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Diagnostic Systems for the 1993-1995 Mazda 626 MECS-II (1981-1995) All Models (except 93-95 2.0L automatics) EEC-IV (1993-1995) 2.0L Automatics Only OBD-II (1996-2002) All Models (Nothing in this topic applies to you, get an OBD-II code scanner) This article covers both MECS-II (OBD-I) & EEC-IV diagnostics for 1993-1995 Mazda 626, Mazda MX-6, Ford Probe, and other vehicles. You will need to figure out if you have either MECS-II or EEC-IV to get the most out of this article. Short history of OBD-I diagnostic systems: OBD-I is a generic term given to any diagnostic system prior to 1996's introduction of OBD-II. OBD-I is a blanket term and not an industry standard set of codes like we see with OBD-II. MECS-II is considered OBD-I, EEC-IV is also considered OBD-I. which is why we have to specify the difference in methods. Just because your car is OBD-I doesn't mean you'll use the same diagnostic system as an OBD-I BMW, Toyota, or Honda. Each manufacturer had their own OBD-I system. Mazda used MECS-II and Ford's EEC-IV system. Error codes are deciphered through a series of blinking check engine light (CEL) also known as a malfunction indicator lamp (MIL). It is comparable to morse code coming from the check engine light while the car is in diagnostic mode. Both EEC-IV and MECS-II can be checked using your engine's CEL/MIL light with exception to some 1993 versions that might not have a check engine light. If you do not have a check engine light you will need to hook up a test lamp in order to see your CEL/MIL codes. EEC-IV cars have the added advantage of using EEC-IV code scanners such as the Equus 3143 or 3145.