The diagnostics port, and what’s hidden within


As drivers, most of us take the little things in our cars for granted. Decades ago we had to stand outside in the blazing heat to manually crank the engine to life before driving off. Today, all it takes is a turn of a key or the push of a button. Back in the day, you’d build biceps turning the steering wheel and today you can turn from point-to-point with a single finger. It’s certainly amazing on what modern technology can do to improve the motoring experience, although the more curious few may wonder – underneath the dashboard with all those wires, chips and circuit boards, how exactly does one understand what’s going on?

DSC_0766Wires, fuses, relays and more wires, everywhere. But beneath all the mess lies a certain system that we drivers can make use of. The Myvi’s engine ECU lies to the left of the firewall, behind the glovebox.

I’ve asked myself that very same question before, with my own car. It’s a 2011 Myvi 1.5 SE in Ivory White and while it has been relatively trouble-free from a mechanical standpoint, my curiousity was piqued when I came across an anomaly with the EPS (electronic power steering), a new feature for the model. One lengthy email to Perodua later (describing the issue and the steps to replicate it) and they escalated my case to their technical division in Rawang. They isolated the issue to the ECU on the EPS system, and Perodua’s technical engineers used a diagnostic tool which was hooked up to the car to read error codes and monitor sensors in search of the problem. Although it was not resolved that day, I left the service centre intrigued; could anything else be done with that tool?

A quick online search led me to OBD2 (shorthand for On-Board Diagnostics), an SAE standard for vehicle manufacturers to conform when building diagnostic systems for their vehicles. Predating OBD2 was OBD1 which its implementation was more of a guideline; OBD2 implementation in cars finally took off when the US mandated OBD2 on all vehicles to be sold in the country itself after 1996. The initial use of OBD2 was to monitor emissions output, but today the purpose has far expanded to other aspects including running diagnostics and rewriting ECU firmware, just to name a few.

DSC_0735An OBD2 China clone. These ones are found abundant, cheap and serves its purpose for the average technician. This particular unit comes with a power button so it doesn’t drain the car battery when it’s unused.

Generic OBD2 tools are easily available for purchase, and physically installing it to your car is a simple plug-and-play affair. Initial versions of the tool had an OBD2 female connector and a serial port or USB cable at both ends, but most tools now in the market based on the ELM327 chip have a wireless version in the form of Bluetooth or WiFi, enabling you to seamlessly connect to any Bluetooth or WiFi enabled device (i.e. your phone) easily and at a small price.

What can you do with an OBD2 diagnostic tool? When an ECU detects an issue, it logs down the error in the form of an error code along with ‘freeze frame’ data, which the technician may utilize to effectively pinpoint the malfunctioning component without going through the time-consuming process of evaluating symptoms and eliminating factors. Once repairs are completed, the technician then uses the tool to remove the logged error.

Naturally, there will always be the adventurous few who do not want to bring their cars in to service centers or workshop just yet, preferring to first get a grasp of the issue before sending it in. The last thing you want would be to come up with a throttle body gasket leak, and end up replacing everything except said gasket. However, with the OBD2 tool in hand and with some basic knowledge, you can easily pin-point the root cause for error codes, along with the necessary parts and repairs – potentially saving you effort, time and money. In fact, last I heard – a single scan at a Perodua service center can set you back at least RM50!

DSC_0779Once the tool is connected, depending on the app – you can monitor engine sensors, clear error codes and much more all from your phone itself.

Now before you run out to buy your own tool to experiment, it’s not a given that the tool will work straight out the box, with your car. Most Perodua owners may already be aware of this since, given that 99% of all generic tools out there will not connect with their cars. I hated this fact and sought out to find out why. After all, if the tools in the service center could work, there’s no reason why the generic ones shouldn’t.

DSC_0740Most of the tools out there communicate wirelessly without interference so you can mount your phone (or tablet if you prefer) to a location of your liking.

The initial question I asked myself all those months back has now grown to be a personal project of mine – with considerable success. What was initially thought to be available only to authorized service center technicians, is now available to every driver. It’s also more than just a tool to assist repairs – track enthusiasts can use it to monitor essentials like coolant temperatures, AFR and knock without physical gauges when pushing their cars to the limit, hypermilers can accurately monitor their fuel consumption figures, and daily drivers can use it to monitor their car battery to get an idea on when it is due for replacement.

In my next article, we take a deeper look on how the OBD2 works and which sensors can be monitored on the 2011 Perodua Myvi. Stay tuned!


About Author

Having a penchant for cars since youth, he firmly believes that speed and stature go hand-in-hand. He enjoys the occasional spirited drive and can be found personally grooming his cars from time to time.


  1. chin ping shoon on

    hii… great to find this article, am having trouble reading the fuse&relay box diagram perodua myvi… do you happen to have the exact name to those short-form shown at the fuse box… tq

  2. Hi, do you happen to know where is the grounding / earthing point in the Myvi Glove Box ? Appreciate if you could advice

    • Sorry Chong – would love to answer your question but I’m not too sure myself, but typically any unpainted area connected to a main structure on the chassis could work as a ground.

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