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BMW 135i – BMW JB4 Install (N54)

I finally pulled the trigger on JB4 and decided to order the BMS clutch stop at the same time. Both products arrived in a few days and I installed them right away.

When I bought the car, the previous owner told me it had some sort of JB tune that was wired inline with the MAP sensor. After doing some research, I thought he was referring to JB+ which would increase boost an additional 2-5psi for an extra 20HP.

Before I could install JB4, I had to remove the JB+ chip that I thought was in the car. I removed the whole intake assembly but found no trace of the chip. I assumed the previous owner lied about it and continued on with the JB4 installation. Once I popped the ECU box open, I saw wires with electrical tape and some sort of aftermarket box with a toggle switch connected to it.

jb3

Since I was confused, I posted up a few pictures on N54tech and Terry identified it as a really old version of a pin-out JB3 tuner. The toggle switch was in the “off” position, so he advised me to carefully remove the harness and plug the wires back into the factory ECU connectors.

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