EGR Off — disabling exhaust gas recirculation in the ECU

EGR Off disables exhaust gas recirculation in the ECU software. The EGR valve stays shut, and the ECU stops using it for air control and stops monitoring flow, valve position and the cooler, so EGR faults and the limits that come with them go away. The option is available for diesel ECUs and for petrol ECUs where the engine has an external EGR valve. The finished file with corrected checksums arrives on average in 30–60 minutes.

Why an engine has EGR

EGR feeds part of the exhaust back into the intake. Exhaust gas is low in oxygen, so peak combustion temperature and pressure drop, and less nitrogen oxide (NOx) forms. That is how VW explains it in its training material for the 2.0 TDI. The limits are tight: Euro 5 allows a diesel car 180 mg of NOx per kilometre, Euro 6 allows 80 mg.

The price is soot. The more exhaust in the charge, the less oxygen, and the more particulates, carbon monoxide and hydrocarbons. VW, for example, shuts the EGR when the temperature sensor before the turbo fails, and its training material says plainly why: to cut soot emissions.

How diesel EGR is built

The classic layout is high-pressure EGR. Gas is taken from the exhaust manifold before the turbo, cooled in the EGR cooler and fed through the valve into the intake after the throttle. Early engines used vacuum valves, later ones electric valves with a position sensor. The cooler can be switchable: on the VW 2.0 TDI, until the coolant reaches 50 °C the gas bypasses the cooler so the engine and the catalyst warm up faster.

Some Euro 5 and Euro 6 engines add low-pressure EGR: gas is taken after the particulate filter, already cleaned, and fed in before the turbo compressor. The VW EA288 and the Mercedes OM651 are examples. On some systems the flow in this loop is controlled with a separate differential pressure sensor.

How much gas to recirculate is set by maps in the ECU: engine speed, injected quantity, air mass, air temperature and pressure. The air flow meter (MAF) measures the fresh air: the more exhaust goes into the intake, the less air it sees. What changes when the MAF itself is faulty or removed is covered on the MAF Off page. If the flow comes out lower or higher than expected, the ECU stores P0401 or P0402. When the turbo cannot create enough pressure difference, some engines partly close the intake throttle to drive the EGR flow.

Why EGR systems fail

• Carbon. Soot from the EGR mixes with oil mist from the crankcase breather, and sticky deposits build up in the intake manifold, on the swirl flaps and on the valves. The EGR valve stops closing or opening fully.
• Short trips and cold weather. On a cold engine, deposits in the EGR system build up faster.
• The cooler. It heats up and cools down all the time, and sooner or later it starts leaking coolant.
• Electrics. The valve actuator, the position sensor or the wiring fails, and the ECU stores a circuit fault.

A valve stuck shut sets P0401: warning light, loss of power, rough running. A valve stuck open lets too much exhaust into the intake, and the engine may smoke and idle unevenly. On some ECUs an EGR fault also brings a boost limit. On the VW T5 2.0 TDI with a Delphi DCM6.2, for example, the EGR and turbo flow models are linked, and an open circuit on the EGR valve puts the turbo into limp mode.

EGR on petrol engines

Not every petrol engine has external EGR, and on petrol it does a different job. At part load the exhaust takes up part of the charge, the throttle opens wider, pumping losses fall, and the engine burns less fuel. On direct-injection engines running lean, EGR also cuts NOx.

So on a petrol engine we first check whether it has an external EGR valve and what the software does with it. If the external EGR was fitted for economy, part-load fuel consumption may rise slightly once it is off.

EGR fault codes

The basic codes per SAE J2012, with VAG wording. Manufacturers add their own codes for the valve position sensor, the cooler and the bypass.

What changes in the software

Blanking off the valve without a file does not work. The ECU keeps opening it, sees no change in air mass and stores P0401. An unplugged valve sets a P0403 circuit fault. So EGR Off changes the logic in the file itself.

What changes in how the engine runs. NOx goes up, that is the direct result. On a car with AdBlue, fluid consumption rises, because the ECU doses it by NOx. Soot goes down, and the intake stops collecting carbon from the EGR. Oil mist from the crankcase breather still reaches the intake as before.

Flaps Off (intake flaps), TVA Off (diesel throttle valve), DPF Off and Stage 1 are often ordered in the same file. If the engine has a low-pressure loop and the particulate filter is being removed, do EGR Off together with DPF Off: without the filter, unfiltered exhaust would go through the turbo compressor.

Blanking plate, connector and intake cleaning

• A blanking plate is needed when the valve is coked up and does not seal. A healthy valve is simply held shut by the file.
• The valve connector can be unplugged on some ECUs and must stay plugged in on others, or a circuit fault appears. Mention it in the order and we will advise for your ECU.
• A leaking cooler cannot be fixed in software. It is replaced or taken out of the cooling circuit.
• Old carbon in the intake and on the flaps stays where it is. If the engine has already lost pull, the intake needs cleaning.
• After flashing, clear faults in all modules and reset the adaptations: on some ECUs counters of old faults would otherwise mature on the first drive.

How to order the file

1. Read the original file via OBD or on the bench with the tool you use. We need an unmodified stock file.
2. Upload it to the portal and select EGR OFF. You can add DPF OFF, FLAPS OFF or Stage 1 at the same time.
3. Get the finished file with recalculated checksums, on average within 30–60 minutes.
4. Flash the file, clear the faults, reset the adaptations and check the car on a drive.

If your ECU is not in the list below, send the file with a request and we will check whether there is a solution. Keep the original: it takes everything back to stock.

Disabling EGR increases NOx emissions and changes the vehicle's emissions class. In the EU, the UK, the US and a number of other countries this is prohibited on public roads and may cause an inspection failure. The service is intended for tuners and is used where the law allows it: motorsport, off-road, export, vehicles not used on public roads. Responsibility for using the file lies with the vehicle owner.