Mercedes ECU A2661538879 | 5WK90957 | SIM266 | *Plug & Play* Exchange unit (Free Programming BY POST) – Unit supplied + Cloning service (Exchange unit)

1 .  Scan the vehicle with a diagnostic scanner & record fault codes – rectify any faults recorded here first & check the wiring for faults

2 – If your ECU has ‘No communication’ with a diagnostic scanner it is essential that you check relevant fuses and consult a wiring diagram for your vehicle and verify the power supply & test the wiring to your ECU – particularly test power supply relays (Engine control relay). – ECU’s returned due to misdiagnosis are subject to a 20% restocking charge

If you are not a qualified / experienced auto electrician or garage technician and you are unsure if the problem with your car is the ECU then please consult one first before ordering – there is a 20% restocking charge for returns due to misdiagnosis

If your fault is a cylinder misfire please check spark plugs / leads / coil / injectors and wiring faults / headgasket faults etc before ordering, if these have been checked or replaced then it is important to check inlet manifolds for leaks, engine compression & perform a vacuum gauge test to check for valve problems.