Category Archives: Euro6

Injector Codes

Denso Injector DCRI107890 (Denso part# 095000-7890, Subaru part# 16613-AA020) for Euro 4 Subaru Diesel


Quote from a DENSO document incl. picture below:

Replacing a Diesel Common Rail Injector:
When replacing a DENSO Diesel Common Rail Injector, marked with a compensation code, it is necessary to register the ID code, printed on the upper part of the injector, with a genuine OEM – or DENSO diagnostic tool, into the electronic control unit (ECU). The injector compensation (ID) code is used to compensate injector production tolerances.
Some vehicles also require Small Injection Quantity Learning.

Denso Injector ID graphic

Subaru’s term for injector compensation or ID code is “injector code“. Dealership Subaru Select Monitor (SSM-III or later) software has menu items like “Injector Code Display” and “Injector Code New Registration (SSM to ECM)

First off, the engine control unit has no way of measuring actual injected fuel amount, such technology would be expensive for these kind of small fluid quantities. Due to high common rail pressure, even tiny production tolerances result in unwanted injection quantity variations. Obviously, each injector must be registered using its correct cylinder number so the ECU can apply individual adjustments when it is calculating injections. Basically, the ECU accomplishes desired (target) injection quantity by adjusting the duration of injector drive signal.

Since programmed injector codes as well as any other important data is being saved into an extra EEPROM chip, there is no risk of data loss having the car battery disconnected.

Consequences of Wrong or Missing Injector Codes

According to DENSO:

  • Knocking noise
  • Unstable idle
  • Wiggling during driving
  • MIL (Check Engine Lamp) on

Cylinder numbers – Quick Reference

As for a quick reminder, looking at the front of the car into engine bay, cylinder numbers are:

towards back
  3        4
  1        2
car front (radiator etc.)

Getting Injector Codes via QR Code

Although normally this should not be necessary, injector codes can be read from the actual injector parts even when mounted on the engine and inside the engine bay, therefore not easily accessible. Taking a picture using a mirror tool is relatively easy, no need to disassemble any parts:

Injector QR Cyl2 small

While the injector code label itself is hidden by the (white) electrical connector, its QR code is visible by default.
Make sure the QR code on the photo is as sharp as possible and has sufficient resolution. At the car I usually just try to get high quality pictures. Later on my computer I simply select the best pic, then scan QR info straight off the computer screen using a smartphone.

Using an image manipulation program (i.e. GIMP, PhotoShop) in order to improve the QR code area can result in much better QR detection. In my case, this was not needed as the app can also detect inverted QR (light code on dark background).
Android app tested: “Barcode Scanner” from F-Droid repository. Check settings → Invert scan.

As an example, the following pic is the extracted and improved QR code portion from above picture. I used these steps in GIMP: crop, perspective correction, grayscale, invert, brightness & contrast . You should be able to scan this:

Injector QR Cyl2 processedScanning captured QR code results in a line of text containing 49 characters:


First 19 chars:

  • First four chars “7890” match Denso basic part number.
  • Possibly contains production date “2008-09-11” ?

Injector Code Format

Remaining 30 chars is the exact injector code needed for ECU. These chars must be in hexadecimal (0-9, A-F) form as they are transmitted as 15 bytes to and from the ECU:

Byte index [0..14] Content
0 const, sort of generation ID, verified by ECU:

  • Euro 4: B3
  • Euro 5: B2
  • Euro 6: B6
1..12 12 payload bytes containing correction data, type int8. Each signed byte must be within range [-125, 125]. In other words, the following five bytes are not allowed: 7E, 7F, 80, 81, 82.
13 const 00
14 simple XOR checksum

Resultant properly formatted injector code (left to right, 4 chars per block):

B300    0000
0000    E9EB
EBEC    F300
0000    45


Invalid codes will be rejected! Euro 5+ will return NRC 0x31 (request out of range).
Injector code data is not compatible between common rail system generations due to differing correction points! Euro 4 uses fewer points (10) than E5+ (12). Therefore, for example, programming a Euro 5 injector code into Euro 4 ECU will not work and vice versa.


AFAIK, Denso’s own PC diagnostic software has the ability to read from a QR scanner device, Subaru OEM application SSM-III does not – need to type in codes manually.

Protocols needed for injector code display & registration:

  • Euro 4: SSM2 via Serial
  • Euro 5/6: Extended OBD-II

As far as we know, there is no free/open-source software for this yet.

EcuTek tool probably supports injector coding up to Euro 5.


  • 2017-04: additional notes and details
  • 2016-04-03: Euro 6


Wikipedia: Diagnostic Trouble Code (DTC)
All following DTCs are Subaru specific, applicable to closed-type DPF Boxer Diesel models only, Euro 4, 5, 6 emission standards.
Some of these DPF related DTCs trigger DPF light flashing.

ID Name Comment
P1465 DPF Particulate Overfill
P1466 DPF Substrate Damaged (E4: never gets set?)
P1467, P242F DPF Ash Overfill ≥ 100 %
P1468 Oil Dilution ≥ 10 % ; also see Distance to Oil Change
P1469, P246C DPF Limp-Home Mode Reduces injection quantity and power.
P1471 DPF Pressure Difference Sensor Upstream Piping Trouble (E4: never gets set?)
P1472, P2454 DPF Pressure Difference Sensor (Low)
P1473, P2455 DPF Pressure Difference Sensor (High)
P147B Catalytic Converter and DPF
P2453 Particulate Filter Pressure Sensor “A” Circuit Range/Performance

Related ROM code has not been analyzed completely yet, no guarantees as usual. It is definitely much more sophisticated compared to Subaru petrol ROMs.


  • 2016-10 Added DPF related Euro 6 DTCs.

DPF Light


  • Do consult your car manual! Unfortunately owner’s manuals lack useful details.
  • Please also read our DPF management page.
  • Same DPF light logic in Euro 4/5/6 ROMs.
  • DTC numbers differ across boxer diesel generations.

Applies To

All Boxer Diesel models fitted with closed-type Diesel Particulate Filter (managed DPF), emissions spec Euro 4, 5, 6.

Therefore does NOT apply to early diesel models equipped with open-type DPF (MY 2008/2009 Legacy/Outback). These do not have DPF management at all in software, no sensors, no DPF light, a lot less to worry about!


Constant light means “Soot High Warning“, also called “Vehicle Speed Request“.

According to manual, one should drive for at least 15 minutes at 60+ km/h, providing favorable conditions (exhaust gas temperature high enough) for active DPF regeneration to start (and ideally complete) in order to reduce soot.

Steady light is triggered by single condition:

  • Soot Accumulation Ratio > 85%

According to ROM logic, steady light will turn off when soot drops below 75% (hysteresis).

If there’s any error condition, see below, the error has higher priority, always resulting in flashing mode.


Flashing/blinking means “Error“, any of the four possible conditions can trigger this mode right away – without showing steady light before.
The manual usually states something like: go to Subaru dealership for inspection. Waiting too long might worsen the issue! Mileage driven with light ON can be recorded by ECU and read out with software!

  1. Oil Dilution Ratio ≥ 10% (also sets DTC P1468 Oil Dilution). Remember, as dilution is just a rough estimate, the value and therefore this error can easily be false! Might disappear when dilution drops below threshold due to calculated evaporation, see post Oil Dilution Graph. Dealership might have forgotten to reset oil dilution at oil change – seen this many times on forums.
  2. Compulsory regeneration required, also called “Dealer Visit Request“; e.g. Soot Accumulation ≥ 100%; ECU does not try active regen anymore unless soot drops to normal level
  3. Ash Accumulation Ratio ≥ 100% (also sets DTC Ash Overfill). Need to clean or replace DPF and tell the ECU to reset this value.
  4. DPF Limp-Home Mode (also sets DTC DPF Limp-Home Mode).

DPF Light Control

At ignition ON, the DPF light illuminates for two seconds exactly – light test –  and should stay off afterwards, indicating normal condition. Otherwise see above.

On Impreza Euro 4 / 5, ECU operates DPF light using CAN message 0x600 byte 0 bit 1, bit = 1 means light ON.

Euro 6 just seems to use different CAN IDs and frame contents.

Like we did in above GIF animation, flash rate is 400 ms/400 ms on/off (8/8 CAN messages at 50 ms interval), respectively. There are no other stock flash modes. In the future we’d like to use DPF light for additional purposes e.g. indicating active regeneration by implementing a different flash rate. We already did a patch using DPF light to indicate active regeneration: Diesel ECU Patch v1. For source code see post DPF Light Patch.


  • 2016-10 incorporate Euro 6 findings


Tachometer driven by custom software, engine off, for demo purpose. Needle is at maximum position.

Tachometer redline range is 4,700 – 5,500 rpm. All related subroutines are well known by now. Same source code in all diesel ROMs it seems.

Within normal driving conditions the ECU won’t allow any over-rev because it gradually reduces injected fuel (zero at 4,800 rpm ?). This way over-rev can only be reached by force (mis-shift or faults).

Over-Rev Counters

There are two over-rev counters, triggered by two different RPM levels. Both are considered important therefore saved into EEPROM.

Item Unit MY08 MY09 MY10 MY11
High RPM: Repeated incidents might damage engine.
High RPM Threshold rpm 5,500
High RPM Hysteresis Low rpm 5,250 4,900
Very high RPM: Might damage engine on single occasion.
Very High RPM Threshold rpm 5,900
Very High RPM Hysteresis Low rpm 5,650 4,900

RPM must drop below hysteresis low value to allow next incident to be triggered. Prevents multiple counter increments on single incident.

Reaching five recorded “high” or a single “very high” incident might also turn on MIL.

DTC P0219 Engine Overrunning Failure

Triggered by condition: RPM ≥ 5,150. Confirmed with all models so far, Euro 4/5/6. Also causes freeze frame(s) capture.

High RPM History

Diesel specific, basically meant to acquire additional info. Subaru’s warranty department will probably look at this.

Although diagnostic software lists names like “Highest Over-Rev RPM history”, these actually start tracking within redline already (allowed but to be avoided), obviously don’t mean real over-revs when rpm < 5,500.

Only when above DTC P0219 has been triggered, the high-RPM-history management subroutine activates, tracking highest RPM it sees during incident. Later when DTC condition is not set anymore (=RPM dropped below 4,900) it updates its records, filling in highest engine speed it had seen plus current odometer value.

There are four records: highest and last three incidents.

Each record consists of two parameters and can be retrieved using a Subaru specific protocol:

  1. RPM, UInt8: x*20+4000 [rpm] → lowest possible value is 4,000 meaning NO incident yet!
  2. Odometer1, UInt16: x*5 [km]

Since history subroutine is separated from DTC checking subroutine and both use current RPM as input, it’s possible that when history sub gets to run, the RPM had already dropped < 5,150. So even though history needs the 5,150 rpm DTC threshold, remembered RPM values can be slightly lower, already seen that in practice.

1) It is actually the ECUs internal odometer, does not have to match dashboard odometer driven by combination meter computer! Usually these two odometer values drift off over time, typically 1% or more. Accessing Subaru diesel ECU odometer usually requires ROM specific software knowledge as there is no diagnostic protocol parameter implemented for this.

Injector Learning / Calibration

Applies to all known Boxer Diesel models, Euro 4/5/6.
Injector learning (micro quantity calibration) procedure can improve engine idling (vibrations, noise, fuel economy …). The ECU measures engine speed changes, derives learning values and uses them (for idling only?) from there on.

Tiny fuel injections, achieved through very short pulses, are especially sensitive to mechanical wear inside injectors. Remember, the ECU does not know how much fuel is actually being sprayed into the cylinders. However, by measuring acceleration (crankshaft speed changes) after at each cylinder’s power stroke, it can adjust injection pulses to achieve a balance across cylinders.

Normally, a power stroke consists of two or three individual injections, main injection always being the largest one. For micro quantity calibration, the software does things differently. It divides the necessary fuel to hold engine speed into more and evenly small injections so that only short pulses matter and differences in injected amounts can be compensated.
The entire procedure is done in two ways:

  1. Automatically by ECU when idling (~800 rpm), for example at traffic light stop. Takes roughly a minute to complete. Goes through first 4 pressure levels. ECU will try again if it could not finish.
  2. Compulsory using Subaru dealer software (open source solution is planned). In addition, this mode uses higher common rail pressure, revving the engine up to ~1,200 rpm at 5th pressure level which is not acceptable in auto-mode.

Injector Learning Chart

Either way, the operation causes distinct engine noise due to special injections, easy to recognize. Also altering common rail pressure to the next pressure level causes noise to change.

You can use logging (Subaru specific protocols) in order to monitor related parameters:

  • injector learning status (ON/OFF)
  • injection quantity learning values [ms] (4 cylinders times 5 pressure levels = 20 values; all zeroes means learning has not been completed successfully)
  • mileage after last learning [km]
  • mileage after injector replacement [km]

As usual, all relevant values are being saved into EEPROM.

Automatic Injector Learning Intervals

In theory, ECU wants to do automatic injector learning at these predefined intervals:

# Odometer
1 50 50
2 200 150
3 350 150
4 950 600
5 1,550 600
6 4,550 3,000
7 7,550 3,000

Confirmed by disassembly from Euro 4/5/6 software. As you can see, the interval is being increased up to 3,000 km.

Above odometer values are theoretical because:

  • For the ECU mileage after last learning matters, not any absolute odometer value.
  • If conditions are not met, learning process is being delayed, trying again at next occasion, increasing all further odometer numbers.
  • ECU internal odometer is not very precise, it will drift off from combination meter odometer over time.

Injector Learning Conditions

Basically, engine must be warm, around 80°C coolant temperature. Lots of parameters must be within pre-defined ranges (fuel temperature, accelerator not depressed, battery voltage 12..15 Volts, …).

Video Links

Courtesy of contributors posting their videos.

Automatic learning



  • Adjusting internal variable “mileage after last learning”, i.e. setting to 3000+ km triggers automatic calibration ASAP.
  • Adjusting ECU odometer, i.e. to re-synchronize with dashboard value.

Engine Oil Change (DPF models)

Owners want to be able to change oil by themselves obviously.
On closed-type DPF models (all except MY 2008/2009 Legacy/Outback which are mated with open-type DPF) you’ll need to reset oil dilution parameter as it is calculated (not measured!) by the ECU. Basically active DPF regenerations in particular cause diesel fuel bypass into engine oil. Piston rings cannot seal perfectly.
Not doing a reset could even cause limp-home-mode in the LONG TERM, IF the ECU assumes dilution being too high.

Following info as seen in all managed DPF ROMs so far.

DTC P1468 Oil dilution is being triggered when oil dilution ratio ≥ 10 %. Also results in DPF light flashing.

The engine management software assumes 6.13 kg oil mass and this maintenance operation sets RAM variable “Oil Dilution Amount [kg]” to zero.
The ROM’s internal calculation steps are:

  1. Oil dilution amount [kg]
  2. Oil dilution ratio [%] = 100 * OilDilutionAmount [kg] / 6.13 kg
  3. Estimated distance to oil change [km], via LUT

Also see posts Estimated Distance to Oil Change as well as Oil Dilution Graph.

Oil Dilution Reset

We’ve traced related Euro 4/5/6 ECU-ROM code. Here are all possible options:

Euro 4 (IV)

  1. Diagnostic protocol (SSM2 via Serial only). See post Oil Dilution Reset (K-Line, Euro4). There is no alternative method on Euro 4 models! ¹)

Euro 5 (V), Euro 6 (VI)

  1. Diagnostic protocol (Extended OBD-II only since it is not implemented via SSM2 in ROM)
  2. Manual procedure, check your owner’s manual. You only have 4 seconds to accomplish each steps from D to L:
    1. Transmission in neutral
    2. Apply parking brake
    3. Start engine
    4. Depress and hold brake pedal
    5. Defogger ON
    6. Lights ON (step 1 = parking/clearance/DRL lights is enough)
    7. Defogger OFF
    8. Lights OFF
    9. Defogger ON (again)
    10. Lights ON (again)
    11. Defogger OFF
    12. Lights OFF
    13. Release brake. Now the glow light (depicting yellow coil) will flash for a few seconds. Otherwise repeat from step D.
      Glow Light

    Users confirmed this, e.g. Subaru Forester Owners Forum – Oil change on Diesel engine and ECU service reset. We also know the related ROM software subroutines, seems to work as advertised.

1) In theory, we could patch Euro 4 ROMs to add the same Euro 5/6 ROM manual procedure – not a trivial task, though.

Estimated Distance to Oil Change

Estimated distance to oil change is directly driven by oil dilution ratio. Confirmed in all Boxer Diesel ROMs so far, Euro 4/5/6 spec. (Exception: does not apply to open-style DPF – earliest Euro 4 models).

The term “distance to oil change” is actually misleading. Normally, some time after oil change + reset, oil dilution ration often settles somewhere between 4 and 6% (Euro 4), the lower the better. Do not confuse this with distance till next maintenance! Do consult car manual instead or ask dealership.

The firmware uses a 2D LUT (two dimensional lookup table) and standard interpolation:

ScoobyRom screenshot portion

ScoobyRom screenshot portion

However this x-y table data makes up this perfectly linear relationship:

DistanceToOilChange[km] = 15000 - 1500 * OilDilutionRatio[%]

Distance to oil change cannot get negative because interpolation subroutines don’t extrapolate.

Note that the logging parameter Oil Dilution Ratio [%] (SSM2 0x00027C, x[%]) cannot provide decimal places, as it is a simple integer value without conversion.
Original RAM value however is a 32-bit floating point variable so if you are able to log RAM (advanced, specific ECU ROM definitions required!) you can spot slight changes.

Another and rather easy option is to log parameter Estimated Distance to Oil Change (SSM2 0x00029A, x*100 [km]) and reverse-calculate oil dilution ratio:

10-x/15 [%]

This will provide better oil dilution precision, roughly one decimal place.

Note: Maximum result value is 10 % since underlying value cannot get negative. Use standard oil dilution parameter if you get close to and above 10 %.

Add this to RomRaider logger definitions:

<parameter id="P300" name="Oil Dilution 2" desc="Reverse-calculated from Estimated Distance to Oil Change to get better precision." ecubyteindex="72" ecubit="4" target="1">
    <conversion units="%" expr="10-x/15" format="0.00" gauge_min="0" gauge_max="15" gauge_step="1" />

For newer models that use the new diagnostic protocol, look here: Extended OBD-II

Of course both oil dilution ratio and distance to oil change should be considered rough estimations. So far all Subaru control units cannot measure dilution, there is no suitable sensor attached. Such dilution sensors do exist but add costs, especially development and (reliability) testing. As a result of missing sensor, the ECU must be told to reset oil dilution value when engine oil has been replaced – see Engine Oil Change (DPF models).

10 % oil dilution is critical where ECU will flash DPF light, also stores DTC P1468 Oil Dilution.

We know the oil dilution algorithm in detail and are able to debug issues. Basically, oil dilution gets to increase while active DPF regeneration is being performed. Otherwise it will drop (very) slowly as the ECU estimates oil evaporation. As you might expect, evaporation rate depends on (coolant) temperature, the higher the better. See post Oil Dilution Graph for more details.

Articles regarding oil dilution:


  • 2016-10: confirmed that this also applies to Euro 6 spec
  • 2016-05: added logger.xml snippet