Autotek Electronics

Autotek Electronics is a supplier of electronic automotive parts. We can repair and supply ABS,ECUs, and instrument clusters for all makes and models of car.

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Typical faults found in your car:

Typical faults that may occur on different vehicles can include:

Poor idling - The idling of vehicle is maintained using the Idle Air Control Valve (IACV) and / or TCS (Throttle Control Switch). Beware of causes of poor idling that can include an intermittent Ignition Coil, a bad O2 Sensor, a Vacuum Leak, Burnt Valves, Dirty or Burnt Plugs, a short on the Distributor Cap or Ignition Coil, or a bad Fuel Injector. A common cure for such an issue is a good emissions service at your local dealer.

Engine Not Cranking - this is where the engine will not turn over and start, and it may be accompanied by a warning light on your dash, such as an Engine Management light. Causes of this can include a faulty battery or starter motor (a battery can be simply tested by switching lights and indicators on and off), a lack of fuel or compression, or a broken timing belt or chain. Checks for these faults are usually the best port of call to begin with.

No Spark - this is when the engine cranks normally, but will not start because of a lack of spark, or it starts then stalls instantly. This may be caused by broken / loose / corroded wires from the pickup to the ignition module / PCM, a bad CKP / Crankshaft Position Sensor, or a bad rotor or distributor cap (cracks or carbon tracks that are allowing the spark to short to ground).

No fuel - This is where no fuel is able to reach the engine in order for it turnover and run. Common causes of this problem include a bad fuel pump / relay, Bad inertia fuel shut-off safety switch (Shuts off fuel in an accident, may have been tripped by a severe jolt, press button to reset), an open in wiring anywhere in fuel pump wiring circuit (power or ground), bad fuel, plugged / pinched fuel line or fuel filter, a leaky fuel pressure regulator, No power to Fuel Injectors (Due to faulty fuel injector relay, blown fuse, no input signal to PCM from crank position sensor or cam position sensor, or bad PCM driver circuit), Injectors should usually have power when key is on. PCM grounds other side of injector circuit to pulse the injectors. Also a major vacuum leak can cause bad fuel (An open EGR valve, disconnected vacuum hose, PCV valve, etc, can create a large vacuum leak and allow too much air to be sucked into the engine. This will make the air/fuel mixture too lean and make the engine hard to start. Engine will usually idle rough if it does start.

Engine cutting out when hot - this could be caused by a faulty MAF Sensor, bad Cam Position Sensor / Crankshaft Position Sensor, faulty Lambda Sensors, or a dirty Idle Air Control Valve (IACV).

Cold start problem - this is where a vehicle may struggle to start in cold weather conditions. It may be caused by an intermittent fault throttle body, a faulty idle valve or a fault coolant temperature sensor (CTS).

ABS / TCS lights staying on - this is where the Anti-lock Braking System or Traction control System warning lights stay lit on your instrument cluster. This can be caused by faulty wheel sensors (there is one on each wheel) or faulty wiring to the sensors from the ABS Pump/Modulator, a poor earth connection which can cause damage to the ABS Control unit, a burnt out motor (due to the modulator block seizing if the ABS system is not engaged often enough) which can overload the control unit, brake fluid changed incorrectly (causing non return valves to seize up and the modulator block to leak), or a faulty BAS (Brake Assist System). If the modulator block does seize up, it can have symptoms of the brake pedal moving away from your feet as though there is a leaky master cylinder. A side note is that some vehicles use the speedometer signal from the ABS ECU to operate the speedo, and also the Automatic transmission control module (common in Merecedes vehicles).

Engine ECU / Check Engine warning Light staying on - this problem occurs when the self check diagnosis of your vehicle fails for some reason, such as a problem with the emissions (see previous faults), an engine misfire, or a fault with the Engine Management ECU itself. As a rule, the light stays on as a result of a problem with the vehicle emissions.

Battery Charging Light - this light will come on if there is a fault with the battery charging system. This fault can be caused by a broken alternator belt or a fault with the alternator itself, dirty / bad battery connections, a poor earth connection, a faulty voltage regulator (typically on Mazda and Ford where the voltage regulator is built into the Engine Management ECU), or a fault with charging / overcharing protection relays. A fault with the protection relays may also cause further damage to the vehicle, in particular to any of the ECUs.

Diesel ECU fault - many modern diesel vehicles are fitted with a Diesel Control Unit alongside a high pressure pump, with later versions known as a Diesel HDI system. All diesel engine management systems are fitted with glow plug driver circuits, and most diesel engines are now fitted with turbo systems. A fault with any of these systems or modules can cause an ECU issue.

A good way of diagnosing a typical fault with most modern vehicles is to use a diagnostic tool and check for any fault codes. The fault codes given will often relate to a typical problem on the car.

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Instrument Cluster/Speedo/Rev Counter

Speedo / Instrument Cluster

Dashboard / Rev Counter / Gauge

Often refered to as an Electronic Instrument Cluster or Digital Dash, the Instrument Cluster is a set of guages or readouts (analog or digital) typically located on the drivers side of the vehicle behind the steering wheel.

Typical features that an Instrument Cluster might contain are a Fuel Guage, Rev Counter, Speedometer, Tachometer or even a Trip Computer. Most vehicles today have a combination of analog guages and digital readouts.

A Trip computer is a digital display that contains information about factors such as outdoor temperature, travel direction, fuel economy, RPM, odometer (total mileage reading), or distance to empty.

Some features (particularly digital displays), are now being moved to the centre console, with the arguements for this being that it will save money for manufacturers who make left and right hand drive versions of their vehicles.

Typical Instrument Clusters now may contain the immobiliser curcuit for the vehicle, which is a security system used in cars to identify when a correct key has been inserted into the ignition; and will then start the engine appropriately.

As an additional security measure, many Instrument Clusters are now coded to the vehicle, which means they cannot be forceably removed from their currect car, and then replaced onto another, without transfering the code (this is typically only allowed by using a diagnostic tool or some equipment possessed by the main dealer of the vehicle).

This is also done to ensure people cannot swap mileage readings by replacing the dash.

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Air flow meter/air mass sensor

Air Mass Sensors

Applications:-

The air mass sensor measures the mass of air inducted by the engine (air flow mass) with great precision. The signal produced by the air mass sensor is used to calculate the amount of fuel injection and in the case of diesel engines also to control the recirculation of exhaust. It is an important component in both the reduction of exhaust and air supply. A defective or dirty air mass sensor can deliver false input signals to the engines central control unit, which in turn sends false information to other components. In case of turbo diesels the air mass sensor is subject to particularly high burden due to the fact the both air flow rate and air speed are very high.

Description of functions:-

The complete air mass sensor consists of a flow channel (pipe) in which the inducted air-flow is directed past the actual sensor. Depending on the type of use and vehicle, the air mass sensor is either completely integrated in a tube made of synthetic material, or with the actual sensor as a separate individual plug in module. Both versions (with tube/separate) are termed air mass sensor.

Earlier Models were fitted with a hot-wire sensor element. The hot-wire was burn free by polluants following the short increase in heat after turning off the engine. Newer Models work using a film like heating resistor on a support, in which case the burn-through procedure does not apply.The heat-film sensor is heated to a temperature of approx 120-180 degrees Celsius above induction temperature (depending on vehicle manufacturer) the inflow of air cools the heat-film sensor. This cooling down is compensated by heating current via the electronic controller unit. This heating current is directly proportional to the amount of air induced.

Defects and possible causes:-

Defective and dirty air mass sensors deliver faulty signals. This can have the following consequences:

Black Smoke

Power Shortage

Minimal operation

Possible causes of damage:

If the air intake tube is porous, dirt particles can find their way into the inducted air. These collide at high speed with the air mass sensor, destroying the sensitive sensor element. Excessive oil spray from the crankshaft ventilator can lead to fouling-up of the sensor. Bad servicing, for instance un-cleanliness when changing air filters, use of wrong or substandard air filters can be the cause of dirt and damage to the air mass sensor. Splashed water, for instance from heavy rainfall, can force its way into the clean-air side and damage or dirt-clog the sensor. Salt water caused by winter gritting and melting snow increases this effect. Oil particles from oil-covered sport air filters can damage or dirt-clog the sensor.

Other sources can also cause an intact air mass sensor to deliver a false signal:

defective exhaust-gas recirculation valves

defective fuel tank ventilation valves

porosity of induction tract

clogged air filters

Air flow measurement

Volume air flow (VAF) sensor:-

The VAF sensor is fitted between the air filter and throttle body. It measures the amount of air drawn into the engine by the deflection of a flap inside the sensor.

Operation:-

The flap is connected to a potentiometer which sends a signal voltage to the ECM.

This is the primary signal which, in conjunction with those from the other system sensor, is used to determine the fuelling requirements of the engine.

In many applications the air temperature sensor is incorporated in this type of air flow sensor

The MAF sensor has no moving parts and provides very little restriction to the air flow. It is fitted between the air filter and throttle body.

The MAF sensor consists of venture with a resistance wire exposed to the incoming air.

An air temperature sensor or compensating wire is also exposed to the air flow.

The ECM senses changes in temperature caused by variation in air mass passing through the sensor body and increases or decreases the current flowing through the measuring wire.

An internal electronic circuit maintains the approximate tempreture of the measuring wire at a constant 120 C, above the intake air temperature.

As the mass of air passing the wire increases, so the current required to maintain the temperature also increases.

This increase in current is sensed by the ECM.

This is the primary signal, used in conjunction with signals from the other system sensors, for determining the correct amount of fuel to be supplied to the engine.

A "burn-off" facility operates when the system is switched off, to remove dirt from the filament.

Mass air flow (MAF) sensor hot-film type:-

Similar to the hot-wire type, but with the measuring element incorporated in ceramic plate. This arrangement obviates the need for a "burn-off" facility.

Manifold absolute pressure (MAP) sensor:-

Connected by vacuum hose to the engine inlet manifold. Usually located in the engine bay, or built into the ECM casing.

Operation:-

The sensor consists of a diaphragm and piezo-electric circuit which varies the resistance in proportion to the pressure in the manifold.

The sensor has a 5 volt supply and sends a signal voltage to the ECM which is proportional to the manifold pressure.

The ECM uses the voltage signals from the MAP sensor to adjust the signals to the injectors.

Idle air control (IAC) valve:-

The auxiliary air valve allows air to by-pass the throttle valve when the engine is cold, to increase idle speed during the warm-up period. Idle speed control devices are usually fitted into a throttle by-pass system, allowing extra air to enter the engine. This extra air complements the mixture enrichment during a cold start and the subsequent warm-up period. Some single point systems have a motorised actuator, which opens or closes the main throttle valve, by very small amounts, to control he idle speed.

Operation:-

The valve is mounted on the engine in a position where it is in direct contact with engine temperature.

The valve incorporates an electrically heated bi-metal strip which determines the cut-off point as the engine reaches normal operating temperature.

Idle air control (IAC) valve solenoid type:-

The auxiliary air valve allows air to by-pass the throttle valve when the engine is cold, to increase idle speed during the warm-up period.

Operation:-

The valve is mounted on the engine in a position where it is in direct contact with engine temperature.

The valve incorporates an electrically heated bi-metal strip which determines the cut-off point as the engine reaches normal operating temperature.

The solenoid idle air control actuator allows air to by-pass the throttle valve to govern the idle speed, under all conditions.

Operation:-

It is controlled directly by ECM, which interprets signals from sensors such as RPM and coolant temperature to maintain the idle speed at a pre-determined level. The solenoid acts against a spring, either with a rotary or linear action.

Idle air control (IAC) valve rotary type:-

The rotary idle air control actuator allows air to by-pass the throttle valve to govern the idle speed, under all conditions.

Operation:-

The device consists of rotary valve, in the by-pass air way, mounted on the shaft of a special electric motor.

The motor has two sets of armature windings and is limited to an angular movement of 90C.

The ECM supplies an alternating voltage to the two windings, depending on signals from sensors such as engine RPM and coolant temperature.

The alternating voltages exert opposing forces on the armature resulting in the valve taking up a position corresponding to the voltage radio.

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Throttle Body

Throttle Body

The idle speed control actuator motor positions the main throttle valve to control the idle speed.

Operation

In a fuel injection engine, the throttle body is the part of the air intake system that controls the amount of air flowing into the engine, in response to driver input. While the accelerator is often called a "gas pedal", it would be more accurate to describe it as an "air pedal".

The throttle body is usually located between the air filter box and the intake manifold, and usually attached to, or near, the mass airflow sensor.

The largest piece inside the throttle body is the throttle plate, which is a butterfly valve that regulates the airflow.

On many cars, the accelerator pedal motion is communicated through the throttle cable, which activates the throttle linkages, which moves the throttle plate. In cars with electronic throttle control (also known as "drive-by-wire"), an electric motor controls the throttle linkages and the accelerator cable connects not to the throttle body but to a sensor. The Engine Control Unit (ECU) determines the throttle opening. On some modern cars, the accelerator cable is replaced by a pedal position sensor, which sends the pedal position to the ECU.

When the driver presses on the accelerator pedal, the throttle plate opens up, allowing more air into the intake manifold. Either a throttle position sensor or an airflow sensor measures this change and communicates with the ECU. The ECU then increases the amount of fuel being sent to the fuel injectors in order to maintain the desired air-fuel ratio.

Throttle bodies may also contain valves and adjustments to control the minimum airflow during idle. Even in those units that are not "drive-by-wire" there may be a small electric motor that the ECU uses to modify the throttle opening.

Many cars have a single throttle body, however more than one may be used, chained together by linkages, to improve throttle response. At the extreme end, cars such as the BMW M1 have a separate throttle body for each cylinder.

A throttle body is somewhat analogous to the carburetor in a non-injected engine. Carburetors combine the functionality of the throttle body and the fuel injectors into one, that is, to modulate the amount of air flow, and to combine air and gas together. Cars with throttle body injection (called TBI by General Motors and CFI by Ford) locate the fuel injectors in the throttle body, thereby allowing an older engine to be converted from carburetor to fuel injection without altering significantly the engine design.

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Automatic Transmissions

Transmission Control Unit

A Transmission Control Unit is a device that controls modern electronic automatic transmissions. A Transmission Control Unit generally uses sensors from the vehicle as well as data provided by the Engine Control Unit to calculate how and when to change gears in the vehicle for optimum performance, fuel economy and shift quality.

Electronic automatic transmissions have been shifting from purely hydromechanical controls to electronic controls since the late 1980’s. Since then, development has been iterative and today designs exist from several stages of electronic automatic transmission control development. Transmission Solenoids are a key component to these control units.

The evolution of the modern automatic transmission and the integration of electronic controls have allowed great progress in recent years. The modern automatic transmission is now able to achieve better fuel economy, reduced engine emissions, greater shift system reliability, improved shift feel, improved shift speed and improved vehicle handling. The immense range of programmability offered by a Transmission Control Unit allows the modern automatic transmission to be used with appropriate transmission characteristics for each application.

Input Parameters:-

The typical modern Transmission Control Unit uses signals from engine sensors, automatic transmission sensors and from other electronic controllers to determine when and how to shift.

Vehicle Speed Sensor

(VSS) This may also be known as an output speed sensor (OSS). This sensor sends a varying frequency signal to the Transmission Control Unit to determine the current shaft speed of the output shaft or differential in a typical vehicle. The Transmission Control Unit uses tire size, gear ratios and final drive ratio to calculate the current vehicle speed.

Turbine Speed Sensor

(TSS) This may also be known as an input speed sensor (ISS). This sensor sends a varying frequency signal to the Transmission Control Unit to determine the current shaft speed of the input shaft or torque converter. The Transmission Control Unit uses this shaft speed to determine slippage across the torque converter and potentially to determine the rate of slippage across the bands and clutches.

Transmission Fluid Temperature

(TFT) This may also be known as Transmission Oil Temperature (TOT). This sensor determines the fluid temperature inside the transmission. This allows the Transmission Control Unit to modify the line pressure and solenoid pressures according to the changing viscosity of the fluid based on temperature. This can provide for more appropriate shifing in extreme temperatures and allow for temperature failsafe systems to take control.

Output Parameters:-

The typical modern Transmission Control Unit sends out signals to shift solenoids, pressure control solenoids, torque converter lockup solenoids and to other electronic controllers.

Shift Solenoid

Modern electronic automatic transmission have electrical solenoids which are activated to change gears. These solenoids range from very simplistic control in older automatic transmission designs to extremely complicated in very new automatic transmission designs. The way in which the solenoid is activated and when it is activated is chosen by the manufacturer of the transmission and can vary greatly from vehicle to vehicle.

Pressure Control Solenoid

Modern electronic automatic transmissions are still fundamentally hydraulic. This requires precise pressure control. Older automatic transmission designs may only use a single line pressure control solenoid which modifies pressure across the entire transmission. Newer automatic transmission designs often use many pressure control solenoids and sometimes allow the shift solenoids themselves to provide precise pressure control during shifts by ramping the solenoid on and off. The shift pressure affects the shift harness and shift speed.

Torque Converter Clutch Solenoid

(TCC) Most electronic automatic transmissions utilize a TCC solenoid to lock the torque converter electronically. Once locked, the torque converter no longer applies torque multiplication and will spin at the same speed as the engine (assuming the converter is fully locked). This provides a major increase in fuel economy and modern designs attempt to provide partial lockup in lower gears to improve fuel economy further.

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ABS Pump/ECU/Modulator

Anti-lock Braking System (ABS)

An anti-lock braking system (ABS) is a system on vehicles which prevents the wheels from locking whilst braking. The purpose of this is to allow the driver to maintain steering control under heavy braking and in most situations, to shorten braking distances (by allowing the driver to hit the brake fully without the fear of skidding or loss of control). Disadvantages of the system include increased braking distances under certain conditions and the creation of a "false sense of security" among drivers who do not understand the operation and limitations of ABS.

History

Anti-lock braking systems were first developed for aircraft. An early system was Dunlops Maxaret system, introduced in the 1950s and still in use on some aircraft models. This was a fully mechanical system. It saw limited automobile use in the 1960s in the Ferguson P99 racing car, the Jensen FF and the experimental all wheel drive Ford Zodiac, but saw no further use; the system proved expensive and, in automobile use, somewhat unreliable. However, a limited form of anti-lock braking, utilizing a valve which could adjust front to rear brake force distribution when a wheel locked, was fitted to the 1964 Austin 1800. The first car (worldwide) to have ABS fitted as standard (across the entire range) was the Ford Granada Mk 3 (of 1985).

The American firm Kelsey Hayes (now part of TRW Automotive), developed the first electronic ABS system in the late sixties and introduced on the 1970 Lincoln Town Car. It was a rear wheel system, as was General Motors Cadillac version of anti-lock brakes called Track Master, which was introduced in 1970 on the Eldorado coupe and made an option for the entire line in the following year.

The first true electronic 4-wheel multi-channel ABS was co-developed by Chrysler and Bendix for the 1971 Imperial. Called "Sure Brake", it was available for several years and had a satisfactory performance and reliability record. The German firm Bosch had been developing anti-lock braking technology since the 1930s, but the first production cars using Boschs electronic system became available in 1978. They first appeared in trucks and the Mercedes-Benz S-Class. Interestingly, M-B has recently advertised that it had 4-wheel ABS first, when, in reality, they were beaten by seven years - by a company they now own: Chrysler. BMW started using ABS at the time, making the technology standard on all vehicles in 1986. ABS Systems were later introduced in other vehicles.

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Engine Management ECU

Electronic Control Module/Unit (ECM/ECU)

The ECM controls the delivery of fuel and the timing of ignition spark. It receives information from several different sensors from the vehicle and processes this information to provide optimum performance from the engine. Electrical signals from the fuel and ignition system sensors are received and processed by the electronic circuits in the ECM.

Functions:-

Depending on the vehicle model some or all of the following will be fitted:

Engine coolant temperature (ECT) Sensor

Intake air temperature (AIT) sensor

Throttle Position (TP) sensor

Load sensor volume/mass air flow (VAF/MAF) sensor manifold absolute pressure (MAP)sensor.

Vehicle speed (VSS) sensor.

Crankshaft position (CKP) sensor.

Camshaft position (CMP) sensor

Engine speed (RPM) sensor

Oxygen sensor (O2S)

Knock Sensor (KS)

Barometric pressure (BARO) sensor.

Depending on the vehicle the output from the ECM will control some or all of the following:

Injectors by controlling the length of time each injector valve remains open. Fuel pump relay Idle speed control system. Evaporative emissions system Exhaust gas recirculation system. Ignition timing and knock sensing. Intake manifold length. Self-diagnosis of faults, indicated by an LED on the ECM or a malfunction indicator lamp (mil) or check engine warning light on the instrument panel. Emergency "limp-home" programme, which substitutes an average value for any failed primary sensor enabling the vehicle to be driven to a workshop for correction.

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Autotek Electronics

We are an automotive electronic parts supplier, specialising in Engine Management ECUs, ABS Pumps,ECUs and Modulators, Throttle Bodies, Instrument Clusters, as well as repairing all types of ECU, ABS and Instrument Clusters