You can read and write a Gen 3 LS PCM for about $100. Maybe $50 if you go the cheap route. The software is free — you’re only paying for the cable.
Software (free)
PCM Hammer or LS Droid. I like PCM Hammer.
Hardware (the only thing you actually pay for)
👉 OBDLink MX+ — what I use. Bluetooth, works with iPhone, Android and Windows. You might have to downgrade the firmware via the phone application before it’ll behave with PCM Hammer.
👉 OBDLink LX — around $50. I’ve heard the LX can write as well, and it’s cheaper. Android only. If you’re trying to keep this genuinely under $100, start here.
Using PCM Hammer
Honestly, the shit is a breeze.
Connect to the OBDLink MX+ with your laptop over Bluetooth. Open PCM Hammer and read the instructions — it’s super important that you do. Make sure your car battery is charged before you start anything.
Side note on writes, and this one matters
Most actions are safe. The scary ones are the full writes.
Almost every other option is recoverable. A full PCM write is not, sometimes — full writes always carry a possibility of destroying the PCM. Keep a spare nearby before you do your first one.
The good news: after your first full write, every change you make afterward can just be a calibration write. Those are the safe ones.
For what it’s worth, I’ve done 30+ writes with PCM Hammer on the same PCM and nothing has broken yet. But “yet” is doing work in that sentence.
Editing the tune with TunerPro
Once you’ve done a full read of your PCM, download TunerPro RT and find the XDF file for your PCM OS.
You find it by searching the OS number and looking for the .xdf extension. Example Google search:
OS12212156 filetype:xdfOr just search the OS number on its own, which usually yields more results.
The XDF doesn’t contain your tune — it organizes and defines all the data structures inside the .bin file you read off the PCM. It’s the map that tells TunerPro what each block of bytes means.
After that, making edits is easy. But you have to know about cars to make good ones. If you don’t know what you’re looking at, Google it and learn what’s going on before you change it. Make your edits, then write your calibration back with PCM Hammer.
Be careful — things can break at any moment.
The one thing that isn’t free
You can read and write a PCM on a $50 adapter. What you cannot do for free is know your actual air/fuel ratio, and a stock narrowband O2 sensor will not tell you. It only resolves tiny changes around stoich, because that’s all GM built it to do.
👉 Innovate LC-2 wideband controller kit with Bosch LSU 4.9 sensor
This is the real cost of the hobby. Budget for it before you start changing fuel tables — I explain why in Part 1 of the beginner start.
What I actually run now
A combo of the above and HP Tuners. I use PCM Hammer to make changes and write them, and HP Tuners to scan, poll the PIDs and read my wideband, then make adjustments off that data.
You don’t need HP Tuners to start. You do need the wideband.
Where to go next
If the terminology in here went past you — PCM vs ECM, MAP vs MAF, what fuel trims are — start with Tuning Gen 3 Super Beginner Start Part 1 and Part 2.
Still choosing a long block? Best LS engine years for boost.
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