I just bought the Autel ML629 reader, and I really like it. I bought it to diagnose a persistent SRS light on my sister's '03 ML350. I knew there would be at least two codes, because both rear seats are removed (therefore the rear seat belt sensors are disconnected). But the SRS light has been illuminated for about five years, apparently, and was illuminated well before the seats were recently removed.
Anyway, the Autel ML629 code reader works great! It pulled up the codes right away, and shows which were "stored" and which were "current & stored". There were six codes, including for various squibs and the driver's and passenger's seat belt buckles. I knew the front seat buckle codes were historic, because I recently tested those sensors and they were fine. The other codes (squib codes) were all labeled as "stored".
I reset the codes, and the only two that resurfaced were the rear seat buckle sensors (which, again, I know is correct because the seats are out). My next step tomorrow is to determine the "unplugged" resistance value on the rear seat belt receptacle (we have another ML that I can measure). Then, I'll make a little switch bypass circuit with a resistor, and hardwire that into each rear seat belt sensor, because my sister wants to have the rear seats out permanently. I have a circuit diagram for the SRS system, so I can see that the sensor circuit is a parallel circuit with a switch on one path (for when the seat belt is buckled) and a resistor on the other path (plus there is a resistor before the branching). So, I'm guessing it will work to just measure total resistance across the contacts of the receptacle side and replicate that on the other side (the sensor harness from the floor).
If I can figure that out, I'll post back with the sensor bypass information. As for the Autel ML629 -- it also can read the W163 Transmission codes, ABS, Traction Control, ESP, and emissions codes. I really like it! It works on other cars, too (though I haven't tried it yet). It was $106 on Amazon:
https://www.amazon.com/gp/product/B07D9ZPHV4/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1
Anyway, the Autel ML629 code reader works great! It pulled up the codes right away, and shows which were "stored" and which were "current & stored". There were six codes, including for various squibs and the driver's and passenger's seat belt buckles. I knew the front seat buckle codes were historic, because I recently tested those sensors and they were fine. The other codes (squib codes) were all labeled as "stored".
I reset the codes, and the only two that resurfaced were the rear seat buckle sensors (which, again, I know is correct because the seats are out). My next step tomorrow is to determine the "unplugged" resistance value on the rear seat belt receptacle (we have another ML that I can measure). Then, I'll make a little switch bypass circuit with a resistor, and hardwire that into each rear seat belt sensor, because my sister wants to have the rear seats out permanently. I have a circuit diagram for the SRS system, so I can see that the sensor circuit is a parallel circuit with a switch on one path (for when the seat belt is buckled) and a resistor on the other path (plus there is a resistor before the branching). So, I'm guessing it will work to just measure total resistance across the contacts of the receptacle side and replicate that on the other side (the sensor harness from the floor).
If I can figure that out, I'll post back with the sensor bypass information. As for the Autel ML629 -- it also can read the W163 Transmission codes, ABS, Traction Control, ESP, and emissions codes. I really like it! It works on other cars, too (though I haven't tried it yet). It was $106 on Amazon:
https://www.amazon.com/gp/product/B07D9ZPHV4/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1