The diagnostics port: where everything comes together


In this third and final part of our writeup (Part 1 and Part 2 here), we put the technicalities aside from our last article and get down to the fun – making it all work for you. With smartphones of this era capable of replacing your point-and-shoot camera, along with making cashless payments at your grocery store, what’s a phone to do when you get into your car?

First thing to bring to the table – analog gauges are a thing of a past. Sure, there are gauges with multi-functions and segmented digital displays but in terms of customization, that’s about as far you’ll get. To some, a phone on a dashboard may seem rather out of place where as analog/digital gauges are the real deal. It’s exactly the same debate with carburetors and fuel injection systems – the latter is more precise, adaptive and customizable, and can be had for cheap.

Another benefit – there’s no permanent installation required for a sturdy and solid phone mount (if you think that’s not possible, look at RAM mounts) but on the other hand you’re going to have to pull and route wires from the engine past the firewall, along with drilling holes and mounts to install the gauges. Dangling cables and a dashboard surface filled with holes may pass for cars built for to win on Sunday, sell on Monday but when you’re going to own it for several years you don’t really want to stare at a dash which looks like a block of Swiss cheese.

defi-02I do have to admit that having those gauges on the dash expresses that ‘because race car’ feel, but don’t forget that it’s Malaysia and you’re certainly going to attract people to your car for the wrong reasons as it makes it seem you’re packing some performance (and nice parts) under the hood. Image from TegiwaImports.

One point of debate is that tuners argue on the accuracy of data coming from electronics. Some gauges from Defi or Autometer retrieve their readings directly from their own sensors installed onto your vehicle, such as oil temperatures which are typically located and measured at the oil filter via a sandwich plate. However the counter-argument here is that most sensors from factory are built for robustness and reliability as they act as the eyes and ears of the ECU – which means they are built to last and to be accurate as for the entire car’s lifespan. With everything in the engine bay almost electronically controlled you can be sure manufacturers aren’t going to skimp on sensor quality!

Below are some ideas which you can put your OBD tool to good use:


The 2014 Mazda2 came with a heads up display, or HUD which the driver could read vehicle speed along with other measures on a glass screen. It’s not something new, as a few cars from the 90s already had segment-display HUDs as an add-on option like the 240SX sold in the US. LCD screens during those times were anything but highly visible and readable – now fast forward to the 2016 and you now have phones and tablets, which their matrix screens can display anything, yet be crisp and bright enough to read under the sun.

The way it works is that the phone displays a mirrored image of the screen, which is placed on your dashboard, facing the windscreen. The windscreen reflects the mirrored contents to your view, which you now be able to see the HUD from your driver’s position. Torque Pro and DashCommand has a HUD mode which allows you to do just that. Monitoring just got much easier and faster without taking your eyes off the road.

OBD2 pt3 (3)This is how it looks from the driver’s seat. Depending on the size of your phone or tablet you may want to resize the text till it’s large enough for you to view but also not obstruct your vision of the road. If you feel that it’s too bright and distracting you can always reduce your screen’s brightness, and you would want to place it in a location to minimize eye movement. And if you think there’s something wrong with the HUD…

OBD2 pt3 (5)… you’re probably right. The HUD has a bit of ghosting due to the reflections from the inner and outer surfaces of the windscreen. However, as the outer reflection will always be darker than the front you’ll eventually get used to it. If the double vision gets to you, you can always try placing the phone at an angle to reduce the ghosting effect.


Apart from the common usage of using your phone as a GPS, you can take it one step further to use it as a drive logger which overlays the roads taken with a colored heatmap which is tied to a PID value. Want to measure how fast you were going at the entry and exit points of a corner, or to map out your fuel consumption  for the entire course of your journey? This feature on Torque Pro with your custom PIDs will do just that.

OBD2 pt3 (8)My recording from Puchong to KLIA2, with the heatmap representing the speed of my driving in km/h. The long highway roads meant I could drive a little faster; my justification is so that I could show you, the reader – about this interesting piece of functionality. Keep your eyes peeled on the road, and always adhere to speed limits!

OBD2 pt3 (9)A zoomed in section of the turnoff from the ELITE highway to KLIA – you can zoom in into your recording to get better readings. As this road is often deliberately slicked, always be sure to exercise caution! 


Those fond of statistics will love this one. With your custom PIDs, you can plot their values onto a line graph, with the X-axis for time. Perfect for investigating relationships of values (such as RPM and injector pulse widths, or AFR vs RPM).

OBD2 pt3 (6)With the graph, you can log any PID to test for peculiarities or to ensure your piggyback is running at its proper settings. In this image above I logged my engine RPM and my injector opening times, and gave the car a little more gas at the middle hence the big spike. Still unsure on the reason for the sudden increase in injector time even before I hit the throttle though, I should have logged the AFR along…


You’ve probably read or heard cases where cars could be remotely controlled, and in reality it’s not far away from the truth. The buttons you press on your dash isn’t exactly a switch, per se – it actually informs the body control ECU to send a command to another ECU which then activates that function. Your OBD2 tool and your phone essentially are able to replicate that same button, which turns your phone into a remote control of sorts.

It sounds complicated, yes – and a discussion on this topic can certainly warrant an article of its own. For example, car auto-locking feature, which automatically locked the doors once you drive above a certain speed limit were removed in Malaysian vehicles, for whatever reason. This feature can be replicated via commands and monitoring PID values (for example, if vehicle speed is above 30 km/h and vehicle is not locked, send command to lock). The autolock OBD2 plug-in tool found for most cars emulates this, although the said function is fixed.

autolockYou can find these tools which you plug into your OBD2 port, along with other functions. Unlike the OBD tools discussed previously this one has a fixed function and can do nothing else but automatically lock your doors when you go above a certain speed limit. Image from

A concern for most owners with wireless OBD tools would be security. Unfortunately, this is a valid fear, with most vehicle computer systems that I’ve worked on so far only implementing simple identification processes – or sometimes not at all, which is rather alarming. The OBD port was designed with the intention to be used with wired devices, requiring a technician to be in your car and which meant the car had to be unlocked. Wireless OBD tools may ease performing diagnostics but there are increased risks.

With that said, it is important that your wireless OBD tool uses a secure wireless infrastructure. Bluetooth is commonly used and requires pairing to connect to the tool. However, the downside is that most of the tools from China have common and easy-to-guess passwords which are easily compromised. WiFi has a far bigger range, which in turn makes it easier for would-be intruders, and makes it worse if it implements an already compromised security algorithm like WEP. With cases like these it’s absolutely recommended you buy OBD tools that come with a physical power switch which you can manually turn it off. Most cars do not supply power to the OBD port when the engine is off – the car we’re working on exhibits this behavior – but be sure to check on your own car. As cars are increasingly controlled by 1s and 0s than nuts and bolts, taking advantage of factory electronics will be essential to get the most out of your drive.

Have you had any interesting projects with your car and the OBD tool? We’d be happy to hear them in the comments!



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. Nice article…I will gather the hardware to try it myself. How would we actually send commands to the ECU to do an specific task? (e.g. turn on engine, lock/unlock door). I assume the same ELM327 device would work for us to send commands to the ECU.
    It would be pretty cool to control some features of my car from my phone.

    • Hi Phil,

      Unfortunately getting the commands and knowing what the command will exactly do is the toughest part here. Easiest method first would be to search in forums for your particular make and model to see what others have already done. Also, I suggest looking up at the model’s service manual (again, if you can find one) to find out of any clue you can make out, and work from there.

      If you have access to a pass-thru cable, it’s slightly easier as there are many manufacturer specific diagnostic tools (such as Toyota’s Techstream, Honda’s HDS, etc) that you can use to ‘retrieve’ some said commands. Once you have successfully have your laptop talking to the car, you can ‘sniff’ the commands going back and forth which you can apply these said commands from your phone. With that being said, having a bit more computer literacy than the average person is highly recommended at this point.

      Hope that helps.

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