Telematics Control Unit (TCU)

Introduction

The Telematics Control Unit (TCU) provides connectivity to the Nissan Leaf. It is a 2G, 3G, 4G or 5G modem, depending on the year and region, with additional functionality. The TCU provides internet connectivity to the AV Control Unit via USB, while also communicating with Nissan's servers in its own right to provide CarWings / Nissan Connect functionality such as remote climate control.

4G TCU from a 2019 Nissan Leaf, attached to its mounting bracket

Location and access

The TCU is located on the right-hand side of the vehicle in all models.

Left-hand drive

The TCU is located behind the glove box. Access is achieved by removing the glove box.

Right-hand drive

The TCU is located above the pedals.

Variants

2G

Part numbers:

• 283B0 3NM0A

4G

Part numbers:

• 28275 5SA0B

These are found on some 2nd-generation Nissan Leafs. It includes a Sierra Wireless AirPrime AR7554 modem module, a chip labelled R7F7010259 (possibly part of the Renesas RH850/F1L family) and a small PIC16LF1518 chip.

It does not contain a physical SIM slot.

• 
  External view
• 
  Circuit board side A
• 
  Circuit board side B

Connections

Connector Number	Physical Description	Diagram	Purpose
M67	TH40FB-NH (40-pin connector)	File:ZE1 M67 Connector.png	Power, Microphone, CANBUS (IT-CAN and M-CAN)
M173	USCAR30-MD-M (USB)		USB connection to AV Control Unit
M174	FAKRA CODE H 4003 (Pink)		GSM antenna
M175	3FA1ANCSJ-C02W0 (Blue)		GPS antenna

M67 Pinout

Terminal No.	Color of Wire	Signal Name
1	W	+VBAT
2	R	ACC
3	BR	ACC OUT
5	LA/L	LED GREEN
6	SB	CAN-H
7	V	CAN-L
8	–	–
9	–	–
10	G	WAKE UP/IGN
11	SHIELD	MIC OUT GND
12	L	MIC OUT SIGNAL
13	–	–
14	–	–
15	–	–
16	SHIELD	MIC GND
17	L	MIC SIGNAL
18	P	MIC VCC
19	–	–
20	–	–
21	–	–
22	–	–
23	–	–
24	–	–
25	–	–
26	SB	M CAN-H
27	LG	M CAN-L
28	B	GND
29	B	GND
30	–	–
31	G	AUDIO HU OUT+
32	R	AUDIO HU OUT–
33	–	–
34	–	–
35	–	–
36	–	–
37	LA/Y	ECALL SW
38	–	–
39	–	–

5G

Part numbers:

• 28275 6HL9B

• 
  External view
• 
  Circuit board side A
• 
  Circuit board side B

Open-source Telematics

Owners who cannot use Nissan Connect (e.g. because it is not offered in their country), or don't want to use it, have a couple of options.

OVMS is an open-source module that can provide all sorts of telematics functionality such as GPS positioning, remote climate control, remote lock/unlock, battery monitoring, etc. In Gen 1 Leafs it can be installed via a simple plug into the OBDII port. In Gen 2 Leafs, a custom adaptor cable can be made to tap into the power and CAN buses at the CAN Gateway. It is also necessary to disable the TCU, either by disconnecting the CAN BUS wires on its connector, or by removing it completely and replacing it with a couple of bridging wires and a 5V regulator to keep the AV Control Unit powered, power the microphone and pass its signal through.

For 2G TCUs, it is possible to replace the SIM and configure the TCU to connect to a server of one's choosing.

External Links

• Reverse engineering Telematics Unit - My Nissan Leaf Forum
• (2018+) TCU Decoding and Emulating - My Nissan Leaf Forum
• https://github.com/developerfromjokela/nissan-leaf-tcu
• DEF CON 25 - Mickey Shkatov, Jesse Michael, Oleksandr Bazhaniuk - Driving down the rabbit hole - YouTube