Bosch EDC17C46 guide for VW Golf, Skoda Octavia, Audi A4 and SEAT Leon 2.0 TDI ECUs

The unit on the bench came out of a Passat. The Bosch label reads 0281017946, the VW part number is 03L906018PA, and the owner wants the car back on stock software because a remap from another shop has started throwing boost faults. Before any tool gets plugged in, the job is to match three things to a clean original read: the Bosch hardware number, the VW part number with its four-digit software version, and the Bosch 1037 software number. Get those right and the rest is routine. Get one wrong and you’re writing a file meant for a different gearbox, a different power output or a different car.

That’s most EDC17C46 work in a nutshell. This Bosch unit runs a big share of the VAG 2.0 TDI common-rail engines of the EA189 generation, so it turns up in Golfs, Octavias, A4s, Leons, Passats, Tiguans and a long tail of related models. Our catalogue currently lists 712 published EDC17C46 files, and nearly all of them are original reads. The sections below use that catalogue data to show how to identify the unit, which vehicles and engine codes appear, what the numbers look like in practice, how the files were read and which problems keep coming back to the bench.

How to recognise an EDC17C46 on the car and on the bench

The quickest confirmation doesn’t need the ECU out at all. Connect VCDS or ODIS, open the engine electronics and read the identification. On an EDC17C46 car you’ll see a VW part number built on the base 03L906018, followed by one or two suffix letters and a four-digit software version, for example 03L906018PA 9978 or 03L906018LG 2075. On most versions the identification also names the unit as an EDC17 variant, but the part number base is the more reliable check.

Physical location varies with the platform. On most of the transverse-engine cars (Golf, Octavia, Leon, Caddy, Touran, Tiguan) you’ll find it either under the scuttle panel in the plenum area or near the battery tray, depending on model and year. On the longitudinal Audis (A4, A5, A6, Q5) it’s usually in the plenum area below the windscreen. Check the workshop information for the exact car before you start pulling trim, because the connector and bracket layout differs.

The label fields that matter

Once the unit is out, the Bosch label carries most of what you need. If you’re not used to reading them, our guide on how to read ECU label numbers covers the general layout. For EDC17C46 specifically, these are the fields to write down:

Field	Examples from our files	What it tells you
Bosch hardware number	0281016374, 0281017946, 0281018660	Ten digits starting 0281, the Bosch prefix for diesel control units. Identifies the physical board, not the software.
VW part number	03L906018PA, 03L906018KL, 03L906018AN	The 03L906018 base plus suffix letters. On most VAG applications the suffix separates variants such as power output, gearbox and body type.
Software version	9978, 9979, 6638, 2075	The four digits after the part number. This changes when the ECU is updated, so the label can be out of date.
Bosch software number	1037536214, 1037522945	Ten digits starting 1037. The most precise identifier of the actual software in the flash.
Bosch SW part number	10SW070308	Seen on some labels and tool readouts. Useful as a cross-check when the 1037 number is hard to read.

Hardware number patterns in our catalogue

The hardware numbers tagged most often in our EDC17C46 files are 0281016374 (7 files), 0281017946 (5 files), 0281016674 (4 files) and 0281018346 (4 files), followed by 0281018577, 0281018660, 0281017945 and 0281019895. Those counts look small next to 712 files, and there’s a reason. Most of the catalogue was read over OBD, and an OBD read doesn’t see the paper label, so a lot of files are listed by software identification only. Don’t assume a file is missing just because your hardware number doesn’t appear in the tags.

More importantly, one hardware number covers many software variants. In our catalogue 0281016374 appears on a Passat with 03L906018BG and on a Touran with 03L906018MK. 0281016674 turns up on a Caddy with 03L906018NG, another Caddy with 03L906018NF and a Touran with 03L906018NN. 0281017946 is on a Passat with 03L906018PA and a Tiguan with 03L906018LK. Same board, different calibrations. The hardware number tells you what you can read the unit with; the part number and software numbers tell you which file belongs in it.

Software number patterns

The software identifications that repeat most often in our catalogue are 03L906018KL 9978, 03L906018BG 9978, 03L906018HT 9978, 03L906018MQ 9978, 03L906018PA 9978, 03L906018SK 9978, 03L906018LK 9977, 03L906018HH 9956, 03L906018LB 2025, 03L906018LG 2075, 03L906018NG 6638 and 03L906018PA 4007. Notice how often the 997x versions come up across different part numbers. Those later versions are common on cars that have had dealer software updates, which is one reason the label and the ECU readout sometimes disagree. The Audi files show a different pattern again, with versions such as 3110, 3112 and 3113 on 03L906018HT, KL and LB.

Cars and engines in our EDC17C46 catalogue

Almost all EDC17C46 applications in our catalogue are VAG group cars with the 2.0 TDI common-rail engine. The table below groups the files by brand. VW and Volkswagen are separate tags in the shop, so they’re merged here (508 plus 10). The engine codes in the third column are the ones attached to the sample files we reviewed for this guide, not a complete list for each brand. Model counts only include files tagged with a specific model, which is why they don’t add up to the brand total.

Brand	Models (files in our catalogue)	Engine codes seen on sample files	Files in our catalogue
VW	Golf (284), Passat (14), Tiguan (13), Caddy (5), Passat CC (2), Sharan (2), Touran (2)	CFFA, CFFB, CFHB, CFHC, CFHD, CLCA	518
Skoda	Octavia (90), Super B (9)	CFHA, CFHC, CFFB, CFGB	99
Audi	A4 (64), Q5 (6), A6 (3), A5 (2)	CJCA, CGLB, CGLC	75
SEAT	Leon (19), Ibiza (1)	CLCB	20

The Golf dominates, which matches what most workshops see: the Golf 2.0 TDI of that generation was built in huge numbers and plenty of them are still in daily use. The Octavia and the A4 follow. The Audi files deserve a separate note. The longitudinal A4, A5, A6 and Q5 use different engine codes (the CGL and CJC families in our data) from the transverse cars, and their files are not interchangeable with Golf or Octavia software even though the part number base is the same.

Engine codes by file count

Engine code tags give another way into the catalogue, and they’re often more useful than the model name when a customer only knows the engine code from the service book or the sticker in the boot.

Engine code	Files in our catalogue	Engine code	Files in our catalogue
CFFB	173	CFHF	16
CFHC	72	CLCA	15
CFGB	64	CFHD	13
CFFA	63	CGLD	13
CGLC	30	CJCB	13
CJCA	25	CJCD	13
CFGC	24	CFHA	11
CLCB	19	CFJA	11
CLJA	17	CGLB	10

Smaller groups in our catalogue include CGLA, CLLA and CFFE (8 each), CFFD (7), and CFHB, CJCC and CMGB (6 each). One practical warning: an engine code doesn’t prove which ECU is fitted. On EA189 2.0 TDI engines VW also used Continental PCR2.1 units, which carry 03L906022 part numbers on most versions, so the same engine family can come with either supplier depending on model and production date. Check the part number base before you order anything.

Example EDC17C46 files from the catalogue

Here’s a cross-section of real listings: different brands, different hardware, and a few tuned and DPF/EGR files next to the originals. Where the product title doesn’t state a hardware number or a 1037 number, the cell says so. Numbers are copied exactly from the listings.

Vehicle (engine where tagged)	Hardware no.	Software no.	Bosch SW no.	File type
VW Golf	0281016406	03L906018BB 7818	1037510943	Original file
VW Golf (CFFB)	not stated	03L906018AB 9041	1037516680	Original file
VW Passat CC (CFFA)	not stated	03L906018QA 4004	1037526305	Original file
VW Passat	0281017946	03L906018PA 9978	1037536214	Original file
VW Tiguan	not stated	03L906018LG 2075	1037519357	Original file (flash dump)
VW Tiguan	not stated	03L906018LG 2075	not stated	Chip tuning, DPF off, EGR off
VW Tiguan	0281017946	03L906018LK 9977	1037561714	DPF off, EGR off
VW Caddy	0281016674	03L906018NG 6638	1037536608	Original file
VW Caddy (Vmax tuned)	0281016674	03L906018NG 6638	not stated	Chip tuning
VW Sharan	not stated	03L906018HH 9956	1037526396	Chip tuning (stage 1, DPF/EGR off)
VW Touran (CFHC)	0281016374	03L906018MK 9977	1037560911	Original file
Skoda Octavia (CFHC)	not stated	03L906018AN 6779	1037508235	Original file
Skoda Super B (CFGB)	0281019905	03L906018RQ 5408	1037532861	Original file
Audi A4	0281019895	03L906018SK 9978	1037532876	Original file
Audi A4	0281018577	03L906018HT 3110	1037522942	Chip tuning
Audi A5 (CGLC)	0281018660	03L906018KL 9978	1037522945	Original file
Audi A6 (CGLC)	0281017945	03L906018LB 3113	1037522918	Original file
Audi Q5	0281017838	03L906018MQ 9979	1037521635 (10SW070308)	Original file
SEAT Leon (CLCB)	not stated	03L906018EH 7021	1037508283	Original file
SEAT Ibiza	0281016310	03L906018A 6749	1037508246	Original file

A few things stand out once you look at the rows side by side. The A5 file with 03L906018KL 9978 carries the same 1037522945 number that appears on another A5 listing with version 3112, so the four-digit version and the 1037 number don’t always move together in how files get labelled. Match both against your own read. The Passat file with 0281017946 and 03L906018PA 9978 1037536214 is also listed under the Passat CC with identical numbers, because it’s the same software. Model names in titles are a search aid; the numbers decide compatibility.

Some Skoda Super B and Passat CC listings sit on product addresses that start with “vw-golf”. That’s a quirk of how they were created in the shop, not a sign of a mislabelled file. The title and the numbers are what count.

Which EDC17C46 file does the job need?

For this family the catalogue is heavily weighted towards stock software. Today it lists 707 files in Original File, 4 in Chip Tuning, 2 in DPF Off and 2 in EGR Off. Some tuned files sit in more than one category, so don’t add those numbers together. Here’s when each type is the right call.

Original files

An original read is the one every workshop ends up needing sooner or later. Typical reasons:

• A car arrives with someone else’s remap and the owner wants it back to standard, for a sale, a warranty conversation or an inspection.
• A previous write failed and the only backup is corrupt, or there’s no backup at all.
• You’re building a tune yourself and want a known-good stock file for the exact software version as your reference.
• A used ECU from a breaker has the wrong software for the car, and you need the correct calibration for the customer’s part number before adapting it.
• You want to compare a suspicious read against stock to see what was changed.

The rule is simple: the part number suffix, the software version and ideally the 1037 number should all match the car. A Golf file with the right hardware number but the wrong suffix may start and run, then set gearbox, cruise control or emissions faults because it’s calibrated for a different variant.

Tuned files

The handful of chip tuning files in this family are built on specific software, such as the Audi A4 file on 0281018577 03L906018HT 3110 1037522942 or the Caddy Vmax file on 03L906018NG 6638. They only belong on an ECU with the same software. And a tuned file won’t cure an engine that’s already down on boost. Smoke, a sticking VNT actuator, a split intercooler hose or tired injectors will get worse with more fuel, not better. Do the basic checks (live data for boost, MAF, rail pressure and injector corrections) before you write anything.

DPF and EGR files

The DPF off and EGR off files listed here, for example on the Tiguan with 03L906018LK 9977 and 03L906018LG 2075 and the Sharan with 03L906018HH 9956, are for off-road, export and motorsport use. Removing or disabling the particulate filter or the EGR system isn’t road-legal in the EU, the UK and many other countries, and a car on the road with them disabled can fail inspection and void insurance. There’s a technical point too. A blocked DPF is often a symptom. A faulty differential pressure sensor, a leaking injector or a car that never gets a long run will still be a problem after the filter is gone.

Immo off and virgin files

At the moment our EDC17C46 catalogue doesn’t list separate immo off or virgin files; the shop-wide immo off and virgin categories cover other families. If a job needs one, send a request with the full read. Immo off work should only be done on a vehicle the customer owns and can prove they own. For a replacement ECU on these cars, cloning the original unit or a proper immobiliser adaptation is usually the cleaner route (more on that below).

Reading and writing EDC17C46: OBD, bench and boot

The tool tags in our catalogue show how most people handle this ECU. Of the files with a tool recorded, 671 were read with KESS V2, 18 with Flex, 9 with New Trasdata and 1 with KTAG, plus one listing that names New Trasdata, PCM Flash and KTAG together. In other words, OBD reading is the everyday method on EDC17C46, and bench tools come out when OBD isn’t enough. For a general explanation of the three access methods on this generation of Bosch units, see our article on OBD, bench and boot mode on EDC17 and MED17.

OBD

For a straightforward stock restore or a tune on a car that runs, OBD is usually the fastest route. The ECU stays in the car, nothing gets opened, and a tool like KESS V2 reads the areas the diagnostic protocol exposes. The limitation is what an OBD read contains. On most versions it’s enough to write back through the same tool, but it isn’t a full backup of the flash and EEPROM, so it won’t help you clone the unit or recover immobiliser data later.

Bench

Bench mode means the ECU comes out of the car and the tool connects to the main connector pins on the desk, with its own power supply. On most EDC17C46 versions current bench tools such as Flex, KTAG or New Trasdata can read the flash and the EEPROM without opening the case, depending on tool and software version. This is the method to use when you need a full backup, when OBD won’t talk to the ECU, or when you’re preparing a clone.

Boot

Boot mode means opening the housing and connecting to the board with the tool’s boot adapter. It’s the fallback for a unit that won’t respond on OBD or bench, typically after a failed write. The housing on these units is sealed, so take your time opening it, protect the board from static and don’t lever against components.

Cautions that apply every time

• Power supply. Use a proper stabilised supply on the car or on the bench, not a basic battery charger. Voltage dips during a write are the most common cause of a dead ECU.
• Full backup first. Before writing anything, save a complete read of flash and EEPROM (bench or boot if you can), label it with the car’s registration or VIN and store it somewhere other than the laptop.
• Checksums. Most master tools correct checksums on write, but if a file has been edited in another program, make sure the checksum has been corrected before it goes back in. A wrong checksum usually means a no-start.
• Tuning protection. Depending on software version, VAG EDC17 units can carry tuning protection that blocks a modified write over OBD. Your tool will normally report it on connection. Our article on TPROT on EDC17 and MED17 explains what it does and why it matters.
• Keep the car quiet. Switch off lights, blower and radio, stop the laptop going to sleep, and don’t open doors or unplug anything during an OBD write.

Bench notes and typical EDC17C46 faults

These are the jobs that land on the bench most often with this unit, with what to check first. Details vary by software version, so treat them as starting points rather than fixed procedures.

Failed or interrupted flash

The classic case: the write stops halfway, the dash lights up and the engine won’t start. Don’t keep cycling the ignition or retrying blindly. First try the recovery option in the same tool you used for the write, over the same connection. If the ECU no longer answers on OBD, pull it and work in bench mode, and if bench fails too, go to boot. The recovery file should be your own full backup or an original that matches the part number and version exactly. Our guide to recovering a bricked ECU after a failed flash goes through the sequence in more detail.

Label says one version, ECU reports another

Very common on EDC17C46. The label was printed at the factory; the software may have been changed since, either by a dealer update or by a tuner. Many EA189 diesels also received a dealer software update as part of the emissions service campaign, which changes the software version. Always go by what VCDS, ODIS or your flashing tool reads from the ECU, and use the label only as a starting point. If you order a file based on the label alone, you may end up with the pre-update software.

Swapped or used ECU

A second-hand EDC17C46 from another car won’t simply bolt in. The immobiliser data lives in the EEPROM, and the variant coding in the software has to suit the car. On most versions you have three honest options: clone the customer’s original ECU onto the replacement (same hardware, full flash and EEPROM copied across), adapt the replacement to the car’s immobiliser through the dealer’s online system, or use a tool that can handle the immobiliser data for this family. Writing only the flash from the old ECU will fix the calibration but not the immobiliser, so the car will crank and cut.

Limp mode or faults after a remap

If a car goes into limp mode after tuning, look at the mechanical side before blaming the file. Check boost against specified values in live data, look for a sticking turbo actuator or a split boost hose, check the MAF readings and the EGR valve, and look at injector correction values. If a DPF or EGR file was written but the car is still logging faults, the related hardware may still be connected and reporting, or the file doesn’t match the exact software. Writing the original file back is a quick way to test whether the problem is the tune or the engine.

Right hardware, wrong part number

Because one hardware number covers several variants, it’s easy to write a file for the right board and the wrong car. A Caddy file on a Touran with the same 0281016674 hardware, or a manual-gearbox calibration on a DSG car, may appear to work until the gearbox, cruise control or glow plug system starts complaining. If a car behaves oddly after a stock restore, recheck the part number suffix first.

Questions workshops ask about EDC17C46

Is the EDC17C46 the same as the EDC17C64?

No. The digits look similar, which causes a lot of confusion, but they’re different units for different engine generations. EDC17C46 is the EA189 2.0 TDI unit with 03L906018 part numbers. The later EA288 engines moved to other units, including EDC17C64, with 04L-prefixed part numbers on most versions. Check the part number base and you won’t mix them up.

Can I use a file listed for a different model?

Yes, if every number matches. Our catalogue has the same 0281017946 03L906018PA 9978 1037536214 software listed under both the Passat and the Passat CC. The model name in a title is just how the file was catalogued. If the part number, software version and 1037 number match your read, it’s the right file.

My hardware number isn’t in the hardware tags. Does that mean there’s no file?

Not necessarily. Most of our EDC17C46 files were read over OBD with KESS V2, and those reads identify the software, not the label. Search by the 03L906018 part number and the software version instead, or by the 1037 number if you have it. Many listings have no hardware tag at all.

Does a KESS V2 OBD read give me a full backup?

It gives you what the OBD protocol allows the tool to read, which on most versions is enough to restore the car with the same tool. It doesn’t include the EEPROM, so it’s not enough for cloning or immobiliser work. If there’s any chance you’ll need to recover the unit on the bench later, take a bench read as well.

Will an original file clear my fault codes?

Only if the fault was caused by software. Writing stock software removes a bad tune or a corrupted calibration, but it won’t fix a failed sensor, a blocked DPF, a sticking EGR valve or a boost leak. Diagnose first, then flash.

What if a product title lists several 1037 numbers?

Some listings, such as a Tiguan file on 03L906018LG 9979, show more than one 1037 number in the title. Match the number your tool reports as the current software, and if you’re unsure, ask before buying with your read identification to hand.

Do you have immo off or virgin files for EDC17C46?

Not as listed products at the moment. You can request one with a full read from the ECU in question. Immo work is only for vehicles the customer owns, and for most EDC17C46 replacements a clone or a proper adaptation is the better solution anyway.

When your EDC17C46 file isn’t listed

With 712 files in the family there’s a good chance your software is already in the EDC17C46 section of the catalogue, but not every version has been uploaded. If you can’t find a match, use the file request form and include as much as you have: the Bosch hardware number (0281…), the VW part number with its software version (03L906018 plus suffix and four digits), the 1037 software number, the vehicle, the engine code, which tool you read it with, and a full read if you’ve managed to get one. A clear photo of the label saves a lot of back-and-forth, particularly on older units where the print has faded. The more of those numbers line up, the quicker the right file can be found or prepared.