After reading the instructions of clearing codes in a Volvo manual, learning from this forum, and visiting other sites, it seems a number of points need mentioning regarding this important lamp. First, the manual simply say that any fault related to the emmisions will trigger the lamp. Service manuals also mention that about a dozen faults with the transmission will also cause the lamp to come on including faults found with the fuel system and/or ignition. The question posted time and time agian however is how do we turn it off? Unlike the service lamp which is simply a "reminder" indicator that we can turn off using test mode #4, the "check engine" lamp, which BTW Volvo refers to as the "MIL" (malfunction indicator lamp),uses test mode #1, requires all the codes to be erased first thus inturn resetting the lamp. Time and time again the instructions seems to point to the A2 (fuel) DLC for clearing codes, with job now complete. My conclusion is that this may not be enough and that A1 (transmission) may be the culprit and/or A7 (combined instruments) may be the cause. In any case, if one of these don't do the job, then we need to try clearing codes elswhere. Can anyone else confirm or deny my conclusion? Nowhere in the archives could I find "turning off check engine lamp - '93 - '95 850". This would be valuable information to be included.