Coding Plug

[Three Dee]

I just picked up a nice Motometer instrument cluster for my '86 eta, which will soon have an '89 325i engine under the hood. The reason I bought the "new" cluster is, of course, because I need the 7000 rpm tach. The odometer gears need replacing of course (I have the covered already), but the SI board looks brand new, with absolutely no sign of any corrosion. It looks like the manufacturing date is 0187. However, the coding plug is missing.

What, exactly, does the coding plug do? I can't figure out if the coding plug should be specific to the engine, the OBC or what.

[AndrewBird]

The coding plug tells the tach what engine is in the car so it will read correctly. All you need is a 6-cylinder coding plug, so your old one will work fine.

[reelizmpro]

Hmmm I don't know if the tach will be accurate with the ETA chip if he has a 325i engine. I have a 325i coded chip if you need it. 325i engine, 325i cluster...just makes sense to have the correct chip anyway.

[AndrewBird]

99% sure it doesn't matter. Just needs to be a coding plug for a 6-cylinder car.

[reelizmpro]

Then y do the m50/s38 swap guys run e28 m5 coding plugs? Not all 6 cylinders are the same.

[James Crivellone]

Then y do the m50 swap guys run m5 6 cylinder plugs? Not all 6 cylinders are the same.

The M5 plug (from an E28 M5) only calibrates the tach for a 6 cylinder engine with an 8000RPM Tach.

Any 6 cylinder coding plug from an M20/M30, etc will work with any M50 with a 7000RPM Tach.

The ETA tach coding plug just calibrates the gauge for a 5000 RPM Tach, SuperETA 6000RPM Tach, etc

[reelizmpro]

Exactly my point. Eta plug for 5k rpm tach. I plug for 7k

[Three Dee]

The coding plug tells the tach what engine is in the car so it will read correctly. All you need is a 6-cylinder coding plug, so your old one will work fine.

My eta has the black plastic plug that goes in from the back, so I know that won't work. This cluster should have the white plug that plugs in at the bottom of the tach side of the gauge, behind the trim panel.

reelizmpro, what are you asking for that plug?

[Three Dee]

99% sure it doesn't matter. Just needs to be a coding plug for a 6-cylinder car.

This is completely off subject: I like that pic of the '70 MGB GT. I had a '69 model that turned out to be a rust bucket, so I had to scrap it, but it was fun to drive while it was drivable! I still have a mess of parts left over from it.

[GrigorPetrov]

To sum up the information!!! if you change m40 with m50/52 to have a speed signal and economiser you should change the plug only not and the whole cluster with the plug, right ??? the plug have to be from 6 cylinder e30s

[AndrewBird]

Exactly my point. Eta plug for 5k rpm tach. I plug for 7k

Duh, I didn't think about them having different redlines.