MikeShields

I have a 1991 300 SL on which the Check Engine Light just started coming on (not on cold start fwiw but always after a few minutes or running or when warm starting).

I Jury rigged an OBD 1 flash counter for the 16 pole diagnostic connector and using Pin 1 as the momentary connection counted these results:

Pin 3 & Pin 8 = 17 flashes then if done again 22 flashes

Pin 3 & Pin 13 = 17 flashes then if done again 22 flashes

I've downloaded the Baum tools CS1000 Instructions which I think reports
8-17 = Crankshaft position sensor faulty
8-22 = O2 sensor voltage is too large.

but nothing for 13-17 nor 13-22.

Suggestions or directions to more clear diagnostics for the R129 would be much appreciated!