A brief description of the Suzuki Serial Data Link (Suzuki SDL)

The Serial Data Link is a diagnostic interface that allows fault codes and real time data to read from the ECU. This interface is very rarely referred to in documentation for early models but is sometimes shown on the schematic. There are two different connectors used, a 12-pin ALDL style connector and a 16-pin J1962 (OBD2) connector.

ALDL Connector

The ALDL connector is common on early models and has the SDL on pin M, Pins H and A provide 12V power and ground for a scan tool.

OBD2 (J1962) connector

The J1962 connector has the SDL on pin 9, this pin is reserved by the OBD2 specification for the manufacturers own use. Power for a scan tool is provided with 12V on pin 16 and ground on pin 5.



The SDL is bi-directional one wire interface, there are few hand held scan tools available and these are intended for dealer use and cost thousands of dollars new. Vetronix (now Bosch) made the original Suzuki dealer tools, the Tech1 and the Tech 1A. Tech 1/1A cartridges can also be used in the Vetronix/Bosch Mastertech MTS3100 tool which also has a lot of extra functionality. The Tech 1A was replaced as the dealer tool by the Tech2, Suzuki cartridges for these are available through eBay but are most likely to be cloned, a prospective purchaser would need to check which models are supported. There was also a Carman tool available but information on this is limited. The latest dealer tool is the SDT, as far as I know this tool has no support for Suzuki SDL. To make the Serial Data Link available at an affordable cost I have produced a USB-SDL interface that can be used with a PC or laptop, please go to the RhinoPower Forum for details. Interfaces designed for GM vehicles have been used with some success but the voltage levels are different and none are guaranteed to work.
The communications protocol is the same for all models but there are differences in baud rate, address locations and scaling factors.

The SDL uses binary data, there are four defined fields as shown in the table below.

The header byte is made up of an ECU type and a message type, ie 1Xh is an engine controller message, 2Xh is an ABS controller message. X3h is a data request and X0h is an ID request.
The length byte is the total length of the message including header and checksum. The number of data addresses that can be requested is ECU specific, up to eight data bytes can be requested at a time.

    Send To ECU:

    Header = $13
    Message length = $04
    Address = $00 to unknown (will depend on ECU)
    Checksum = all bytes sum to zero

  ECU returns:

    Header = $13
    Messsage Length = $04
    Data = ?
    Csum

The Address Look Up Table

The address is defined by a look up table in the ECU. The table below shows the addressing for a G13BB engined Jimny with a 1903 ECU ID. The first column is the OBD address, the second column is the actual memory address that is read.

0     390h     Fault Codes 1
1     391h     Fault Codes 2
2     392h     Fault Codes 3
3     393h     Fault Codes 4
4     0h     RPMH (RPM*5)
5     1h     RPML
6     396h     Target Idle
7     52h     VSS
8     397h     CTS
9     398h     IAT
10     399h     TPS Angle
11     2Ah     TPS Volts
12     39Ah     O2 Sensor
13     39Dh     InjPWH
14     39Eh     InjPWL
15     39Bh
16     39Ch     MAP Sensor
17     38h
18     100h     Status flags1
19     78h     Long Term Fuel Trim
20     7Bh     Short Term Fuel Trim
21     39Fh     Current Fuel Trim
22     46h     Batt Volts
23     12Dh     Ignition Timing
24     3A0h     EGR Opening
25     3BAh     Status Flags2
26     3B9h     Status Flags3
27     3A1h     Timing Adjust
28     3B0h

So to read the TPS voltage send:
    $13, $04, $0B, $DE
The ECU will respond with:
    $13, $04, Position, Csum