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BMW M5 F90 (2018+) General Forums Engine, Exhaust, Drivetrain, Tuning Modifications    Check engine light after catless primary downpipes

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      12-05-2019, 07:31 PM   #1
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Check engine light after catless primary downpipes

I had the dealership put catless primary down pipes yesterday on my M5 Competition. Next morning I had check engine light on. Took it back next day to BMW dealership. Mechanic said to get rid of the check engine light i needed a stage 2 tune. He recommended tune from DME. My question is, what if I do not want a tune? Check engine light a bad thing? Any harm to the engine, performance or anything? DME tune is $2400 stage two. That is steep. Any suggestions?
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      12-05-2019, 07:35 PM   #2
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Originally Posted by M5 dude now View Post
I had the dealership put catless primary down pipes yesterday on my M5 Competition. Next morning I had check engine light on. Took it back next day to BMW dealership. Mechanic said to get rid of the check engine light i needed a stage 2 tune. He recommended tune from DME. My question is, what if I do not want a tune? Check engine light a bad thing? Any harm to the engine, performance or anything? DME tune is $2400 stage two. That is steep. Any suggestions?
If you don't want a tune you'll have to live the CEL ... it's merely an annoyance and nothing else.
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      12-05-2019, 08:11 PM   #3
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I'm currently running KP primary/secondary combo, never had CEL after the install since I used a set of these O2 defoulers.

Since you've already had the downpipes installed, to avoid a trip back to the dealer you can easily install these yourself. Have a look at this thread to get a closer look at where they're supposed to go (2nd last pic).

Basically just unscrew both your post cat sensors, plug these in and install the sensors back on top. This can be done from the engine bay with the car on the ground, it's not a guaranteed fix but it did work for me and many others. Hope this helps and good luck!
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      12-09-2019, 10:30 AM   #4
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Quote:
Originally Posted by M5 dude now View Post
I had the dealership put catless primary down pipes yesterday on my M5 Competition. Next morning I had check engine light on. Took it back next day to BMW dealership. Mechanic said to get rid of the check engine light i needed a stage 2 tune. He recommended tune from DME. My question is, what if I do not want a tune? Check engine light a bad thing? Any harm to the engine, performance or anything? DME tune is $2400 stage two. That is steep. Any suggestions?

a BMW dealership installed catless DP'd for you? that's impressive in itself!
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      12-09-2019, 10:46 AM   #5
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Quote:
Originally Posted by M5 dude now View Post
I had the dealership put catless primary down pipes yesterday on my M5 Competition. Next morning I had check engine light on. Took it back next day to BMW dealership. Mechanic said to get rid of the check engine light i needed a stage 2 tune. He recommended tune from DME. My question is, what if I do not want a tune? Check engine light a bad thing? Any harm to the engine, performance or anything? DME tune is $2400 stage two. That is steep. Any suggestions?
you need a tune to hide it
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      12-09-2019, 06:37 PM   #6
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Quote:
Originally Posted by subzero05 View Post
Quote:
Originally Posted by M5 dude now View Post
I had the dealership put catless primary down pipes yesterday on my M5 Competition. Next morning I had check engine light on. Took it back next day to BMW dealership. Mechanic said to get rid of the check engine light i needed a stage 2 tune. He recommended tune from DME. My question is, what if I do not want a tune? Check engine light a bad thing? Any harm to the engine, performance or anything? DME tune is $2400 stage two. That is steep. Any suggestions?

a BMW dealership installed catless DP'd for you? that's impressive in itself!
Considering legislation.... omg haha. Man that's like saying a cow can fly. You'd have to see it to believe it. Must have been the tech doing a side job at the shop.
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      12-13-2019, 06:43 AM   #7
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You can get a tune without getting a tune just deleting the o2 sensors in the new flash.

Puting o2 spacers is not a good choice as the engines ecu reads false readings from post cat o2 sensors and may do unwanted corrections.
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      12-13-2019, 09:49 AM   #8
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Considering legislation.... omg haha. Man that's like saying a cow can fly. You'd have to see it to believe it. Must have been the tech doing a side job at the shop.
Right!!!
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      12-23-2019, 01:10 PM   #9
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Quote:
Originally Posted by M5 dude now View Post
I had the dealership put catless primary down pipes yesterday on my M5 Competition. Next morning I had check engine light on. Took it back next day to BMW dealership. Mechanic said to get rid of the check engine light i needed a stage 2 tune. He recommended tune from DME. My question is, what if I do not want a tune? Check engine light a bad thing? Any harm to the engine, performance or anything? DME tune is $2400 stage two. That is steep. Any suggestions?
i have mini cats on my o2's i bought from turner motorsports.

full catless for 4,000 miles now, still no CEL.

only jb4. no flash or stacks
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      12-23-2019, 01:11 PM   #10
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Quote:
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Quote:
Originally Posted by M5 dude now View Post
I had the dealership put catless primary down pipes yesterday on my M5 Competition. Next morning I had check engine light on. Took it back next day to BMW dealership. Mechanic said to get rid of the check engine light i needed a stage 2 tune. He recommended tune from DME. My question is, what if I do not want a tune? Check engine light a bad thing? Any harm to the engine, performance or anything? DME tune is $2400 stage two. That is steep. Any suggestions?
you need a tune to hide it
not accurate at all
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