DRIVE BY WIRE

VW - DRIVE BY WIRE (Drive-by-Wire)

If you arrived on the VW Polo website because you searched for  Drive by Wire (DBW), EPC, or EPC light or engine won't rev, Steer-by-Wire, or limp mode,  then you have certainly arrived at the right place. There are several definitions for ECP, the first of which will be explained, is Electronic Parts Catalog (EPC).

EPC stands for Electronic Parts Catalogue (EPC) and all Audi, Volkswagen,  Skoda and SEAT parts are listed in ETKA V7.2 EPC (Electronic Parts Catalogue). This catalogue is purchasable online and downloadable but the file is huge. Companies like Mercedes Benz, Toyota,  Enigma, Attrakt among many, many others host computer based electronic catalogs of the individual auto parts and accessories that make up their engines, cars, tractors, specialized machinery and farming equipment etc. Restated, an EPC is a catalogue in electronic format much like CVS data or a database file or similar, that can be downloaded or is accessible online.

Then there is the second type of EPC - Electronic Parts Catalog (EPC) software. MultiCat and Msys.EPC are companies that specialize in the software that can display an exploded view of an assembled device. For example, the exploded view of an engine, or gearbox, or cylinder head, showing the individual bolts and nuts, flanges, hoses and brackets, etc. and their component part numbers.

Thirdly, there is also the Electronics Parts Catalog (EPC) which is an electronic list or database of semiconductor components, from diodes to transistors to integrated circuits to thyristors, etc... This EPC is often called and equivalents book or catalog and hosts the specifications of semiconductors from several manufacturers. A typical EPC is the RS Electronic Components and Tools Database. This EPC doubles up as the third type of EPC which is the Electronic Product Code. Component Product Codes look like,  1N4148 or BC337, MCP2515, TYN812RG, etc... for electronic components.

However, there are many more EPC definitions, some of them can be found at the end of this blog. I could explain all of them individually but none has any relevance to the subject at hand, viz EPC - Drive by Wire. Drive-by-Wire also know as  DbW, Steer-by-Wire "x-by-wire" or simply "by-wire".

DRIVE BY WIRE

And finally, the Electronic Power Control (EPC) that freaks out almost each and every VW 1.6 Polo, Audi TT, Skoda, SEAT and  Golf TDI, owner. Most vehicles with Drive by Wire [Drive-by-Wire (throttle control)] usually have a Electronic Power Control (EPC) indicator lights on its dashboard which lights up when  there's a problem with the Drive-by-Wire system. This would involve the two accelerator pedal sensors G79 and G185 and in some cases the two sensors G187, G188 inside throttle control valve body - control actuator. [As discussed in my previous blogs] When the engine idles, neither the Throttle Valve Angle Sensor nor the Accelerator Pedal Position Sensor are monitored for faults by the ECU, as such, the engine does not respond to accelerator input but will limit engine to 1200 RPM.

The  basic components that constitute the Electronic Power Control (EPC) circuit. 

There is no throttle cable involved, because its an electronic throttle control.

The Electronic Power Control (EPC) circuitry consists of EPC light, Accelerator Pedal, Throttle Control Valve,  DBW  (no throttle cable,) Injectors and the Engine Control Unit (ECU). Have a look at the diagram above. The inputs to the ECU is marked green and the outputs from the ECU is marked blue.  Check that the brake light bulbs are OK, if not check the brake fuses. There are other inputs to the ECU from numerous other sensors or units for example the Automatic Gearbox Control unit, Cruise control unit, Air conditioning unit, Lambda Regulation unit, Knock Sensor units, Alternator, Engine Speed Sensor unit, ABS and the  Power-assisted steering unit to mention but  a few. 

The CAN-Bus bidirectional connection is marked in orange. Some of the other inputs like Knock sensors and Lambda regulator and Engine Speed Sensor unit can also cause the EPC light to come on. If the Engine Speed Sensor unit is responsible, it will reset itself after a while and if the Lambda regulation is faulty the vehicle will smoke and turn on both MIL and EPC lights, but if the Drive-by-Wire - DBW (not drive by cable) system is faulty then only the EPC light will be on.

Both the accelerator sensors and the throttle valve sensors work on the same principle since all 4 of them are potentiometers. The input voltage is 5 Volts and the increments are in millivolts implying that there is an  acceleration range of between 0 and 5000.  Throttle valve angle  sensor 1 and Throttle valve angle sensor 2, Accelerator position sensor 1 and Accelerator position sensor 2 sliders makes contact with the resistive track and outputs the appropriate voltage level to the ECU. These resistive tracks are prone to go faulty since they are gold plated contacts running on gold plated copper tracks etched on a PCB. Over time the contacts wears right through the gold and copper plating, only making contact with the bakelite or fibreglass substrate. This type of potentiometers are less reliable than ceramic thick-film potentiometers.

When the EPC warning light goes on and your acceleration goes limp and the engine won't rev-up there is an easy cure but there may be exceptions. Get the car home even if it means driving really slowly in "Limp Mode". Once home, disconnect the battery for about 15 minutes or so, but not more than 20 minutes then reconnect. NB! do not disconnect the Live terminal, disconnect the Earth terminal. If the battery is disconnected for more than 20 mins you will lose your radio settings since the radio also participates in volatile and non-volatile memory of  the CAN-Bus. 

Reconnect the battery but make certain that the ignition is off. Once this is done, turn on the ignition so that the dashboard lights go on but do not start your car and DO NOT touch your accelerator pedal. After about 5 minutes the throttle body will aligns itself. After 10 minutes turn off the ignition, wait for 2 mins then start the car and let it idle for abut 2 minutes as well. By now, the EPC warning light should be off and the engine will rev as normal.You may have to to this twice. If this worked for you, please do give me some feedback with a comment.

VW Airbag diagnostics 

VW Instruments - Immobilizer

   

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COME MORE EPC DEFINITIONS

EPC - Engineering, Procurement & Contracting, 

EPC - Engineering, Plant  Construction,

EPC - European Paralympic Committee,

EPC - Electronic Product Code, 

EPC - Event Promotional Council,

EPC - Energy Performance Certificate,

EPC - Engineering, Procurement and Construction, 

EPC - Event-driven Process Chain, 

EPC - Evolved Packet Core,

EPC - European Patent Convention,

EPC - Eastern Provincial Council, 

EPC - Electronic Poetry Center, 

EPC - European Policy Centre,

EPC - European Political Community, 

EPC - European Political Cooperation, 

EPC - Evangelical Presbyterian Church 

EPC - Export Promotion Council, 

EPC - Electricity Plant Controller, 

EPC - ElectroPlating Cathode,

EPC - European Payments Council,

EPC - Electronic Packet Collision,

EPC - Electrical Professionals Council,

Etc...,

EPC LIGHT

EPC LIGHT

A few months ago the battery in my VW Polo Classic remote key, gave up the ghost.  I used the remote key to lock the car and set the alarm / immobilizer the night before but it refused to open the doors the following morning. So I unlocked the car with the key.  That’s when I realized that my 2007 VW Polo Classic Highline only has one door lock and that I only had access via the driver’s side door.   Neither the left side passenger door nor the rear doors on either side have any locks keyholes. This didn't surprise me because cutting cost has become the new standard in new car design. By not fitting these legacy locks, the car manufacturer saves the cost of three locks, the internal door mechanisms and the labour cost to install them when the car is assembled.  Multiply this amount of savings by the entire vehicle production for the year and you can surely see their total saving.

The Battery inside the electronic key housing.

That brings me to another cost saver implemented in most cars manufactured during 1996 and later. If you heard about OBD II (On-Board Diagnostics II) and CAN-Bus (Controller Area Network-Bus), you will have some notion what I am talking about. With the implementation of CAN-Bus auto electric wiring has been reduced to a bare minimum.  The average older car had between 300 – 400 meters of wiring, used for its head lights, tail lights, windscreen wipers, horn, dashboard electrics, alarm system, central locking, interior lighting etc, etc ...  Much of this wiring are roughly the same thickness (0.5 - 1.5 mm square) to carry the required current to the various devices.  But inside the engine compartment there are numerous thicker wires for the starter, ignition, air conditioner fan motor, alternator, main supply to the fuse box as well as  earth straps to mention but a few.   All these copper wires range between 1.5mm square – 15mm square, some of which are tin plated to minimize corrosion. Not only is this 400 meters of copper wiring expensive, it also weights a good 60-70 kgs.

By embracing the CAN-Bus technology, manufacturers save on the purchase of about 50Kgs of copper wire. Fifty kilograms of copper wire multiplied by the annual car production gives you some idea of the overall saving. Fifty kilograms taken off the weight of a car also gives it a better 'power to weight ratio' hence making it more fuel efficient.  With CAN-Bus technology,  all the  control modules in the car are interconnected, on a serial data network, each module taking charge of a sub circuit of  the electrical system. These modules are network similar to USB (Universal Serial Bus) used in computer networking.

VW EPC LIGHT

However,  CAN-Bus and OBD II was not implemented to save copper, nor to lessen the weight of cars neither to make cars  more fuel efficient.  It was firstly agreed upon by the EPA, then legislated by several Governments whose countries manufacture cars, to install an EMS (Engine Management System) in every new car built after 1996. This management system would monitor the engine and transmission of the car and insure that 'engine emission levels' stayed within a predetermined margin of compliance.  If this level is exceeded due to engine malfunction, the embedded diagnostic system should be able to recognize it and recorded such malfunction and also alert the driver with some form of MIL (Malfunction Indicator Light). Alternatively turn on the EPC light (Electronic Power Control - epc warning light) and stops the  car from revving up or  inhibit the management system and shut the car down.  The frequency of engine misfires or malfunctions are recorded in code format (vw epc code) designed by the Society of Automotive Engineers (SAE) in the ECU's non-volatile memory which is only accessible by the service agents or by someone with a modern day ODB II / CAN-Bus compliant diagnostic scan appliance.

Anyway let me return to the story of the remote control battery. Off I went to the local VW agent to buy a replacement battery.  I drove  a good 40 Km there  and back but still returned without the battery. It was just way too expensive for a small mercury cell. Problem was, I didn't phone to find out how much it cost. At the price that this VW agent charged for the  fob key battery I could manufacture it myself and it would still be cheaper. So I scouted around at a few photographic shops for this particular battery and eventually found a pharmacy that sold them. Hypothetically, if I bought all the pharmacy’s battery stock and sold it to this VW agents at half their asking price I would in fact have made a very comfortable living.

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MANIFOLD

MANIFOLD / EXHAUST

It was about 2:30 a.m. when I returned from a long distance trip. I was tired but smiled to myself before I climbed into bed because my 2007 VW Polo Classic Highline really performed well and brought me home without incident. I was amazed, blown away in fact. 

After breakfast the following morning, I intended to go to Milnerton to see a client but when I started the VW Polo, I was greeted by  frighteningly loud noise. I smiled too soon. Immediately I switched off the engine. It actually sounded like the VW Polo had no manifold system fitted at all. For the record it wasn't like the sound of a broken silencer or a hole in the exhaust system. It literally sounded as if there wasn't any exhaust system at all.

My first thought was that someone must have liberated my exhaust system during the night whist I was asleep and sold it off as scrap metal. Theft in my locality has become quite rife and this is known to have happened. Radiators and batteries seem to be targeted more often.  However, on closer inspection I was relieved that the exhaust was still there. I started the VW Polo once more rolled underneath the front suspension and discovered hot air was blowing from a space  where the flange gasket is located. It was very awkward to get my hand in there and I was wondering what this repair was going to cost. A trip to "Mister Silencer" and three hundred and twenty bucks later the VW Polo was once again ready for the road. I expected one of the dashboard EPC warning lights to light-up or one of the CanBus interconnected computer modules to immobilize the car but its seems that the manifold exhaust  just runs much too hot to attach a sensor to it.

Anyway, in order to fix or fit a new flange gasket the complete knuckle had to be removed. They hoisted the car on a maintenance lift and inspected its underside for the origin of the noise. It came from above the flexible bend which looked like matted wire mesh. Essentially the joint between the manifold branch and the exhaust manifold had to be removed.  I was told the flexible mesh compensate for vibration, should the silencer knock against a pavement of something, it wouldn't brake off of get damaged because of its flexibility.

Just two days prior to this, a young women ran into my rear bumper with her sparkling new look Audi A8 whilst she was chatting on her cellphone. There was no physical damage to neither of the cars but thought that she was the cause that my exhaust had given trouble. According to the dude at "Mister Silencer", its highly unlikely because the impact from behind would not have pushed the exhaust towards the engine because of its flexibility. Oh well,  either way I had to pay for it. FYI my VW Polo had every service on time since new and currently has 88250 Km on the clock. Soon it will be going for its 90000 km service and my timing belt will be changed. I've been driving with the dreaded fear that it might snap in mid travel and bend all my valves in the process or even bust the tops of one or two pistons.

In my first blog I mentioned I simply love German engineering because when a German designed car snaps a timing belt, there is no mechanical damage to the engine. This is so unlike the Japanese, American, English and French designed cars, all of which bend valves, bend conrods, break pistons or knock holes through their cylinder block. Since my VW Polo Classic 2.0L Highline is soooo different from all the previous German cars I owned, I just have this feeling it was designed along the same money making monopolistic ideology of modern car design - the cash cow that  sells spare parts.

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VW POLO - EPC LIGHT

EPC LIGHT 

Yesterday my VW Polo just wouldn't start, the engine cranked, but sounded as if it didn't crank fast enough in order to start. A good few hundred bucks later for a new battery, she started just fine. I suppose after four years, one should expect a battery to give up the ghost.  I thought it was just peculiar that it died without any prior warning, without lazy cranking or dim headlights or a croaky hooter. Anyway, this morning when I started my VW Polo Highline she had some really serious issues. It just wouldn't rev-up. When I looked at the instrument panel, the amber EPC warning light  was lit-up yet she idled perfectly normal. The moment I accelerated there was no power, but could only rev to 1200 rpm, it kinda seemed like fuel starvation. 

Only when  I revved; it seemed like there just wasn't enough fuel available, it sort of smothered. The  Amber / yellow EPC light on the dashboard is normally on when I turn on the car's ignition, as can be seen below, but the moment she starts, the EPC warning light goes off, or resets the EPC light on a Polo, which was perfectly normal as far as was  concerned.

I experienced this yellow EPC light issue once before, or at least something very similar a few months ago. I was driving through Melkbos Strand with my VW Polo, traveling at about 100kmph. As I passed a high school where some dudes were playing  soccer. The very next thing I saw, was their soccer ball coming over the school fence, it hit the road, bounced a few times  and  rolled directly towards the front of the car. There was no way I was going to swerve to avoid striking the ball because the pavements were like really high and I didn't want to damage my magwheels. There was also an oncoming car approaching from the opposite direction, so I couldn't even cross lanes to avoid it,  I just had to go over the ball. By this time, I had already reduced my speed to about 40Kmph. Somehow the ball got jammed between the undercarriage (sump / front suspension) of the Polo and the road. Instead of it rolling, I could hear it chafing along the asphalt. Then the ball suddenly burst with a tremendously loud explosion.

Immediately the EPC light came on, and there was no power. The car just rolled forward until it came to a halt. My foot on the accelerator had no effect. I tried revving the engine but to no avail, it just wouldn't rev. So I switched it off. A few seconds later I started the car and it started just fine but the EPC light stayed on and now, it at least revved to 1200 RPM. I needed to get off the road or at least to the nearest filling station / garage workshop. So I drove very slowly and even when I tried to go faster the car just wasn't going to go faster that 10kpm, even with my foot flat on the accelerator. Eventually... I arrived at the filling station, switched off the engine and popped the bonnet. I saw my air conditioner condenser was hanging skew. The explosion of the ball  under the condenser broke the plastic lugs that was screwed to the body. The screws were still in the lugs but the condenser was hanging out below my front bumper. So I went and  bought some cable ties at the local supermarket and re-secured the condenser as a temporary measure.

I then restarted the car. The EPC light was still on, so I borrowed a spanner at the filling station and disconnected the battery. Since the Polo was all electronic, I figured it would be equivalent to a computer cold reboot when I reconnected. So, after a few moments I reconnected the battery and started the car. The EPC light was off and I could rev the car as normal. I was so chuffed because I could see myself driving home, all of  the 70km distance at 10kpm. When I concluded my business in Melkbos, I was on my way home, about 5km from Melbos Strand when suddenly the EPC light come on again, and once more there was no power. Even with the accelerator pushed-in all the way to the floor, I was still just getting 10kpm. I came to a halt, disconnected the battery for the second time then reconnected it after like 2 minutes, which seemed to have cleared the problem and the engine revved just fine.  For the rest of the day the Volkswagen Polo behaved.

The graphic below shows all the dashboard lights amongst which are the Trailer towing mode indicator light, the Electro-hydraulic power steering malfunctions light, the Fog-lights operation light, the Rear seat lock warning light, the Cruise control light, the Unauthorized key electronic immobilizer continuous flashing light.

What I came to discover later, is that there are 2 knock sensors placed at strategic positions in the engine block, 1 per 2 cylinders. So, any engine noise louder than the knock sensor's preset decibel level, will activate them. This in turn  triggers the Engine Control Module (ECU) which then cuts the power via ODB II  CAN Bus, thus saving the engine from further mechanical damage. However, in my case this wasn't engine trouble but rather an external factor with the same result. The knock sensor or sensors picked up the loud bang of the bursting ball and interpreted it as coming from the engine.  That's artificial intelligence for you. What I came to understand much later is that Knock sensor K1 caused the EPC light to come on whereas K2 causes the MIL to come on. If both your EPC and MIL is on it could be K1 and K2 related but this should be determined in conjunction with the DTC which can be read with a scan tool from the non-volatile memory of the ECU. My problem turned out to be the potentiometers on the accelerator pedal that was intermittent. I replaced the accelerator pedal and I've never seen that pesky EPC light again.

FURTHER READING

NB!
If you wish to understand how the knock sensor and the  EPC light circuits works, read some of my other pages like KNOCK SENSOR, DRIVE-by-WIRE, KNOCK SENSORS   EPC EXPLAINED and  EPC EXPOSED, EPC REVISITED or EPC DEMYSTIFIED PART 1, PART 2 and PART 3

VW Bluemotion on Tow,
Why the engine light comes on.

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