What is an injector compensation code?
An injector compensation code tells the ECU this specific injectors flow rate.
Why are Injector Codes Important?
The ECU will calculate a desired amount of fuel to be injected based on a large number of factors and correction tables. This calculated quantity will be an outcome of 3 critical factors factors:
- Rail pressure (more pressure, more density, more fuel)
- Injector Opening time (longer - more fuel)
- Injector Flow rate
Injector flow rates a mechanical/hydraulic outcome of the physical condition of the injector itself.
The injector compensation code - essentially - gives this answer.
What do the numbers on the code mean?
Using Denso as a reference. The first 2 digits tell the ECU the calibration protocol it is using. For this reason, it's usually great for identifying injector part numbers.
The digits themselves are in hexadecimal. This means the ‘numbering sequence’ is 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, a, b, c, d, e, f, making 16 options per ‘location’ (base 16 maths).
The 26 digits in the middle are made up of 2-digit (signed 2’s hexadecimal) groupings, allowing for 13 correction points. Different protocols have different testing points (rail pressure and opening time) so there are usually many 00s (denoting either no change or no test).
The last 2 digits (next to the shape - in the case above is a circle) are known as a ‘CheckSum8 Xor’ (It's a software coding ‘check’ - not relevant for us).
How does the Denso code work?
For each calibration point, there is a designated rail pressure, opening time and target fuel value. The 2-digit groupings are actually telling the ECU how many microseconds the ECU needs to add or subtract to this injector in order to make the target fuel quantity.
So a 00 code means nothing added or subtracted. A 0b code means adding 11uS, a 22 code means adding 35uS, a F0 code would be subtracting 16 microseconds…. You get the point.
Example. This imaginary correction point on the table is a fuel quantity of 30mm cubic / stroke, at 800 bar and around 660 microseconds. If an injector has a code of 00, it needs 660 microseconds to get this fueling. If it has code EF (-17) - This injector only needs 643 microseconds to get this fuel quantity right, OR, if it has a code of 2A (+42) for this point, it needs 702 microseconds to get the fueling right.
Frequently Asked Questions
Will the engine run if I don’t code them? Yes.
Will it run well? Maybe.
Is it hard to code injectors? No.
Should you? 100% yes!
Haha, sorry for the basic comments there, but you get the point. If you’ve just paid something like $2000 to have injectors replaced, It is silly to not do the job properly.
Get it done, enjoy a quieter and smoother engine.
IMPORTANT You’re going to need a scan tool – a good one! So if you have access to one, sure, as its not a hard process.
The specific process is unique to each scan tool and vehicle, but if you’ve used one before, it’s simple enough to work it out. Contact the scan tool manufacturer for your specific instructions.
Helpful Hints
From here, I suggest trying to input the injector codes into the ECU before you fit them into the engine. It's much easier this way, and if you’ve somehow got the wrong injectors, you’ll know before you’ve fitted them and bought them. Also, it's bloody easy to make a mistake. It's just easier to have them with you when working on the scan tool.
Once you’ve entered in the codes, PLEASE MAKE SURE YOU KNOW WHICH INJECTOR IS MEANT TO GO IN WHICH CYLINDER! We use a permanent marker and just mark a 1-4 on the white QR code section or on the outside like shown below.
