1988 Check Engine Light

You need a super duper high tech code retrieval tool, A paper clip, jump terminals A and B on the diagnostic connector under the dash then turn the key to the run position but don't start. Service Engine Soon light will start flashing stored codes starting with 12, which means the ECM passed its self test.. It will flash each code three times and then go to the next. Jumping the terminals while the engine is running is how to find out if the system is in open loop or closed loop. In open loop it flashes fast, 2.5 per second, in closed it flashes slow, 1 per sec.

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