Thursday, June 23, 2016

WHAT IS A VW EPC WARNING LIGHT

What Is a VW EPC Warning Light

The EPC warning light is an instrument cluster based LED found on all Volkswagen, Audi, Seat and Skoda vehicles fitted with a drive-by-wire system and EPC stands for Electronic Power Control. However the EPC warning light is not exclusive to these VAG cars, most other motor manufacturers also have them, since it's legislated to be part of the OBDII system. This EPC light when lit displays the letters EPC and primarily warns the driver that there is problems in the engine's torque system - (acceleration system). The reason why the EPC turns on, problem could be many, among which are the vehicle's knock sensors, its throttle system, its cruise control, its mass air flow system, its engine speed verification system or any of the other associated systems that cooperate in the drive-by-wire schema. 

When this EPC light comes on, the vehicle’s throttle valve (butterfly) may be limited in order to protect the engine from damage. It prevents the engine from revving above 2000rpm. This is known as limp mode and the ECU permits just sufficient power to drive the vehicle to a service center for repairs. To remedy the problem, the vehicle’s ECU should be scanned with an automotive diagnostic too, in order to extract the DTC's related to the torque problem.  Cars with an accelerator cable are also fitted with an EPC light but the ECU software is quite different, yet the overall principal remains the same.

All Volkswagen (VAG) vehicles have a whole array of dashboard warning lights in their instrument panels, specifically designed to alert the driver to any vehicle malfunctions or problems. In fact so does all most modern day automobiles. Having said that, it is only a matter of time before these lights start lighting up. Invariably and inevitably all cars will breakdown at sometime or the other but its nice to be warned about a mechanical problem before it actually occurs. For example, having a low coolant level light or an low engine oil-level light flash at you, accompanied by an audio alert is a blessing because complete loss of either coolant or engine oil could result in a very expensive repair. 

The one warning light that puzzles most drivers is the VW EPC warning light. Driver often ask, what is the VW EPC warning light? Like I've mentioned above, it is a bright yellow dashboard light with the letters EPC inscribed in bold.it  When lights-up to draws your attaention to a potential malfunction in the EPC system. When it lights up whilst driving and the trouble is related to a safety issue, the car will more than likely go into limp mode. This may sound quite serious but in most cases it's not. There are several reasons why EPC Dashboard Warning Light turns on, but through a process of elimination the cause can be tracked down fairly easily. 

The Engine Speed Sensor is  known to cause the EPC light to turn on. The engine speed sensor is a proximity magnetic transducer counting the revolutions of the flywheel / crankshaft and sends a steady stream of pulses to the ECU. So when this stream of data is interrupted for whatsoever reason for only a fraction of a second, the ECU  detects this and turns on the EPC light and cuts power to the engine. It does this to protect the engine from damage. 

If you have a scan tool, check for DTC errors. The following error code, 17745 /P1337, 17746 / P1338, 17747 / P1339 and 17748 / P1340 are the troubles codes that provides a  tell tail sign that the engine speed sensor is either loose or faulty, hence the car's engine cuts-out whilst driving and the speedometer is inoperative.  But in some cases the engine will start again. When this symptoms repeats itself often, you should know it is time to replace that pesky engine speed sensor.

The Accelerator Pedal itself is often the main culprit that causes EPC problems. A telltale sign is that the engine idles a lot faster than it aught to. To verify this, physical pull the accelerator pedal away from the floor board while the car is idling. If it reduces the engine's revs back to normal, then it is time to replace it, because the potentiometers that's built into the the accelerator pedal, have gone faulty. Accelerator pedal problems are numerous and the following DTC, 16504 / P0120, 16505 / P0121, 16506 / P0122, 16507 / P0123, 18038 / P1630, 18039 / P1631, 18040 / P1632, 18041 / P1633, 18042 / P1634, are linked to accelerator pedal errors. 

Mass air flow sensor is another engine component that can cause the EPC light to turn on. Cleaning the  mass air flow sensor with compressed air does often solve the problem but if the issue persists, its time to replace mass air flow sensor. But before changing it, check to see if any of the rubber hoses in its vicinity isn't perished. An leak in Air Intake System wil allowing air unmonitored to enter the intake which will throw a P2279 / 15093 error or a P0068 / 15101 error.


The Throttle body is by far the most common cause of an EPC problem though in many cases it is not the throttle body that's at fault but rather that it the needs to be recalibrated (adaptation). The scan codes like P2135 / P2136 / P2137 / P2138 / P2139  and P2140, will give a  good idea as to whether or not the throttle body require replacement.  But in many cases it turns out to be  wiring harness issue. The plugs that connects the throttle drive motor and the throttle position sensors is fairly troublesome ad should be checked before throttle is replace.

The Brake light switch can also cause the EPC light to come on because the torque control circuit uses the brake light signal as a ECU input signal when the car decelerates.  

The Injectors and the Ignition Coils can also cause the EPC light to turn on. I've heard that an incorrect spark gap on the plugs can also cause an EPC problem but haven't experienced it yet.  Driving with very little gasoline in the tank can also cause the EPC light to turn on because the high pressure fuel pump may lose pressure which then notifies the ECU to inhibit the torque circuit and switch on the EPC light and make the car go into limp mode.

I've experienced the Knock Sensor turn on the EPC light. Spirited driving also turns on the EPC light.

So as you can see there are several things that can cause an EPC fault.  This is not a complete list of EPC problems but as new ones are identified, I will post them.  The following questions prompted me to write a synopsis of what an EPC light is!

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What is an EPC light? What is an EPC warning light? What is an EPC light on Volkswagen? What Is the VW EPC Warning Light? What is the EPC light on a Volkswagen Jetta? What is EPC on a Volkswagen? What does it mean if the EPC warning light comes on in a Volkswagen? Volkswagen - EPC Warning Light, What does an EPC light on the dash of a Polo match car mean? EPC light came on and lost all power. 

The EPC warning symbol came on today while driving. EPC Light and stalling. EPC light came on and can't start the engine. EPC light on, what does it mean ? EPC light and engine check light. EPC warning light. Epc light. EPC + power loss/no boost.  Do not exceed 4000 rpm  EPC light.   EPC error where the car shakes terribly.  ESP EPC & Engine Light ON.  EPC Light and Stalling. Polo bluemotion 58 plate and a yellow engine light came on. I read the manual but still not sure something to do with the exhaust??

A little help as my wife needs the car for work.2002 1.6L GOLF, EPC light on. POWER LOSS An EPC light will appear on the dash randomly whilst driving. Once it is on, there is a noticeable loss in power and it stays this way until the... volkswagon polo epc warning.step by step guide to turn light off please, preferably without visiting expensive vw garage. Have diagnostic computer to see code! EPC light came on and engine will not rev higher. I have a vw polo and the EPC warning light has come on what should i do? Orange light 03 vw polo. VW Polo Map sensor fault code idling poorly. EPC light on my dashboard 2001 vw polo. It has something to do with the engine management, retarding the power of the engine.

18 comments:

  1. Just wondering would an ECU with some corrosion cause the Epc light to come on on a Jetta? Had the light come on and it limited the revs to 1000rpm. Turned the car on and off and it was fine again and has been the past few days. Brought it to the dealer today to get it checked out and they told me the ECU is corroded and is what caused the problem. They want €1400 to fix it but I'm not feeling too good about paying that especially since the problem doesn't seem to have resurfaced since the other day

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    1. Hi There!

      Corroded contacts on an ECU can cause the EOC light to come on, especially if the corroded contacts connect to the accelerator sensors / throtle body sensors / drive by wire circuit. However, if the car drives perfectly normal, the corrosion may not be so bad that it causes poor contact. Forking out €1400 on a dubious diagnosis is a lot of cash. If you into DIY, get some electrical contact cleaner and spray the corroded contacts, it will displace moisture, protect the contacts from further corrosion and reduce the resistance between the actual contacts. Best of Luck!!!

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  2. Hi there, am driving a Polo 1.4 2008 model, my car has recently started cutting power when I drive with the headlights on and the EPC sign is appearing on the dashboard when the lights are on. Please help me, what can be the problem and what do I need to do?

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  3. Hi Matimba

    Before the problem gets any worse, you need to have your car scanned at a mechanic that has VCDS. Once you tell me the fault codes, I can steer you in the right direction. But without that, its just a wild guess because it can be one of many things or a combination of them.

    Your question is like asking me "how long is a piece of string"? What I suggest though, is for you to read through some of my previous blogs, perhaps something may sound familiar, then you can do the necessary. Cheers!

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  4. Hi Faried, I hope ypu can help me.
    I drive a Seat Leon 1.4 TSI. I like to drive hard and I get the EPC light whenever I hit more than 5000 RPM.
    I have an air intake system but I have had this same problem even when I had a replace filter only.
    The vcds reads air intake leak, but fisically everything is fine, could this epc light come just because there is more air entering the engine? If so, this is shit, haha.

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    1. Hi Monasterix

      It sounds like your problem is related to stoichiometrics. The “perfect” fuel air mix is called the “stoichiometric fuel ratio” and dictates that both the fuel and the oxygen in the air are completely consumed during combustion. Theoretically this mixture equates to 14.7 parts of air to 1 part of fuel however from a practical standpoint most modern fuel mixtures burn closer to 15:1 than 14.7:1.

      Your TSI's ECU gets feedback from its O2 sensors / catalytic converter whether the mixture was too lean or too rich and adjusts your fuel trim to keep the mixture at stoichiometric in order to maintain engine power. Too much air causes a leaner mixture, too little air causes a richer mixture. Hard acceleration / high boost also causes a rich mixture, making the engine prone to detonation.

      If you have an air leak in one of the rubber hoses or perhaps a loose hose clamp in the vicinity of the Mass air flow sensor the mixture will be skewed and if the ECU cannot compensate for it, because it's out of the ECU's range of preset values, then it is bound to pop the EPC light and Check Engine Light followed by limp mode. Also if your knock sensors detect excessive detonation, it will also trigger an EPC and limp mode to save the engine from damage. The ECU preset values can be altered with VCDS more towards your style of driving but that's a job best left to the professional tweekers.

      Cheers!

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    2. Thank you very much Faried, I'll see what works for me.

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  5. Epc light on a 2006 Jetta with a car with swivel lines for tracktion symbol on dashboard also. What this means?

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    Replies
    1. Your car is fitted with a traction control system (TCS) which helps to reduce tyre slippage on slippery surfaces during acceleration. Since your TCS warning light is on, it means that you're not getting any assistance from the Traction Control system. So you need to have it checked.
      The EPC light triggered due to the TCS isn't working in the sense that TCS is torque related.

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  6. Epc light on a 2006 Jetta with a car with swivel lines for tracktion symbol on dashboard also. What this means?

    ReplyDelete
    Replies
    1. Hello there!

      Your car is fitted with a traction control system (TCS) which helps to reduce tyre slippage on slippery surfaces during acceleration. Since your TCS warning light is on, it means that you're not getting any assistance from the Traction Control system. So you need to have it checked.
      The EPC light triggered due to the TCS isn't working in the sense that TCS is torque related.

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  7. I have a 2013 VW Jetta sportwagon. Last summer it would stall when slowing down or idling and the battery sign would come on. Mechanic did a throttle body relearn and gave it back. Seemed to be ok for a bit. Then started up again- took it back to mechanic but they never got it to die and returned it. It has been fine all year until this summer. Again, it turns off with the battery sign showing when slowing down (getting off highway) or idling (at stop signs and red lights). Today, I also got the EPC light and the battery light. I turn the car off and turn it back on and its fine. Any thoughts on what it could be?

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    1. Hi Marta

      The battery icon coming on, purely indicates that the engine switched off, so that's not a matter of concern but the engine stalling is and it seems to be intermittent. The mere fact that your mechanic did adaption and it seem to last a year makes me think that he may have moved, unplugged and replugged the wiring harness into the throttle body drive module. It's very likely that you have a pin or two in that plug that occasionally doesn't make good contact. When it looses contact the ECU detects this and turns on the EPC light. However by restarting the engine, it vibrates sufficiently to restore the contact, until the next time the plug/ pin breaks contact. Have your mechanic lubricate the plugs of EPC circuit with electrical contact spray. It may solve you problem, it doesn't let him replace that plug.

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  8. Can a broken fuse cause the epc light to come on?? It's just come on today and found a broken fuse it's off but may come on... :-/

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    1. Hello there!

      Yes, of course a blown fuse can cause the EPC light to come. There are several ancilliary circuits that sends signals to the ECU that controls the EPC circuit. If one of these signal are missing, the EPC light will certainly illuminate.

      For example, On the Audi S8 if fuse #5 is blown the Engine Management doesn't work and causes the EPC light to come on. Another example is when the fuse to brake lights of a Polo is blown, the EPC light come on, because cruise control cancellation signal is taken from the brake supply line.

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  9. Any idea why the EPC light turned on in a 2003 Polo? Everything is working as normal. Accelerates fine, goes over 2000rpm, brakes light work, etc. Nothing different while driving. It just came on suddenly.

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  10. Epc light on car refuse to start its polo tsi 1.4 2017 model

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