Going CSL Airbox, What Are My Options?

If you’re running a CSL airbox or planning to, you’ll need to figure out what you want to do on the ECU or tuning side of things first. There are 2 main options: Alpha-N or MAP sensor.


  • No need for MAP sensor nor modified fuel rail to accept the sensor
  • May benefit (over MAP sensor route) with proper custom tune

  • ECU cannot factor variable conditions
  • Engine will run sluggish if actual oxygen flow differs from Alpha N values
  • Custom tune can get very expensive

MAP Sensor

  • Closer to OEM configuration and driveability
  • ECU has the ability to utilize an additional sensor to calculate engine flow
  • Ability to run OEM CSL MSS54HP ECU; no "tune" necessary

  • Requires purchase of MAP sensor and compatible air rail solution
  • Requires additional wiring of MAP sensor to ECU

What Did I Choose?

I chose to go the MAP sensor route. Why? Simply because I live in an area where conditions vary drastically and I want the added benefits of a MAP sensor so my engine/ECU can calculate variable flow when it needs to. In addition, I was able to save a little money by scavenging the forums and marketplace for a MSS54HP ECU with a CSL tune already on it. If you look on eBay I’m sure you’ll find a new plug and play ready ECUs for sale.

Special shout out to ECUWORX for providing diagrams on wiring up the MAP sensor and IAT to the ECU. I used this article as a resource and just providing a secondary article with picture references.

So here we go. I need to actually wire up the MAP sensor and IAT. I bought the MAP sensor conversion kit from Kassel Performance because they provide a cost-effective solution to install the MAP sensor by utilizing an existing air rail tube. No need to source an additional air rail or modify. Keep in mind this DIY is referencing the Kassel kit!

MAP & IAT Sensor Installation

1. Accessing ECU and Removal

1.1 Under the hood, reach over to the driver side corner and look for the black cover.

1.2 Use a 5mm hex to remove the screws on the box cover. There should be 4 screws.

1.3 Once you have access, you should see your ECU. It has a total of 5 plugs.

1.4 Start by removing the plug furthest from the windshield. You’ll need this clearance when removing some of the plugs.

1.5 Once all 5 harnesses are disconnected, you can slide out the ECU by pressing on the 2 small clips holding it down in the tray.

1.6 Verify you have an MSS54HP or a modified MSS54 non-HP ECU for the installation.

2. Wiring the MAP Sensor

2.1 Locate the 52-pin connector (X60003). This is the largest connect found towards the middle of the 5 plugs. You can also refer to the diagram on ECUWORX.

2.2 Use a small pick to pry up the black tab on the black harness body and release the grey connector slot. It should slide out pretty easily.

2.3 Once the grey connector is out, inspect the following pins: 16, 18. There are small numbers carved out on the grey connector. Then use the following instructions to wire the Kassel MAP sensor wiring harness.

Brown/Orange wire into Pin 16 (Ground)
Yellow wire into Pin 18 (Signal)

Keep in mind of the pin orientation. It only goes in one way.

2.4 Now locate pin 7 on the grey connector. There is an existing Red/Green wire which you will need to tap into using the supplied T-Tap connector.

Red/Green wire into Pin 7 (5V)

I used an extra heat shrink to cover up the exposed T-Tap.

3. Wire IAT Sensor

3.1 Locate pins 22 and 25 on the same 52-pin harness (X60003)

IAT wire to Yellow/Blue wire Pin 22 (Power)
IAT wire to Brown wire Pin 25 (Ground)

IAT wires do not have specific polarity.

4. Reinstall New ECU Plugs

4.1 Slide the grey connector back into the black harness and make sure it locks

4.2 Reinstall everything back together!

DIY to Wire MAP and IAT Sensor for MSS54HP CSL ECU
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