[335MRod]

I own a 2011 335i with Harness A

A friend of mine is selling me his JB4, which is basically new. and I'm getting a really good deal. His JB4 is Harness B. Now my question is the following:

Currently, I have an N20 3.5 TMAP which uses Harness B plug, meaning I will need an adaptor to connect it to the TPMA plug. ( I already own the adaptor, which I use to connect to my N20 TMAP sensor).

Now, if I swap out my MAP sensor for one that uses a harness B plug, could this work? Also, using another adaptor to connect JB4 and MAP harness ( already have an extra one)..

It works... switched out MAP sensor to type “B” and hooked everything up. Works great, no issues..

[weehe126]

If you have a N20 TMAP sensor a type B JB4 should plug right in.

[335MRod]

Originally Posted by weehe126

If you have a N20 TMAP sensor a type B JB4 should plug right in.

Yes, the B harness works for the TMAP since I have the N20 sensor. But the MAP sensor on the intake manifold is type A. I think of switching it out to a type B and then using the other adaptor that I have..

[Turbod]

Keep in mind that you also need to plug the factory wiring harness into the JB4. So even if you replaced the MAP sensor you will have type A plugs on your engine harness that will need to be connected to the type B JB4 harness.

[335MRod]

Originally Posted by Turbod

Keep in mind that you also need to plug the factory wiring harness into the JB4. So even if you replaced the MAP sensor you will have type A plugs on your engine harness that will need to be connected to the type B JB4 harness.

Looked and compared the plugs and wires that connect to ECU box, the only difference was the TMAP & MAP. What am I missing?

[Turbod]

Originally Posted by 335MRod

Looked and compared the plugs and wires that connect to ECU box, the only difference was the TMAP & MAP. What am I missing?

The TMAP and MAP are the only differences in the JB4 harness. When you hook the JB4 up to the car you need to plug the JB4 harness into the car's sensors as well as the vehicles factory wiring harness. You said you would use the 3.5 bar TMAP sensor which solves one of four connections. If you swapped the MAP sensor to the B type connection you are still left with the factory engine harness having two type A connections that need to also plug into the JB4 harness.

Maybe you already realize this? Just wanted to keep you from spending money and running into headaches during installation.

[carguy138]

Originally Posted by 335MRod

I own a 2011 335i with Harness A

A friend of mine is selling me his JB4, which is basically new. and I'm getting a really good deal. His JB4 is Harness B. Now my question is the following:

Currently, I have an N20 3.5 TMAP which uses Harness B plug, meaning I will need an adaptor to connect it to the TPMA plug. ( I already own the adaptor, which I use to connect to my N20 TMAP sensor).

Now, if I swap out my MAP sensor for one that uses a harness B plug, could this work? Also, using another adaptor to connect JB4 and MAP harness ( already have an extra one)..

FYI I'm selling a N55 JB4, harness A. It's in the classified section and works great. I got sick of taking it off for inspection so giving MHD stage 1 a shot.

[335MRod]

Originally Posted by Turbod

The TMAP and MAP are the only differences in the JB4 harness. When you hook the JB4 up to the car you need to plug the JB4 harness into the car's sensors as well as the vehicles factory wiring harness. You said you would use the 3.5 bar TMAP sensor which solves one of four connections. If you swapped the MAP sensor to the B type connection you are still left with the factory engine harness having two type A connections that need to also plug into the JB4 harness.

Maybe you already realize this? Just wanted to keep you from spending money and running into headaches during installation.

The only two other plugs left are the boost solenoid, and the one to the fuel rail which plugs are the same. The wires to the ECU are also the same, I already verified this..

[335MRod]

Just installed, and it works fine. Replaced MAP with type “B” and plugged everything else in. Works great, no issues.

[Turbod]

Originally Posted by 335MRod

The only two other plugs left are the boost solenoid, and the one to the fuel rail which plugs are the same. The wires to the ECU are also the same, I already verified this..

What I was saying is this. The JB4 plugs into the sensors on the engine and then also plug into the factory wiring harness. If you had Type A plugs on the sensor originally then you would have Type A plugs on your factory wiring harness. By changing the sensor the JB4 would plug into the sensor without any issue but would be incompatible with the factory wiring harness. Remember that the JB4 piggyback takes the signal, changes it, and sends altered data back to the DME. For every sensor connection you have two plugs on the JB4 wiring harness, one for the sensors, one for the factory wiring harness.

If you got it to work then great. Not really sure how it worked but I'm also not invested enough to care, lol.

[335MRod]

Originally Posted by Turbod

What I was saying is this. The JB4 plugs into the sensors on the engine and then also plug into the factory wiring harness. If you had Type A plugs on the sensor originally then you would have Type A plugs on your factory wiring harness. By changing the sensor the JB4 would plug into the sensor without any issue but would be incompatible with the factory wiring harness. Remember that the JB4 piggyback takes the signal, changes it, and sends altered data back to the DME. For every sensor connection you have two plugs on the JB4 wiring harness, one for the sensors, one for the factory wiring harness.

If you got it to work then great. Not really sure how it worked but I'm also not invested enough to care, lol.

For the factory harness I used BMS A->B adaptor.. pretty easy.