ALDL Cables VS OBD2 Cables
Why is it important to understand the difference? Cant I just use any old cable?
Well, the Simple answer is no. No-one likes to be ripped off or buy the wrong cable, or simple buy something that just doesnt work, so its important to understand what your buying or using to make sure its going to actually work!
Holden Commodores use two different diagnostic cables to diagnose faults and communicate with the car ecu. There are alot of names and terms thrown around including ALDL, OBD2, ELM, VPW, CAN, GM OBD1 and a whole lot more. But, these names done mean all the same thing!
Alot of these terms are used interchangeably on forums and sites causing alot of confusing but in reality they all correspond to a different cable type and commnunication protocol.
So whats that mean in the commodore world? Well, it means that only certain cables and protocols can be used to communicate to your cars ecu,instrument cluster, Body control module or even the radio.
What is the main difference between an ALDL cable and an OBD2 Cable?
Both cables are used for diagnostic purposes, but each “speak” a different language (known as a protocol). Therefore using the wrong cable in a car that doesnt support that “language” means it will not be able to understand and communicate to the cars modules.
In terms of Holden Commodores: VR,VS,VT,VX,VY and VZ Holden Commodores all use the ALDL protocol to communicate with the major car components. Although all LS1 V8’s require an OBD2 Cable to view engine data.
Below is a summarized table of the supported protocols for each Holden Commodore:
- VR Commodore – ALDL
- VS Commodore – ALDL
- VT Commodore – ALDL, OBD2 – V8’s only – VPW
- VX Commodore – ALDL, OBD2 – V8’s only – VPW
- VY Commodore – ALDL, OBD2 – V8’s only – VPW
- VZ Commodore – ALDL, OBD2 – CAN 11bit
- VE Commodore – OBD2 (CAN 11bit, CAN 29bit)
1.0 What Exactly is an ALDL Cable? Whats is it for?
Starting with ALDL cables (Also know as OBD1 or GM OBD), these types of cables communicate over a very basic protocol. This protocol is”non standardized” meaning GM implemented a communication protocol that is not be exactly the same as any other vehicle let alone any other manufactures.
Specifically looking at Holden Commodores, VR to VZ Commodores use this Protocol to communicate been majority of the cars electronics to pass important information and status’s ranging from seat-belt status all the way to airbag deployment.
This information is sent out in an orderly fashion that all the cars electronics can see, It is mainly directed at the BCM (Body Control Module) since it is the BUS master which looks for all the other modules signals to ensure all components are working correctly.
Enough about the modules, looking more into the inner workings of an ALDL Cable, the information obtained from the car is fed directly through the ALDL cables chip and the raw data is passed onto the computer.
So why is this important? Imagine 20 people all trying to speak at once, it would feel pretty crowded and “noisey” wouldnt it? Meaning that alot of information is being passed all time so any software developed for ALDL cables needs to be efficient and effective to be able to keep up the the busy line!
This is also why it is so important to have a high quality ALDL cable to ensure no bad data or corrupt data is picked up!
All VR,VS,VT,VX,VY and VZ Holden Commodores use ALDL for the majority of there electronics, this includes the instrument cluster,abs,bcm,radio,TC and engine data (Only for V6). A key note there is that engine data (PCM) can only be read on V6 commodores, whereas the V8 commodores will use OBD2 protocols for engine data.
1.1 What are the main uses of an ALDL Cable?
ALDL Cables can be used for many different purposes, these can range from scanning for engine diagnostic codes using pre-existing software to reverse engineering the cars communication and messages.
Majority of use will be for the first option, scanning for diagnostic trouble codes which can be done using Ultimate Commodore Customiser or engine related codes only by tuner pro
And for advanced users, available free tuning software packages such as tunerpro and OSE tool can be used to download the current PCM/ECU calibration and tune their V6 Holden Commodores, although this is only available for certain vehicles!
1.2 What software is available for an ALDL cable?
Some of the recommended softwares to be used with ALDL cables on Holden Commodores include:
- Ultimate Commodore Customiser
- EfiLive V4
- OSE Tool (Advanced Users Only)
As with any software, great deal in care and research needs to be done to ensure that the software is suitable for your car so that it does not change or harm anything in your car!. The above mentioned ALDL software are tested softwares for use with our recommended ALDL cables and are great tools for diagnosing,testing and learning about your Holden Commodore!
2.0 What Exactly is an OBD2 Cable? What is is for?
Now how does an OBD2 Cable differ?
Obd2 is the “Generic” name for this communication language. But in fact, theres a whole heap of OBD2 lanaguages, think of it as being able to speak English with a different accent, it sounds similar but isnt quite the same.
OBD2 has a major difference in the interpreting of this data compared to ALDL, its all standardized therefore it is very simple to understand. All models and manufactures must meet the bare minimum criteria which includes looking up fault data, engine data and other diagnostic information.
This means theres a whole heap of available information,software and knowledge on the web as this standardized protocol is widely used,reversed and developed around the world. Looking specifically at the commodores, the OBD2 protocols that GM uses is VPW and CAN protocols. So technically, ALDL, VPW and CAN are all different protocols, that speak different languages and all have there specific functions.
OBD2 Cables main use is for looking up diagnostic trouble codes,history fault information and also viewing live engine data. The most common scantool for this job is the ELM327 cable as pictured to the right. It is cable of communicating over all of these OBD2 protocols, and using one of the many diagnostic softwares available allows the backyard mechanic grab diagnose any engine related problems.
2.1 What are the main uses of an OBD2 Cable?
As previous discussed, the main uses for an OBD2 cable is for diagnostic purposes and for live engine data viewing. Other uses can be to reverse engineer your cars communications, cool little hacks/changes such as displaying custom text on the radio screen or Instrument cluster screen can easily be performed though a bit of listening and tinkering!
Advanced functions of OBD2 cables can be to perform programming changes to different modules including coding keys, editing instrument cluster settings, tuning ECU ect. The possibilities are endless when using a nifty cable such as the ELM327, these diagnostic cables are capable of perfroming all the major tasks that can be done by the multi-thousand dollar scantools, all thats need is the right software.
2.2 What Software is available for an OBD2 Cable?
There are so many OBD2/ELM327 Softwares available on the market, that its really a matter of picking which one has the greatest support list! Unfortunately there is no “Holden Specific” software available for OB2 cables, but most software will be able to view generic fault codes and error as well as show basic engine data including engine speed, 02 senors, MAF ect.
It is recommended to use software that states “GM” supported, Holden is apart of General Motors therefore most of the content will overlap will Holdens and will provide better manufacture specific information about the cars engine specifics and fault errors.