Mercedes-Benz SLK
2004–2011

Illustrative — for orientation only.

Location

RHD (UK): driver's footwell on the right-hand side, at the very bottom outer corner of the dashboard where the fascia rolls down towards the footwell, immediately above the bonnet release lever. Put your hand on the bonnet lever and lift straight up onto the underside of the dash and you are on it. The 16-pin socket faces downwards, so it is quicker to find by feel than by looking. LHD: mirror image — driver's footwell on the left, bottom outer corner of the dash between the steering column and the door aperture, again right beside the bonnet release and above the driver's left knee. Same position on every R171: SLK 200 Kompressor through SLK 55 AMG, pre-facelift and 2008 facelift alike. There is no second diagnostic socket anywhere on this car — the round 38-pin engine-bay connector belongs to the earlier R170 and does not appear on the R171, so if you cannot find the 16-pin socket in the footwell you are looking in the wrong place, not at an older protocol.

How to access

Small unmarked rectangular plastic flap, roughly the size of the connector itself, sitting flush in the underside of the dash trim. Hook a fingernail under the lower edge and pull it down — no tools, no trim removal. The 16-pin connector is angled downwards and is visible the moment the flap drops. Worth knowing before you start: everything reaches this socket through the EIS, which is the CAN B / CAN C gateway on this car, so if the EIS is dead or asleep you will get no OBD communication at all even though the socket and wiring are fine.