MAP DCCD VSS Install

Hi all,

I have a 92 Subaru SVX and installed a 2017 Subaru sti transmission. Due to newer models using ABS sensors to calibrate speed I needed to purchase the MAP DCCD VSS module for my speedometer to work.

I am a complete novice when it comes to wiring and hence why I purchased the EFI fundamentals and Practical Wiring courses, although neither of these courses are targeted at what I am working on at the moment they both provide excellent background and understanding.

PROBLEM - After wiring speed is intermittent and when does operate the speedometer reads signifcantly lower than actual speed compared to cell phone GPS/Speed App (15mph vs. 60 mph).

The MAP DCCD Module requires splicing into existing wires. I use T Tap Wire connectors to facilitate this. Could it be that the T-Tap connections aren't secure or not connected correctly?

The splicing module references use of open barrel slices to join multiple wires into one.

Question - would splicing each ABS wire into the correct corresponding MAP DCCD VSS Wire (ABS Sensor signal for LF, RF, LR, RR) affect with the operation of the ABS system and provide the VSS module the pulse signal it requires? Rather than T-Tap as attached pic describes, I would instead cut the ABS wire (LF for example) and join the now three wires (ABS and VSS Module Wire) via an open barrel splice.

Any advice or recommendations would be greatly appreciated.

Thanks in advance

Cjros

Christopher,

I've never used that brand VSS unit, but the instructions state:

"The MapDCCD wheel speed signal processor module has two buttons for adjusting the VSS speed higher or lower. We recommend having a passenger monitor GPS speed and adjust the VSS speed using the buttons until your dash speedometer matches the GPS speed."

If the signal is erratic, then yes I would confirm the quality of the connections. T taps are not particularly reliable, so splices would be more reliable.

That said, jumping into ABS wires may interfere with ABS operation, so I suggest testing and proceeding with caution.