Engine codes
Le Mans Master
Joined: Sep 2013
Posts: 6,192
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From: near the thumb in the mitten
OBD1 MIL comes on when code sets. Some codes will keep light on the entire key cycle. Light will be out on next key cycle until fault reoccurs. History code will be store for 30 cycles if same fault doesn't reoccur code will clear. Some codes will turn MIL on while fault is occurring and MIL will go out when condition isn't present during the same key cycle. If MIL comes on there should code set. GM didn't have current ECM codes with no light. FSM code description will include MIL operation.
OBD wasn't regulated like OBD2, so MIL operation can vary from manufacturer to manufacture.
OBD2 can have codes set with no MIL.
OBD wasn't regulated like OBD2, so MIL operation can vary from manufacturer to manufacture.
OBD2 can have codes set with no MIL.
