EGR valve Volkswagen Golf IV and fault code P0401 (16786)
EGR valve Volkswagen Golf IV and fault code P0401 (16786)

EGR valve Volkswagen Golf IV and fault code P0401 (16786)

Old Volkswagen Golf 4 generations were going to 2006. They set about a dozen different engines with a good set of gearboxes. In particular, 16-valve motors 1.4 and 1.6 liters of different series show themselves as reliable and hardy aggregates with small problems. One of them is a broken or worn EGR valve that causes an fault code Р0401 (16786).

What is P0401 on Golf 4


The fault code Р0401 read by the OBDII scanner corresponds to the internal system fault code of 16786. These data directly indicate issues with the system of recirculation of exhaust gases. The fault code is not so critical to immediately muffle the engine, but it is necessary to eliminate it as soon as possible.

ошибка гольф 4

There are a number of related fault codes and fault codes:

  • Р0401 (16786) – Increased bandwidth of valve;
  • 17559 – poor proportion of fuel-air work mix;
  • Р0402 – EGR valve does not respond to requests;
  • Р0403 (16787) – crashing in the work of the valve;
  • Р0407 (16791) – Low signal level from EGR valve sensor.

The effects of tightening with the elimination of reasons that caused the appearance of an fault code P0401 Volkswagen Golf IV – a high fuel consumption, a possible print of the bottom of the piston, damage to the catalyst and valve damage.

So joking with the EGR valve is dangerous.

EGR valve on Volkswagen Golf IV. What is it and how it works


Theoretically, the recirculation of exhaust gases serves to reduce the amount of harmful nitrogen oxide on the exhaust only. The substance forms in the combustion chamber when the temperature of ignition exceeds 1390 degrees with the pressure remains very high.

But not everything is so easy. If the temperature in the combustion chamber is too high (for various reasons) there is a danger of detonation, a prayer of valves and pistons, there are a number of other negative phenomena. Therefore, since the early 70s, engineers began to take measures to reduce the temperature in the combustion chamber.

One of the most effective methods for this, there was a mixing to a working mixture of non-combustible inert gas in a small proportion, no more than 5-10%, sometimes up to 18%.

As a result, the simplest and cheapest use for this conventional exhaust gases. In all modern engines, the scheme of return (recirculation) of exhaust gases into the combustion chamber is realizing. It is important to adhere to the proportions that controls the electronics.

What is the EGR system Volkswagen Golf


The entire system is named EGR (exhaust gas recirculation), and the main dispenser of the exhaust on the intake is the valve. On cars Volkswagen Golf 4 generation with gasoline engines 1.4 and 1.6 liters (AFK, APE, BCA, ATN, may be other letter designations) EGR valve installed.

клапан EGR Volkswagen Golf IV

On older gasoline engines, for example, AHW, the valve looks different.

клапан EGR Volkswagen Golf IV

However, the principle of the system does not differ depending on the design of the valve. The main task is to submit a small amount of exhaust gases to administer in certain operating modes:

  • On the idle turns, the system is not used, the valve is closed since the exhaust contains a minimum of nitrogen oxide;
  • On maximum turns, the system also disables, because in the engine other priorities are maximum power;
  • The main range of the EGR system is the average turnover and the average load, speed from 60 to 100 km/h.

In modern engines, all this is controlled by electronics, which gives the impulse to the EGR Volkswagen Golf IV electromagnetic valve.

What are EGR valves


On the Motors VW mid 90s were installed pneumatic mechanical valves EGR. They corresponded to the maximum of Euro-2 norms. They worked simply – in the valve case, a shut-off cone associated with a loaded-loaded membrane was installed. In the upper part of the membrane, a discharge was created due to the pressure drop in the intake collector.

egr golf 4
The EGR valve Volkswagen Golf IV Vacuum-Mechanical Type Works on the following scheme.

As a result, the shut-off cone rose. The stronger there was a discharge, the higher the locking cone rose, and the more exhaust gases fell to the input. Of course, such a design could not provide the precision of gas dosing and could not take into account all modes of engine operation.

On the Golf Engines 4 after 2000 began to install EGR electromagnetic valves. Such a device dosage gases extremely precisely because it was guided using an electronic engine control unit.

клапан EGR Volkswagen Golf IV

How the EGR Volkswagen Golf IV valve works, the principle of operation


The VW Motor EGR Valve 1.4, 1.6, 1.8 and 2.0 liters have equipped with a not vacuum, but an electric drive of a shut-off cone. For this, the solenoid corresponded to the voltage from 3.2 to 5, depending on the load of the engine, operating conditions, temperature, pressure on the inlet, the position of the throttle valve.

Principal scheme of the EGR system on Golf 4

ECM collected data from all sensors and calculated the required degree of opening valve. Such valves, as in the photo, had only one tube ending with a filter to communicate with an atmosphere. As before, the EGR valve installs near the exhaust collector on the right, but is driven by an impulse from the engine control unit.

In the enclosure of the valve, a potentiometer (sensor), which measures the degree of opening a shut-off cone, and transmits these data to the ECM.

As a result of the operation of the supply of exhaust gases to an input during the heat heating (to the temperature of antifreeze 35-40 degrees), on the idle rotation of the engine and full capacity are blocked.

If contacts of the EGR valve do not supply voltage, it is completely closed. When the antifreeze is warms up to 35 degrees, the ECM provides a minimum voltage to the solenoid contacts that opens the valve. The degree of opening of the valve depends on a number of parameters:

  • load on the engine;
  • the number of revolutions;
  • antifreeze temperatures;
  • the air pressure on the inlet.

EGR valve sensor (Potentiometer) is located at the top of the node next to the contact group. Solenoid is a step electric motor, it is he by the team of EBU opens or closes the conical valve.

egr valve golf
Electronic EGR Valve Single stage (linear)

To keep the pressure inside the EGR valve stable, there is an atmospheric connection in the housing, on which the tube is placed. In some versions of 1.4 and 1.6 liter engines, the tube is output to the air filter, in most – at the end of the tube has its own filter, then the tube is not connected anywhere.

клапан егр гольф 4
A filter installs at the end of the atmospheric communication tube.

How to check the EGR valve on a Volkswagen Golf 4


To remove the EGR valve on the Golf is quite simple – just unscrew the two nuts on the valve body (in some cases two bolts), unscrew the flange of the communication tube with the intake manifold, remove the electrical connector, then carefully separate the valve body from the cylinder head.

egr golf


As we already know, data on valve opening, maximum operating stroke and zero point offset are stored in the memory of the ECU, which will be indicated by the corresponding fault code codes.

So, first check the performance of the solenoid. Measure the resistance at terminals 1 and 2. This is the solenoid winding. Rated resistance – 9 Ohms.

клапан егр гольф 4

Then check the resistance at pins 3 and 4 in the photo. This is a valve position sensor (potentiometer). In the off state, the resistance should be 1.7 kО.

сопротивление датчика егр гольф 4
Measuring the resistance of the EGR valve sensor with a multimeter.

If these data coincide with the nominal ones, check the stroke of the valve stem. This will require a power supply with smooth regulation of the output voltage by 12 V. Connect the contacts of the power supply to the power contacts of the solenoid and gradually increase the current from 3 to 5 V. At this time, the exhaust should be blocked from fully open to closed. What will it say about the working condition of the valve.

клапан егр гольф 4
As the voltage at the power supply terminals of the solenoid increases, the exhaust window must completely overlap.

If this is not the case, you will have to either disassemble the EGR valve or buy a new one. Theoretically, the valve is non-detachable, but in the lower part of the housing there is a roll, which can be gently loosened and gain access to both the potentiometer (EGR valve sensor) and the solenoid and valve stem.

In some cases, it helps to clean the valve channels from scale and deposits. To do this, use aerosol carb cleaners or the extreme end of the WD-40.

If you managed to repair, lubricate, clean the EGR valve mechanism, the place of flaring is carefully rolled, after which it is desirable to put it on a strong heat-resistant adhesive (two-component epoxy works well).

Which EGR valve for Volkswagen Golf IV 1.4 and 1.6 liters is better


If the repair fails, or the inspection showed a complete failure of the valve, you will have to buy a new one. It is new, not from disassembly, because it is unknown in what condition.

клапан егр гольф 4

The original EGR VAG valve for 1.4 and 1.6-liter engines has the catalog number 036131503T, the price is about $65-70 for a used one, and for a new one they ask from $215. Not cheap, but reliable. The life of the new valve is at least 300,000 km. Two gaskets are included with the original valve.

There are analogues. Example:

  • AND, №3813045, $38;
  • Mobiletrone, EVEU022, $65;
  • Pierburg, 728248170;
  • JP Group, №1119902200, $40;
  • Trucktec, 0714040, $70;
  • Engitech, №ENT500016.

Is it worth shutting down the EGR valve Volkswagen Golf IV


Based on the sky-high price of the EGR valve for a car from twenty years ago, many people solve the problem with a broken valve radically – just shut it down. In part, this makes some sense, but in the case of the vacuum-mechanical valve.

When the solenoid valve dies, the situation with its removal is complicated by this. All settings of the engine control system, all nominal parameters of the system, all sensors and their calibration designs to mix the exhaust to the working mixture.

заглушки егр
Here are the plugs with gaskets sold to remove the EGR valve on the Golf 4. Metal plug through the gasket is simply installs on the cylinder head.

Therefore, removing the valve without reflashing the electronic engine control unit can cause a lot of trouble.

The following manifestations are quite probable:

  • high fuel consumption;
  • unstable operation in transient modes;
  • overclocking failures;
  • engine tripping and a number of other consequences.

Therefore, if possible, it is better to install a working (new) EGR valve or qualitatively restore the old one.

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