P2002, P2452, P0401 After DPF or EGR Removal: Why Codes Stay and What a Proper File Does

A Vectra C 1.9 CDTI came in last week with the DPF cut open and welded shut, an EGR blanking plate, and a file from somewhere that ‘turned off the DPF’. On the tester: P2002, P244A, P0401 and P2458, and the engine held at 3,000 rpm with no boost. The owner was told the codes were ‘normal after a delete’. They aren’t, they’re the sign of a quick edit rather than a solution.

The codes and why each one is still there

• P2002 (DPF efficiency below threshold bank 1): the ECU compares the pressure drop across the filter with what its soot model expects. Empty can, near-zero pressure drop, model still running: efficiency ‘too low’. A file that disables only the regeneration leaves this test alive.
• P244A (differential pressure too low) and P244B (too high): plausibility on the differential pressure sensor. Sensor unplugged gives P2452/P2453 (circuit) or P2454/P2455 (low/high). Sensor plugged in on a gutted filter gives P244A. Either way the sensor’s evaluation must be switched off, not just the code.
• P2458 (regeneration duration) and P2463 (soot accumulation): the soot model kept counting because the model itself wasn’t disabled. Once it passes the limit the ECU requests a regen, can’t complete it, and eventually limps.
• P0544/P0545/P0546, P2031/P2032/P2033, P242A to P242D: exhaust gas temperature sensors 1, 2 and 3. Removed with the DPF and unplugged, they throw open-circuit codes. Left fitted in the pipe they usually pass, unless the ECU expects the regen temperature rise and never sees it.
• P0401 (EGR flow insufficient): the ECU commands EGR, sees no air mass drop at the MAF. A blanking plate with the valve still active, and the EGR strategy still on, gives this every drive. P0403/P0404/P0405 appear when the valve is unplugged (circuit and position feedback).

Quick edit vs proper file

A quick edit disables the regeneration request and a handful of DTC entries. Costs five minutes, works for a week. A proper DPF off disables the soot and ash model, the regen strategy including the post-injection tables, the pressure sensor evaluation and its plausibility, the temperature model for the filter and the reactions (torque limit, lamp, regen inhibit) tied to them, then sets sensor substitute values so unplugged sensors don’t matter. A proper EGR off zeros the EGR maps across the range, disables the flow monitor and the position control (or leaves position control on and sets the target closed where the valve stays fitted, as BMW and some Mercedes prefer), and, because EGR cooling is gone, checks that the intake temperature model still makes sense. On EDC16 that’s forty or so parameters; on EDC17C46 more than a hundred entries across maps and the diagnostic table.

Limp mode after a delete

Limp comes from the reaction attached to a DTC, not the DTC itself. P2002 alone rarely limps. P2458 plus P244A on EDC17 does, because the ECU’s regen inhibit escalates to a torque limit. P0401 on most EDC16 doesn’t limp, on EDC17C46 it can after a few cycles. So the same list of codes limps one car and not another. Reset the soot and ash counters after flashing (VCDS adaptation on VAG, Xentry on Mercedes, Multiecuscan or a good scanner on Opel and Fiat), clear codes, and do one full drive cycle before you judge the file.

Examples of complete solutions

These are finished files with the sensor handling included: HYUNDAI TUCSON EDC16C39 0281015443 1037395837 DPF EGR OFF DUMP, OPEL VECTRA C EDC16C9 0281011616 55189631UK 1037372739 DPF EGR OFF DUMP, OPEL VECTRA C EDC16C9 0281013409 1037383690 DPF EGR OFF DUMP, MERCEDES VITO EDC16C2 0281012824 A6461500178 1037376864 DPF EGR FLAP STAGE1 TUNED, RENAULT FLUENCE DCM3.4 3039313452 3235393052 DPF EGR STAGE1 TUNED, AUDI A6 EDC16CP34 4F9997401C 0001 10SW087675 DPF EGR TUNED VMAX, PEUGEOT 807 EDC15C2 0281011133 1037364400 DPF OFF DUMP and CITROEN C8 EDC15C2 0281011334 1037368584 DPF OFF DUMP. If the software number on your label matches, the file fits; if not, we build from your read.

What to do with the sensors

Leave the differential pressure sensor fitted and plugged with both hoses on, and leave the temperature sensors in the pipe; the file handles their evaluation, and a plugged-in sensor never throws a circuit code. Unplug only if the file was written for that. The EGR valve stays connected on BMW, Mercedes and most EDC17 cars; on EDC15 and EDC16 VAG it can be removed.

Legal caveat, again

DPF and EGR removal is illegal for road use in the EU. Inspection in Germany, the Netherlands, Belgium and the UK now includes a visual check for the filter and a particle count or smoke test, and a gutted can fails the particle count. These files are for export, off-road and competition vehicles.

Send the full read, the tester’s code list and a photo of what’s been removed to the request form and we’ll say whether the existing solution fits or whether it needs building. Ready files are under DPF off and EGR off; the guide on OBD, bench and boot covers how to read the EDC17 units that won’t go by OBD.