VW POLO CANBUS

If you own a Volkswagen Polo, you more likely that not already know that a Controller Area Network (CAN) bus is an automotive wire network loosely referred to as a bus. The word "bus" comes from the electrical power distribution sector where bus-bars were considered a metalic strip made of copper, brass or even aluminium that served as a source of electric power to the load. 

CAN BUS

However CAN Bus is more akin to Ethernet than a bus-bar. Ethernet is a computer networking technology using Unshielded Twisted Pair cable (UTP) either CAT5 or CAT6 which is now commonly used in local area networks capable of sending  IPv4 / IPV6 packet across its networks at speeds ranging from as slow as 10Mb/s to as fast as 1000 Gb/s, hardware dependent of course. 

Twister pair electrical wires with various colour tracers.

Likewise CAN is a network technology commonly used in automotive networks capable of sending CAN-frames across its network at various speeds, again application dependent. It is essentially a  very reliable multi-master arbitration free serial bus, connecting numerous Electronic Control Units (ECUs) aka nodes together.

CAN BUS vs ETHERNET

The big difference between the two, is that Ethernet is an 8-wire bus comprising of 4 unshielded twisted pairs of wire, each with a specific colour coding, whereas CAN has only a single unshielded twisted pair of wires also with a specific colour coding. The CAT5 protocol insists on 2 twists per centimeter and CAT6 with more twists per centimeter whereas the CAN protocol insists on a 1 turn per centimeter. The lay of these wires are very specific and necessary to reduce or cancel interfering signals picked up from the environment by them, which is more commonly referred to as "crosstalk".

CAN BUS HIGH & LOW

Bearing in mind CAN comes in two varieties used for different functions, viz CAN-High (CAN-H) and CAN-Low (CAN-L).  CAN-H is used for the Powertrain, the Convenience and Infotainment buses. 

Whereas CAN-L is used for the rest of the bus wiring.  Both CAN-High and CAN-Low uses different colour wires for different makes of vehicle. For example:-

Manufacturer        CAN High        CAN Low

Mercedes                  Brown/red         Brown

Volvo                        White                Green

Vauxhall                   Green                White 

BMW 1 & 3             Green/orange     Green 

BMW 5 & 6             Black                 Yellow 

Porsche                     Yellow              Black

The big difference between the three buses for VW,SEAT, Skoda and Audi is that:-

1) The Powertrain bus wires interconnected to all the powertrain modules / nodes are coded Orange & Black CAN-H 

2) The Convenience bus wires interconnected to all the convenience modules / nodes are coded Orange & Green CAN-H 

3) The Infotainment bus wires  interconnected  to the infotainment modules / nodes are coded Orange & Violet /Purple CAN-H 

4) CAN-L bus wires to all the interconnected convenience modules / nodes are coded Orange & Brown. (Electronics colour code 31)

REPAIRING WIRES

CAN wires are typically multi-strand 0.35mm to 0.5mm square with 120 ohm termination impedance, capable of transmitting information using two complementary signals which makes them even less prone to crosstalk. But thin wires are prone to break and if and when they do, it is recommended  that when repairing these CAN Bus wires, that both wires must always remain the same length and of equal thickness. 

Implying CAN BUS is extremely unforgiving. So, when wire 1 of the pair is broken, wire 2 should also be cut and the piece of wire added in-between must be exactly the same length; and that the lay length of 1 turn per centimeter must be observed. 

ELECTRICAL INTERFERENCE

Failure to do so, may created a discrepancy in the wire length of the one wire in the twisted pair as well as in their differential voltages, hence result in network errors — ground noise, electrical interference, hum, buzz,  spark plug spikes — cannot and will not be appropriately cancelled. 

Whenever repairs are made to any CAN Bus wiring, it is highly recommended that all CAN Bus wire repairs are covered and highlighted with yellow insulation tape to signify to anyone doing successive work, that a previous repair was carried out. 

That EPC light.

The most likely reason you're reading this blog post, is because you encountered an EPC fault with your Volkswagen vehicle. I bet you wondered what that yellow/orange light was when it lit-up or perhaps startled when you car went into "limp mode". Whether you're driving a VW Polo or VW Jetta, VW Golf,  VW Caddy, VW Passat, T-Cross, Sharan, Touareg, Transporter, or any other Volkswagen or even a German Audi, or a Czech Skoda or a Spanish VW SEAT, you've come to the right place because they all have an  Electronic Power Control circuit. 

In fact all "modern day" vehicles have EPC circuit, which loudly says that the automotive industry have finally reached some consensus on standardization. But let me tell you what the EPC light actually is. It's just a signal light informing you that there is an error in your vehicles torque circuit. That's the short answer, however, I can tell by the look on your face that it wasn't a  satisfactory answer, so let me give you the long version.

The EPC light is part of the Electronic Power Control Circuit which is just one of the components of OBD-II which was mandated by a certain regulatory bodies with regulatory intent. Their initial intention was to limit carbon emissions / exhaust fumes from cars on the street of America. 

The California Air Resources Board (CARB) and the Environmental Protection Agency (EPA) together with the Society of Automotive Engineers (SAE) and the International Organization for Standardization (ISO) collectively originated the On-Board Diagnostic (OBD) System because of high levels of smog produced by automobiles throughout the USA.  

Their initial On-Board Diagnostic System was subsequently superseded by the all new and improved verion OBD-II, hence all cars manufactured post 1996 has an Electronic Power Control Circuit and by extension an EPC light. The European on-board diagnostics (EOBD) regulations are the European equivalent of the American OBD-II. 

On-Board Diagnostic (OBD-II) is an automotive mechatronic, micro processor / micro controller based computer system with programmed presets that continuously monitors inputs from numerous sensors fitted through the car. 

It then computes/compares/ compensates these inputs against stored data and drives various actuators to perform certain tasks. In a nutshell OBD-II is an input/output (I/O) information processing system much like the PC / laptop / or even your smart phone. By example, a keyboard, a mouse, a joystick, a scanner and a microphone are common computer input devices whereas a HD monitor, a printer, speakers and headphones are common computer output devices. 

Here the computer/laptop makes calculations based on its internal operating system and software to do something intelligible for humans. However in the case of OBD-II, its CPU (Central Processing Unit) is called an ECU (Electronic Control Unit) and among its input sensors are the Accelerator Position Sensor, Mass Air Flow sensor (MAF), Lambda O2 Sensor, Knock sensor, Oli level sensor, Coolant Temperature Sensor, the Camshaft Position Sensor, the Crank Position Sensor, the Wheel Speed  Sensor etc, to mention but a few.

Among its output actuators and solenoids are the drive-by-wire electronic throttle actuator, the fuel injectors, the EPC light, Malfunction Indicator Light (MIL), the Immobilizer, the Airbags and the Power Steering Pump, etc, again to mention but a few,

This ECU is sometimes referred to as an Engine Control Unit especially when intending to make reference to the TCU (Transmission Control Unit). The ECU is sometimes even called ECM (Engine Control Module) when making reference to other electronic control modules like the ABS module, the Instruments module, the Central Electronics Module, the CAN gateway module, the Radio Module, etc, again to mention but a few 

However, the ECU and the TCU are collectively referred to as Powertrain Control Module (PCM). The ECM essentially controls the efficiency of the engine performance by using a Crankshaft Position Sensor to determine the position of the cams in order to activate the injection of fuel into the cylinders and the timing of the ignition spark to ignite it at precisely the correct moment in petrol engines. 

Likewise the ECM in Diesel engines, plays a huge role in the success of the turbodiesel models. But in order for this to happen, an electronic throttle control had to be introduced, replacing the  cable from the pedal to the carburetor system which was prone to idle speed deviation between a hot and cold engine that became more and more prevalent as the components wore out. 

In so doing, the ECM can adjust the electronic throttle angle during acceleration to achieve the right quantitative relationship ratio between the actual airflow through the engine and the injected fuel thus maintaining Stoichiometry. Controlling the throttle airflow on the fly, markedly improves overall torque and driveability which is known as torque-mapping, an advantage that is only possible with drive-by-wire. 

So, the Electronic Power Control Circuit consists of the ECM, the Accelerator Position Sensor, the Throttle Position Sensors, the Throttle Actuator, the MAF / Air Filter, the Fuel Injectors, the High Pressure Fuel Pump, Fuel Temperature Sensor, Fuel Rail Pressure Sensor and Pressure Relief Valve. 

The single accelerator position sensor is made up of two individual potentiometers each acting independently of the other but collectively operate with opposite polarity voltages supplied by the ECM, as a safety back-up for one another. 

Thus, if either potentiometer fails, the ECM will activate limp mode. This is a safety measure that prevents the system from acting as if it had an accelerator cable that got stuck in the runaway position and the makings of a potential accident. The cruise control also has influence on the throttle body and requires the brake pedal to be depressed to cancel the cruise control. 

The ECU normally takes this cancellation signal from the brake light MOSFET low-side driver in the ECU. So either the brake pedal switch and the a brake light bulb can cause an EPC error along with the aforementioned fuel supply components. It's best to have a diagnostic tester to check for DTC errors via the DLC connector. It would at the very least steer you in the right direction to fix your EPC problem effectively.

Electronic Power Control (EPC)

It was very surprising to discover how many thousands if not millions of car owners out there, have no idea exactly what  Electronic Power Control (EPC) is. Yet most of them would like to know what the Electronic Power Control (EPC) circuit really does , more especially the Volkswagen, Audi, Seat and Soda owners. 

Considering they've been plagued by the Electronic Power Control (EPC) light, limp mode, DTC errors and poor engine performance to the point of frustration and panic for a number of years. Nobody seems to be able to give them good advice or practical guidance; and in many cases not even the Volkswagen, Audi, Seat and Skoda agents can. 

Leaving VW owners confounded, disappointed and disillusioned by their choice in cars, which results in so many car owners swearing, never to invest in VW brands ever again.

Unscrupulous motor mechanics tend to take advantage of these situations, recommending that the car owner brings their car to them as soon as possible before damage occurs to the engine.  Whereas in fact, the Electronic Power Control (EPC) is a safety circuit designed to prevent damage to the engine. 

When the  Electronic Power Control (EPC) mode does engage, it can and often does affect the car's stability and cruise control and torque circuit giving the impression there is a lot more wrong than there actually is. 

Since the Electronic Power Control (EPC) is "yellow" and not red, it acts more as an advisory light rather than a warning light, even though everybody tends to call it a warning light. A  flashing amber light is considered a "warning signal" but still doesn't have the danger status of "red warning light". 

 


Technically the "yellow" Electronic Power Control (EPC) light is in fact  amber which is a blend between orange and yellow. Car dashboard light colours can be roughly divided into three categories. 

Warning lights are Red in colour. Advisory lights are  amber in colour and information lights are generally either white, green or blue in colour. Having said that, its simple to understand that amber implies that you should keep an eye on, or be prepared for either  a reduction in power or  interruption to power.

Hence, Amber lights are used as Indicator lights (flashers) on cars for the turn signal and hazards. Amber lights are also used by roadside breakdown vehicles to alert drivers. An amber traffic light is generally considered a cautionary light, signalling  readiness to stop. Much like an amber  traffic light does. 

Now that you know what the colours of the lights imply, allow me to give you the low-down on Electronic Power Control (EPC) itself. EPC is an acronym and it is the official abbreviation for Electronic Power Control. 

Electronic Power Control is an embeded system, specifically designed into electronic circuits that permits it be part of a larger electro-mechanical system.  An Electronic Power Control system can also simply be described as a self-contained "feedback" circuit.  

It can even be further  explained, as a microprocessor based electronic circuit -or a computer if you like- that alters its output bias based on its inputs. Its "status quo" or current baseline is taken as a reference point and the objective is to control its operation within its predetermined parameters, and as close as possible to the said baseline, based on the signals from its inputs. 

Should any of these inputs, that predominantly come from sensors fail, for whatsoever reason, the computer circuit wouldn't be unable to complete its processes and would either enter into a "compensatory state", a "warning state" or an "error state". But more about this later!

The Electronic Power Control circuit has become standard equipment as part of the OBD-II (On-board Diagnostics 2) system in all modern day cars, manufactured since 1996. The Electronic Power Control is an integral part of every computerized ignition and engine management system, embedded into the ECU (elcectronic computer unit). 

The Electronic Power Control (EPC) dashboard advisory light is also part of this system and is normally activated by errors in the vehicle's torque circuit but not exclusively. The Electronic Power Control (EPC) light is  actually  a "new" addition to the plethora of light on the more modern vehicle's dashboards, a light  that gives any driver a sense of despair when it turns on. 

But more about that later ...

However, since a full blown explanation is outside the scope of a single blog-post, it is imperative that you need to read  every blog installment or the entire blog to get the full Electronic Power Control (EPC) picture.

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Annoying VW EPC light

VW EPC expounded

As I've explained in an earlier blog, the amber Electronic Power Control warning light on your car's instrument cluster, is just an indicator light; drawing your attention to either (1)  an Auto-Correct EPC Problem, (2) a Pending EPC Problem, (3) an Existing EPC Problem or  (4) a Current EPC Problem. 

An Auto-Correcting  EPC problem occurs when the EPC light goes on without noticeable difference in engine performance and goes off during subsequent drive cycles which may be within a day or two or longer.

A Pending EPC Problem could be something as simple as a spark plug misfiring intermittently and appears in the scan list but after a while becomes an Auto-Correcting EPC problem alternatively if the plug continues to misfire it becomes and Exising EPC problem.

An Existing EPC Problem could be something like the MAF sensor or a accelerator pedal sensor that needs cleaning or replacement and a Current EPC Problem normally results in limp mode.

EPC light is bright YELLOW/AMBER and acts as a indicator, it is not as a warning light. 
Warning light are always RED.

EPC light is bright YELLOW/AMBER and acts as a indicator light, an advisory light; it is not as a warning light.  Warning light are always RED. Since the ECU "learns your driving style" over time, it records your optimize drive cycles to non-volatile memory along with atmospheric pressure, min & max rpm and the average fuel use data, etc, then creates an adaptive pattern or map based on these parameters. 

When this map is compared to sudden spirited driving, it may trigger the EPC light but will auto-correct (reset) itself after a few driving cycles within a day or two. Sometimes the EPC light may be accompanied by the Check Engine Light (CEL).

A Pending Problem can cause the EPC light to come and not switch off on its own. Pending implies that the problem will only get worse if left unattended to. A diagnostic scanner is needed to view the DTC error, hence its really worthwhile investing in one. 

For example, assume that cylinder number 3 randomly misfired a few times as the pending problem. The scan freeze frame data will show something like this.

000771 - Cylinder 3

               P0303 - 000 - Misfire Detected - Intermittent

             Freeze Frame:

                    Fault Status: 00100000

                    Fault Priority: 2

                    Fault Frequency: 7

                    Reset counter: 255

                    Mileage: 38187 km

                    Time Indication: 0

                    Date: 2021.11.05

                    Time: 21:09:58

             Freeze Frame:

                    RPM: 758 /min

                    Load: 13.1 %

                    Speed: 0.0 km/h

                    Temperature: 51.0°C

                    Temperature: 33.0°C

                    Absolute Pres.: 830.0 mbar

                    Voltage: 12.435 V

What this means is that cylinder misfired 7 time, and that the most recent misfire occurred at the displayed time and date highlighted in red and has a fault priority of 2.  Fault priority of 4 or lower needs to be attended to immediately since it affects the driveability of the car. Don't ignore the VW EPC light.  

Fault priority of 5 and above doesn't require immediate attention but must be attended to sooner rather than later. The freeze frame date shows that the car was idling and 758 rpm with the speed at 0 kph and that the engine hasn't reach its optimum operating temperature as yet. In a nutshell, freeze frame captures the engine operating conditions at the time when the EPC error occurred.

An Existing EPC Problem could  mean either the throttle pedal, throttle body, or brake control unit or any other circuit related to the torque circuit, like the  cruise control unit or the traction control unit is misbehaving.  However the EPC light can also indicated an unrelated problem like a loose fuel cap. With the EPC light on, and a pungent fuel smell inside the cockpit would point you to fuel cap.  

Since the fuel is under pressure, the fuel pump, fuel regulator or fuel rail pressure sensor may also be suspect, each should be excluded through a process of elimination. Remember the Electronic Power Control system is integrated with several other systems on you vehicle, like the steering control unit and the ECU, hence it's not always easy to diagnose.

Its permissible to  drive your VW for a short distances and for a short period of time after the EPC light has triggered, that's to say if driveability hasn't been impaired but its best to either fix it yourself or take it to  VW service center. An  EPC dashboard light can be caused by any of the following, but in no particular order. Sometimes both the EPC light and CEL (check engine light) would turn on.

1) Brake Light Switch failure

2) Mass Air Flow Sensor failure 

3) Engine Speed Sensor failure 

4) Throttle System Potentiometer Failure

5) Cruise Control failure

6) Accelerator Pedal Potentiometer failure

7) Repeated cylinder misfires

8) Loose fuel cap

9) Blown / Faulty  brake light

Any of these can and may cause your vehicle to go into “limp mode” which can be described as a Current EPC Problem. When limp mode strikes, the Engine Control Unit will limits the functions of the torque circuit and transmission thus prevent your VW's engine from  revving higher than 2000 rpm and limit its speed to 30-45 kpm. 

Some mechanics would reset the EPC light by cleasing the DTC list without fixing the actual problem but this is not recommended. When the  Diagnostic trouble codes (DTC) are cleared,  "your driving style" map is also deleted, meaning that the ECU would have to relearn  "your driving style"  from scratch and your VW's performance may seem a bit off.  That's to say, until your racked up sufficient drive cycles (data) with which the ECU can do an analysis in real time. 

Grand Theft Auto

Volkswagen (VW) motor vehicles are not only popular among car enthusiasts, they  are also very popular car among the first-time car-buying youth. That said, VW vehicles have also become most popular car among car thieves to steal.

According the Crime Statistics Report for the years 2020 and 2021 - released by the South African Police Service (SAPS)- motor vehicle theft in general has steadily increased since 2011. However, it is correct thinking to assume that thieves have a preference to certain make and model of car.  Case in point - both the VW Polo hatchback and VW Polo sedan are at a higher risk of being stolen than any other VW model and other manufacture's vehicles as a whole.  

VW Polo Hatchback

Since its release in 2018 the VW Polo Hatchback had become the most stolen cars in South Africa. By 2019 it was the most sold passenger vehicle; targeted by "chop-shops" -illegal garages that buy stolen cars - to disassemble them and sell their individual components for profit - aka midnight spares. 

The new VW Polo hatchback - front-wheel drive, 5 door with 5 seats, powered by a 2.0L TURBO 4 engine that outputs 147 kW of power and 320 Nm of torque costs roughly between R320K and R480K whereas a older model or one with  a lower capacity can sell for anything from R170 000 and R250 000 subject to millage and overall condition.

VW Polo Sedan

The VW Polo sedans comes in as either Trendline, Comfortline, Highline and are essentially the sedan version of the  VW Polo hatchback with and engine capacity of either 63 kW  of 77kW fetching a price between R270k and R350k.

Insurance

Loosing a vehicle of this calibre with such a pricetag can be really gruesome hence a condition of any hire-purchase agreement to keep the vehicle adequately insured but an anti hijack immobilizer and alarm system is also essential. Car insurance coupled to Life Insurance may also be highly advantagious.

Anti-theft Alarm, Remote Central Locking and Remote Central Locking are not standard features of all models but the all do come with an Immobilizer but without Automatic Door Lock. It is therefore feasible to invest in an anti-Blocker, anti-Signal, anti-Jammer engine immobilizer with vehicle tracking GPS tracker support and engine cut in preference of the factory fitted product.

Transponder detection

Since most later vehicles are fitted with receiver and transponders chips, stealing a car without having its corresponding key is quite difficult.  If the key isn't close to the steering column stalk that houses the receiver coil or not within key detection distance then engine will not start.  Thieves also resort to key re-programmers and signal grabbers to counteract new technologies like ‘push to start’ buttons installed in the later model vehicles.

Carjacking

So, in order for thieves to steal your car they would have to take it from you by force  - hijacking, a horrific experience. Most cars today are stolen that way by hijacking the driver. If the thieves don't have the matching ignition key, the immobilizes prevents them from starting it by inhibiting the starting process, hence they take the car from the driver with key by force -carjacking. 

Safety Tips to prevent a possible hijacking

Before getting into your car, look around for any any suspicious characters. Should they be around alert a friend, family member or neighbour, even get them to accompany you.

Hijackings are often than not planned, so be be vigalent and cognizant of vehicles following you even at a distance.

Jot down the number plates of vehicles that or that continually pop up on your daily travels and check against previous ones.

Report any s suspicious activity to your local neighbourhood watch or security company of police.

Make sure that you are not being followed before driving into your driveway where you could be cornered.

Alert someone at home before driving into your driveway, to come outside to observe if there are suspicious characters lurking about.

Always be aware and alert of your surroundings before getting out of your car.

Never stop or park your car in a way that you cannot get away from someone following you quickly. 

Be aware of any vehicle blocking your driveway as you pull into it. Honk your hooter constantly to alert neighbours. It may be sufficient to scare them off.