OBD1 on an OBD2 ECU aka "Suzuki Mode"

Strictly speaking this article should be called OBD2 on an OBD1 ECU as Suzuki retained an 'OBD1' serial link on all their ECUs intended to be accessed only through their, very expensive, main dealer only scan tools. An OBD2 interface is also fitted for markets where a form of OBD2 is legislated and is limited to the minimum legal requirement. This gives their dealers a huge advantage over independant garages, who can ony access OBD2 data, when it comes to diagnosing and repairing Suzukis. The main Dealer scan tools also have an OBD2 capability for working on other makes.

RhinoPower is developing a scan tool and software that will enable both OBD2 and OBD1 to be accessed on Suzuki vehicles. Please note that when I refer to the 'OBD2 spec.' I really mean the collection of umpteen different specs that make up what we generally refer to as OBD2 or EOBD.

Suzuki ECUS with OBD2 generally use one of the following Suzuki proprietary protocols:

On some US models from 1996 to 1998 an SDL interface was implemented on a different pin to the OBD2 interface. On the Esteem ECU this pin was marked 'SDL' and the oBD2 pin 'SDT'. The SDL interface added the capability to operate various ECU controls.

SDLJ1979 was used on some US models,from 1996 through to around 1998, it retained the original SDL software protocol but shared the ISO9141 hardware interface with the OBD2 capability. The interface operates as OBD1 by default but after receipt of an OBD2 init command the data is passed to the OBD2 software functions until an end of communications message is received or a comms timeout occurs. The table at the bottom of this page gives a comparison of OBD1 v OBD2 capabilities on a 1996/98 US Sidekick/Tracker ECU.

From some time around 2001 through to around 2010 Suzuki used a European diagnostic protocol called KWP2000. A variation of this protocol is also used for OBD2 but OBD2 is a very limited subset of the protocol specified by ISO14230-4.

I've yet to delve into the inner workings of the CANBus ECUs but, as I understand it, these ECUs use the same KWP2000 protocol as the KWP/SDL ECUs.

Some Suzukis that use an engine and electronics bought in from another supplier may use a protocol proprietary to the engine supplier. Some Suzuki models with FIAT diesel engines are known to use a FIAT variation of KWP2000.

* memory read/write allows any RAM address to be accesseed and also allows a test programme to be loaded into RAM that can be used to test the ECUs functionality or to read any memory address in ROM.

There are more OBD1 modes that haven't yet been reverse engineered.