Computerized vehicle failure diagnostics

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Introduction

Jimnys, as most other vehicles built in the 21st century, have several computers which control or monitor various vehicle's systems (like the engine and engine peripherals, ABS, 4WD, instrument panel, etc.).

As the 3rd generation Jimnys have been in production for 20 years (1998 - ongoing in 2018), Suzuki used a few different computers as well as communication protocols and interfaces throughout the years.

Whenever a "sophisticated" issue with the vehicle occurs, using computerized diagnostics to determine the failure code is usually essential to determine the what is actually the problem.

General info on computer diagnostics protocols

Read this article on general Wikipedia to educate yourself about various computer diagnostics protocols used in the automotive industry.

• If you are too lazy to educate yourself, you should at least know that there are two main public and manufacturer independent communication standards for vehicle on-board diagnostics - OBD1 and OBD2.
• OBD1 was used in the 1990s and early 2000s, while OBD2 (slowly) became used in the early to mid 2000s, and is still used today as the predominant public communication standard for computerized vehicle failure diagnostics.

• In Europe legislation required the presence of EOBD ("European OBD") communication interface (mostly compatible with OBD2) from 2001 for all new petrol engined passenger vehicles and from 2004 for all diesel engined passenger vehicles.
  • Japan adopted EOBD in 2004, Australia adopted EOBD in 2006 and India should have adopted it in 2013 (needs verification).
• Before those dates, European market (and probably other markets too) did not have any legal requirements regarding computerized vehicle failure diagnostics.
  • Therefore, the situation in these markets in that era varied from one manufacturer to another.
    • Some manufacturers used OBD1, some used OBD2, others used proprietary protocols, or even no vehicle computers at all.

• Bear in mind that any vehicle manufacturer still has the right to have its own (proprietary) communication protocol in its vehicle's ECU (Electronic Control Unit) in addition to the mandated EOBD/OBD2.
• The EOBD/OBD2 protocol is quite advanced and is technically sufficient to satisfy any vehicle manufacturer's needs to implement detailed and precise control and monitoring computerized mechanisms for their vehicles.
  • However, possibly due to certain lobbying efforts from the industry, the markets' legal requirements for usage of EOBD/OBD2 usually specify only a "crucial" / "basic" / "coarse" subset of all EOBD/OBD2 parameters and functions.
    • It is left for the automotive manufacturers to choose if they want to be nice / fair / friendly / open hearted and implement the remaining diagnostics functions through EOBD/OBD2, or to be stingy / unfair / conservative / assholes and implement the remaining functions and/or detailed parameters through their proprietary communication protocols (which then require the use of their special super expensive scan tools).

Diagnostics communication protocols in Jimnys

Overview

• Unfortunately, Suzuki chose to be the latter type of manufacturer (read above).
• Suzuki's ECUs (Jimnys included) always use a proprietary communication protocol, and where an OBD2 or EOBD protocol is also present (to meet certain market's legal requirements), its functionality and parameters are limited to the legal minimum.
• Before around 2001, Suzuki's proprietary protocol was called SDL (Serial Data Link).
• Since around 2001, Suzuki uses a new proprietary protocol called SDL/KWP (KWP part stands for KWP2000 technology).
• The official, and super-uber-duber expensive factory Suzuki diagnostics scan tools (the Tech1, Tech2, SDT, etc.) use one (or both) of these proprietary protocols.
  • The specifications of Suzuki's proprietary protocols of course have not been made public, but are available to aftermarket scan tool manufacturers with an annual license fee being charged.

Basic diagnostics

• The most basic / crude form of computerized diagnostic fitted to a Suzuki vehicle flashes fault codes (in a quasi "Morse code" style) on the Check Engine Light in the instrument panel when the a certain "physical" input signal (indicating "I want to see trouble codes") to the ECU is given.
  • The input signal is usually given by inserting a fuse in the 'Diag' slot in the fuse box (mainly used on earlier models) or by shorting some pins by on the communications connector.
    • This will probably be the only diagnostic method for you if you have an early Jimny (1998 - cca 2001), or unless you pay more for the factory scan tool than your Jimny is worth.
• The ECU, when invoked like this, will flag fault codes which are mainly dealing with gross errors.
  • The displayed fault codes are then cycled through showing multiple codes where they have been recorded, include some historic stored codes.

SZ Viewer program

• A very smart and philanthropic Russian programmer made a program called SZ Viewer.
  • The program is specifically designed to communicate with computers in Suzuki's vehicles which use Suzuki's proprietary SDL-KWP and SDL-CAN communication protocols.
  • The program works on Android operating system, and it is normally available from Google Play Store.
• SZ Viewer is completely free to install and use, but it really deserves some donation to the programmer.
• SZ Viewer requires the use of an ELM327 v1.4+ compatible hardware transponder (with Bluetooth or Wi-Fi communication).

• In practice, SZ Viewer can read most (and perhaps even all) Suzuki-specific diagnostic trouble codes from Suzuki vehicles' computers which otherwise require the use of original Suzuki's diagnostic tools.
  • Generic / ordinary hardware and software DTC scan tools can read only the limited/coarse "public" subset of OBD2 trouble codes which Suzuki enabled just to comply with legal requirements.

The rest of this article is to be written soon ...

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Page last edited on 21/08/2018 by user Mlines