MM3 Tuner Help - DTC Codes

[Gatlin118391]

I keep getting DTC codes, but the engine light never comes on.

Does the MM3 tuner keep the light from coming on?

I hate checking for codes once a month when the engine light should tell me there’s a problem.


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[Corkey]

After a few startup cycles, the CEL should pop up, indicating a hard code.

The MM3 will not enable the CEL "as far as I know."

If its periodic code, I don't think it stores it as you have to check as you have been manually

I probably butchered this, but it's somewhere along those lines.

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[AK Bob]

What codes are you seeing?

Many trouble codes do not turn on the check engine light.

Some codes will cause the annoying chime to sound off, while others will do nothing.

I assume your check engine lights up and then goes out on each engine start cycle (self-test).

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[Gatlin118391]

At every start-up, it does a self-test (engine light).

I guess my codes weren’t that bad for the check engine light.

The only code I remember was P0533 which I already fixed.

It was just a lousy pressure sensor.


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[AK Bob]

At every start-up, it does a self-test (engine light).

I guess my codes weren’t that bad for the check engine light.

The only code I remember was P0533 which I already fixed.

It was just a lousy pressure sensor.

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Yes, that trouble code does not set a check engine light.

See theory of operation in attachment.

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