I was curious about this...if the SES light doesn't come on, does this mean there are no codes stored in the ECM? I've been having trouble with the car lately, but the SES light never comes on. I think my ECM's working cuz the light came on when I disconnected my distributor-ECM harness to time the car.

Will the car store codes and just not turn the SES light on?

Mark

 

the light always comes on when the code is first read. after that it is stored in memory but the light may not stay on. you can have up to 50 codes i believe stored in memory at once - just disconnect the batt to clear them.

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89 Iroc-Z LB9 305 TPI auto 2.73 posi:
3" Dynomax "cat" back,K&N filters, TB bypass, 3" pipe in place of cat, cleaned and flow-matched injectors, 180' thermo, mild ignition mods, synthetic oil, kicker sound system, soon to attempt engine swap...

 

Squirrel,

It is possible to have error codes (DTCs) without setting the SES (MIL) lamp on. Soem codes are considered secondary, or minor, and do not necessarily set the MIL lamp.

IROC is somewhat correct. There is a limit to the stored codes. There is no numerical limit below the number of possible codes, but DTCs will be retained in RAM for the last 50 engine starts.

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Later,
Vader
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"No matter how hard you try you can't stop us now"
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