ZF 8HP — Wiring

This page describes how to connect a BMW / ZF 8HP transmission and its shifter to IOcan. Before wiring, familiarize yourself with the general Wiring Concepts and the device pinout.

Overview

The 8HP communicates on two CAN networks, PT_CAN and PT_CAN2. Both are transmission-side networks and are typically connected to CAN1 and CAN2 on IOcan (the assignment is configurable):

8HP signal IOcan connection
PT_CANH / PT_CANL CAN1H / CAN1L
PT_CAN2H / PT_CAN2L CAN2H / CAN2L
Wakeup PWR6/WAKEUP OUT
KL30B KL30B OUT
KL31 battery − / chassis ground

IOcan supplies both power (KL30B) and the wake-up signal to the transmission — no external relays are required.

Transmission connector

Pin Function
3 PT_CAN2L
4 PT_CAN2H
5 PT_CANH
6 PT_CANL
9 Wakeup
13 KL30B
14 KL31

PT_CAN / PT_CAN2

Two CAN bus networks responsible for all communication with the transmission. Both networks are not terminated at the transmission and require 120 Ω termination. IOcan provides configuration-switchable 120 Ω termination on each of its CAN interfaces.

Both networks have to be connected to IOcan and to the shifter (if a BMW 8HP F-series shifter is used).

Wakeup

This terminal has to be connected to the WAKEUP OUT pin on IOcan.

KL30B

This terminal has to be connected to KL30B OUT on IOcan. This is a current-carrying connection which has to be made with wire of 2.5mm².

KL31

This terminal is ground for the transmission. This is a current-carrying connection which has to be made with wire of 2.5mm².

Shifter

With an OEM BMW F-series gear selector (GWS), the shifter is wired to the transmission-side networks so it communicates directly with the TCU:

  • Wire the shifter to both PT_CAN and PT_CAN2.
  • PT_CAN is not terminated inside the shifter — terminate it at the shifter end with a 120 Ω resistor.
  • PT_CAN2 is internally terminated with 120 Ω inside the shifter.

Full connector details, part numbers, and cross-compatibility variants (for example an 8HP shifter with a DCT transmission, which requires protocol translation through IOcan) are documented in the BMW F-series GWS pinout.

Non-OEM driver inputs — paddles, sequential shifters, CAN keypads — connect to the vehicle side of IOcan instead. See Wiring Concepts for the vehicle/transmission network separation.

Power wiring summary

Connection Wire gauge
IOcan KL30 IN / KL31 at least 1.5mm²
Transmission KL30B and KL31 2.5mm²
IOcan KL15 IN 0.35mm²

Use twisted pairs for all CAN wiring, keep stubs short, and crimp all terminals properly — soldering is discouraged.