting from the information set forth herein.
The retrofit should take you no more than one (1) hour. This DIY will show you how to swap out the central electronics control module (CECM). The reason for upgrading to a highline CECM from a lowline CECM include the ability to retrofit fog lights and HIDs appropriately as well as having a great pickup line at cocktail parties. This is what a CECM looks like:
The following links to Ross Tech’s website provide a comprehensive list of CECM part numbers and their high/lowline designations:
* Required tools. All others will just make your life a whole heck of a lot easier.
* VAG-COM and Hex+CAN cable
* Wrench 10 mm (to remove battery connector)
* T20 torx bit
Precision flathead screwdriver 2.5 mm or 3.0 mm
1. Go through each byte of your CECM (address 09) with VAG-COM and take note of each bit marked or unmarked. Best way is to just take an image capture or screenshot of each byte screen. This will allow you to go through each bit with the highline CECM and ensure that the long coding is precisely carried over.
2. Note the relay configuration of the highline CECM in case your stock configuration is in any way different (unlikely). Best way is to just snap a photo.
3. Pop the hood and disconnect the negative (-) battery cable using the 10 mm wrench.
4. Pry off the fuse box panel in the dash using the trim removal tool or flathead screwdriver.
5. Remove four (4) T20 screws in the footwell. The two (2) indicated in red will release the footwell plating and the two (2) indicated in blue (one outside of photo) will partly release the light switch / dimmer fascia.
6. With the footwell plating lowered, detach the footwell lighting harness and the OBD harness. The lighting harness is detached by squeezing on the sides and pulling out. The OBD harness is latched into place with one (1) hook on top and two (2) on the bottom. Use a small flathead screwdriver to unlatch the three (3) hooks.
7. Remove the light switch by pushing in; turning right (it will not turn much); and pulling out in one motion. Unlatch the light switch harness by pushing down on the clip and pulling out.
8. Remove the T20 screw inside the empty light switch socket inside the top portion of the socket.
9. The last T20 screw securing the light switch / dimmer fascia is located under the left end of the steering wheel trim lining the instrument cluster. Carefully pull on the trim to unlatch it and reveal the T20 screw. Unlock the steering wheel and adjust accordingly to provide more space to work in. Be careful with the latches – they can scratch your instrument cluster.
10. With the four (4) screws securing the light switch / dimmer fascia removed, you can proceed to carefully remove the entire fascia. Note the dimmer switch wiring harness which needs to be unlatched.
11. Dig the ghetto rear fog harness job. This is a prime example of how not to thread a rear fog harness.
12. The CECM is located underneath the dash just above the hood release lever. Two red levers need to be pulled towards the hood release lever to unlock the wiring harnesses for removal. See step #14 for where these red levers are situated.
13. There are eleven (11) wiring harnesses in all that need to be unlatched. The images below show the latching mechanisms (blue arrows) of some of the connectors as a guide. Ignore the violet / purple locking mechanisms – those are to lock the wires in place and has nothing to do with unlatching the connectors.
14. With all the wiring removed, only two (2) clips on each side of the CECM hold it into place. Simply depress these clips and ease the CECM out of its holding brackets. It will not just drop out – you may need to ease it out being careful that the relays are not knocked loose by the edge of the dash.
15. Insert the highline CECM into the holding brackets ensuring that the two (2) clips on either side has latched onto its edges.
16. Proceed to replace all eleven (11) wiring harnesses. It is nearly if not completely impossible to misplace a connector since they all appear to have a unique shape. The harnesses are also rather stiff and lengthened appropriately to their location. You can also refer to the old CECM for locations of particular connectors.
17. Proceed to re-install the light switch / dimmer fascia; then footwell plating; and ultimately the fuse box cover – in that order.
18. Reconnect the negative terminal of the battery.
19. As a precautionary measure, run through the CECM in Vag-Com and take note of every byte as you did in step #1. Then go through each byte and recode the CECM to your original coding. Note that certain bits may lack any descriptives. Check off these bits anyway as long as your original coding dictated. Clear any remaining fault codes.
20. Window and sunroof adaptation should be performed after every battery disconnect. Roll down each window and the sunroof all the way and then roll up each window. This will re-activate auto up/down and recalibrate pinch detection.
21. Drive a few meters in a straight line to perform steering adaptations and clear the remaining lights in your dash.
That's it. Doesn’t look like much from the outside but you’re ride is now a highline CECM sportin machine. No more ghetto hacks for you.
******* End of DIY *******
Thanks to maloosheck, 15DegreeJetta, Brickyward Imported Car Parts, and Ross-Tech.