Bosch EDC15 on the 2.5 V6 TDI

Bosch EDC15VM+ — VAG 2.5 V6 TDI (VP-generation EDC15). This is the VP (Verteilerpumpe / distributor-pump) branch of the EDC15 family, distinct from EDC15P/P+ (Pumpe-Düse unit-injector) and EDC15C (which is in fact a COMMON-RAIL variant used on BMW M47/M57 DDE, Mercedes CDI OM6xx, PSA 2.0/2.2 HDi). The 2.5 V6 TDI is the flagship VP application.

Reference - updated 7 October 2026

The ECU hardware

MCU: Infineon/Siemens C167 16-bit (Intel/little-endian core; boxes are typically C167CS-LM class, some CR). Program and calibration live in an EXTERNAL parallel NOR flash (commonly an AMD/ST/Spansion Am29F400-series PSOP, 4 Mbit = 512 KB / 0x80000; a few hardware revisions differ, so confirm the actual marked chip on the board, and note that some tools report ~1 MB when they also capture the C167 internal region). The C167 also has an internal bootstrap-loader (BSL) ROM used for bench recovery. Adaptation plus the immobiliser/component-security data (login PIN / SKC / 7-digit CS) sit in a SEPARATE small serial EEPROM - commonly an ST/Microchip 95040 (4 Kbit/512 B) or 95080 (8 Kbit/1 KB) SPI part, or a 24C02/24C04 I2C part depending on hardware revision; read the actual chip marking rather than assuming a part number. The board is a Bosch 0281 0xx xxx / VAG 059 906 018 x (2.5 V6) or 4B0 907 401 x-style part. Verify the exact 10-digit VAG and Bosch numbers AND the flash/EEPROM chip markings before flashing.

Fuelling and load sensing

Diesel. Bosch VP44 radial-piston ELECTRONIC DISTRIBUTOR injection pump — a single pump feeding all 6 cylinders via a rotating distributor head, with a high-pressure metering solenoid setting fuel quantity and a separate electronic timing device (timing piston) setting start-of-injection angle. Delivery = injected-quantity (mg/stroke) demand translated to pump solenoid duration + SOI angle. CRITICAL FOR TUNING: NO common-rail rail-pressure map exists to raise — fuelling headroom is bounded by VP44 mechanical/thermal delivery, the hot-film MAF measurement range, and the smoke/torque limiters. The VP44 head/solenoid/timing-piston is the real fuelling ceiling and a known failure point.

How this ECU is read and flashed

Read/write is normally BENCH or BOOT (C167 bootstrap/BSL) mode, not casual OBD. OBD/KWP2000 (SID 34 requestDownload / 36 transferData / 37 transferExit) programming IS possible with the right tool (MPPS, Galletto 1260, KESS), but full-flash READ over OBD is often restricted and immo/PIN complicates OBD writes, so pro practice is bench/boot. BENCH/BOOT: open the ECU, apply a bench harness, enter C167 bootstrap by pulling the boot-config strap at reset (board-specific — the flash/P0L strap point varies by PCB rev, verify it for the exact board; do NOT assume a fixed 'pin 24'), then upload a serial loader over K-line to R/W the external NOR flash AND the serial EEPROM. Boot mode is IMMO-IMMUNE (direct flash access regardless of immo state) — the reliable, brick-resistant path. Tools: KT200/KTAG, MPPS v16 (boot), Galletto, FoxFlash, KESS, CMD, and the open EcuProg7 / C167BootTool (handles 95040/95080/24C0x EEPROM + external flash). IMMO: login PIN/SKC + component-security (7-digit CS) live in the SEPARATE serial EEPROM (95040/95080/24C0x); for bench-run, ECU swap or immo-off you must read/align it — VAG EDC15 immo utilities read the PIN/CS from an EEPROM dump and can set immo-off. ALWAYS dump the EEPROM (and keep an untouched backup) before any immo edit. Internal refs: vagpulse-me7-bootmode-bsl (C167 BSL), vagpulse-kwp1281-eeprom-read.

Engine codes in this family

• AFB (110 kW/150 PS, 310 Nm) — Audi A6 C5, A8 D2 (early V6 TDI)
• AKN (110 kW/150 PS, 310 Nm) — A4 B5, A6 C5, A8 D2
• AKE (132 kW/180 PS, 370 Nm) — A6 C5, A8 D2, allroad
• BAU (132 kW/180 PS, 370 Nm) — A6 C5, allroad
• BDH (132 kW/180 PS, 370 Nm) — A6 C5
• AYM (132 kW/180 PS, 370 Nm) — A8 D2
• BDG (120 kW/163 PS, 310 Nm) — A4 B7 (later 163 PS variant)
• BCZ / BFC - 2.5 V6 TDI, roughly 120-132 kW (163-180 PS) depending on application; confirm the exact PS per VIN/car. Note that the 2.5 V6 TDI was not fitted to the VW Phaeton - the Phaeton's diesels were the 3.0 V6 TDI common-rail and the 5.0 V10 TDI.
• NOTE: verify each specific code against ETKA/VIN — several 163 vs 180 PS sub-variants (BCZ/BFC/BDG/AYM) are easily swapped in secondary sources.

Staging - what each stage really gives

• stage1 - Software only. Raise driver-wish IQ; raise the MAF smoke limiter and torque/full-load limiter in LOCKSTEP; raise boost target ~+0.15–0.25 bar with the boost limiter and N75 duty moved together; light SOI optimisation. Typical outcomes: 150 PS → ~185–200, 163 PS → ~195–210, 180 PS → ~215–225 PS; torque +60–100 Nm (~+20–30%), matching mainstream tuner figures. Bounded by VP44 delivery, hot-film MAF range, the single stock VNT turbo, and the stock clutch/auto torque cap — keep it clean (no visible smoke, EGT/AFR margin held).
• stage2 - Stage-1 map strategy + bolt-ons: larger/front-mount intercooler, freer intake and filter, de-cat/larger downpipe and exhaust, EGR delete (off-road/illegal on-road), sometimes an uprated MAF/housing. Lower EGT and backpressure allow slightly more fuel/boost safely and more sustained power. ~210–240 PS; much of the benefit is reliability/consistency (EGT headroom) as much as peak. Uprated clutch strongly advised on manuals; monitor EGT (no factory sensor).
• stage3 - Hardware to move the walls: hybrid/larger VNT turbo, blueprinted/uprated VP44 (larger element) + larger injector nozzles, uprated clutch + (ideally) upgraded dual-mass or single-mass flywheel on manuals, or a built/torque-limit-raised ZF 5HP19 auto, plus bigger intercooler. Realistically ~230–260 PS reliably; ~280–300 PS is possible only with a fully upgraded pump/injectors and is at the edge of VP44 durability. Diminishing returns — VP44 flow and turbo/driveline are the hard walls; without pump + injector + clutch upgrades you cannot safely pass ~240–250 PS.

Safety limits

• Pre-turbo EGT: sustained < ~750–780°C, brief peaks ≤ ~800°C. There is NO factory EGT sensor — protect via AFR/smoke margin, and fit an actual pyrometer + wideband for any Stage 2/3 development.
• AFR/smoke: keep full-load lambda lean of ~1.15–1.2 (never richer than ~15–16:1). Fuel must stay within MAF-measured air. Black smoke = over-fuel = soot + EGT spike. Rule of thumb: max IQ ≤ air_mass / 14.5 / 1.2 (diesel stoich ~14.5).
• MAF sensor saturation: the stock hot-film MAF has a finite clean measuring range. Once airflow saturates the sensor, the smoke limiter is fed a wrong (flat/low) air figure and will either hard-clamp fuel or, if the MAF curve was rescaled to hide the saturation, allow dangerous over-fuelling. Do not tune past the MAF's range without a correctly-sized larger MAF/housing and a proper re-linearisation - never fudge the MAF (LMM) curve to mask saturation.
• Boost: stay inside the single VNT turbo's safe map — target peak ~2.1–2.3 bar absolute (~1.1–1.3 bar gauge), brief spikes to ~2.4 bar only, TAPERED after ~4000–4500 rpm. Raise the boost LIMITER in step or you trip overboost limp (P0234);
• VP44 pump: do NOT over-drive solenoid duration/delivery beyond pump capability. The VP44 head/solenoid/timing-piston is a known failure point and IS the real fuelling ceiling (no rail pressure to lean on); excess delivery = accelerated wear/failure.
• Torque-monitor LOCKSTEP: raise driver-wish, smoke limiter, torque limiter AND boost limiter TOGETHER. Editing only driver-wish makes the ECU clamp fuel and can flag a torque-model deviation → limp. Respect and shape (don't flat-scale) the torque limiter — it is the safety net for driveline/pump/turbo.
• Driveline - clutch AND dual-mass flywheel: the manual clutch is rated to about 370 Nm and will likely slip past roughly 400-450 Nm. Shape torque to avoid spikes, and upgrade the clutch plus DMF (or convert to a single-mass flywheel) for Stage 2 and above.
• Automatic: the ZF 5HP19 has its own gearbox torque-limit/protection map, and no torque rating is published for it; going past what the box accepts stresses it or torque-caps fuel in gear. Raise the box map only in step with engine torque and within the transmission's real limit.
• SOI/timing: keep timing changes small and logged — over-advanced SOI = harsh combustion + mechanical/EGT stress; over-retarded = high EGT + smoke.
• Integrity: recompute ALL affected checksums after edits and verify a fresh re-read matches BEFORE running; never hand-poke stored checksum bytes. Keep an untouched stock flash AND EEPROM backup.
• Emissions: no DPF on these engines (no regen thermal limit to manage), but EGR delete is emissions-illegal on public roads; gate it behind an explicit off-road acknowledgement.

Every car using this platform (7)

Stock power and typical remap figures per car. Stage results assume a healthy engine on good fuel.

How confident is this?

Well established: the EDC15VM+ family and the C167 MCU; the VP44 radial-piston distributor pump (so there is no common-rail rail-pressure map, and it is not Pumpe-Duse); an external-NOR full-flash tuning image with simple additive multi-region checksums that free tools auto-correct; the map/axis storage (adjacent maps, self-describing headers, shared normalizers, factor+offset decoding) and the definition/axis-signature/diff/live-log location workflow; the fuelling hierarchy (driver-wish, then smoke limiter, then torque limiter, lowest wins) and the need to keep those in lockstep; bench/boot C167-BSL flashing being immo-immune, with the immo/PIN held in a separate serial EEPROM; and the diesel EGT/smoke/AFR/boost safety envelope.