I have been looking over the Wire diagrams for the Tire pressure Control Unit (TPCU). (also called the RDK) Pin 1 of the TPCU goes to Pin 10 of plug 2 (Radio TX) and Pin 2 goes to pin 11 of plug 2 (Radio RX).

Q: Why is the TPCU connected to the TX and RX of the Radio?
A: There is no transmit function on the radio. Error in the wiring diagram?

Pin 20 of the TPCU going to Pin 4 Diagnosis K, Pin 1 of the EZK and Pin 12 of the LH.

1. What is Diagnosis K?
2. Why does the TPCU communicate with the EZK and LH?
Pin 19 of the TPCU going to Pin 6 Diagnosis L, Pin 7 of the EZK and Pin 16 of the LH.

1. What is Diagnosis L?
2. Now we have a pair of wires going the the EZK and LH, what do they do?

Diagnosis-L is identified on the EZK Test Plan as "Diagnosis Inciting Lead (L-lead)"
Diagnosis-K is identified on the LH Test Plans only as "Diagnosis (K-lead) from diag. conn. 10"

I suspect that this means that the Tire Pressure Control Unit is not communicating with the EZK and LH units, but that all three are hooked to common diagnostic connector pins.


Being that Pins 8, 26, 28, 29 of the TPCU is going to the ABS / PSD Control Unit and Pins 19 and 20 going to the EZK and LH tells me the TPCU is not just there to monitor the air pressure, but to assist in traction control.

Nope - No traction control, I'm afraid.

Wally Plumley
928 Specialists


RDK sensor

Pictures of a RDK sensor 928 606 414 00