Service Section Technical Pages

  • Engine Tuning & Diagnostics in Shropshire.
    Tel 01743 884888

    Mobile Service  for Computerised Vehicle Diagnostics using professional test equipment with latest software updates.        ..........More info

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    Drivers and fleet operators require the best performance from their vehicle for comfort , reliability and fuel economy.

    Problems with the vehicle engine management, fuel & ignition systems may cause

  • Difficult Starting
  • Engine Misfire   (Ignition misfire may set P0300 fault code)
  • Intermittent stalling of the engine
  • Loss of engine performance & sluggish acceleration
  • Engine temperature faults eg, overheating
  • Poor fuel economy
  • Illumination of the check engine light (also known as MIL or Malfunction indicator lamp )  
  • MoT test exhaust emissions check failure due to excessive CO (Carbon Monoxide) or HC (Hydrocarbon) content in exhaust gas




    Remapping of engine control software for better performance
    The software control parameters of  electronic engine management systems are stored within the vehicle on board computer as a "map".  Vehicle manufacturers software is often programmed to provide low emissions and driveability over a wide range of  operating conditions.

    Performance upgrades are available which allow specific changes to the original software to meet individual driving requirements.

    Driving cycle and engine control mapping

    The driving cycle will have a huge impact on the type and frequency of servicing needed.
    A vehicle operating on frequent short journeys may not reach normal operating temperature before it is stopped and may also suffer from battery charging system problems.
    A build up of carbon and sludge deposits in the intake manifold can cause blockages and restrictions leading to malfunction of items such as idle speed control motor , throttle flap,and exhaust gas recirculation (EGR) valve etc.
    Manufacturers often develop engine management software for production cars to optimise fuel efficiency combined with low exhaust emissions.
    Performance vehicles developed to compete in motorsport may be operated with modified engine control software maps written to provide increased fuelling and power output often at the expense of driveability.


    Extended Service Intervals ? Service Light Reset

    Manufacturers develop extended service intervals to reduce operating costs.
    Many newer vehicles are equiped with a service indicator light to prompt the operator when a service or inspection is due based on a time or mileage or engine running hours calculation.

    The computerised engine management fitted to the modern vehicle allows improved fuel consumption and reduced maintenance because ignition timing, fuel mixture, and idle speed are electronically controlled.
    Sensors & Actuators
    Inputs from sensors measure driver demand (throttle position), engine temperature (coolant temp), engine load (manifold absolute pressure), mass air flow and air temperature, exhaust gas emissions (Lambda), vehicle speed ,etc.

    The inputs are carried along wires to a central computer, (ecu) where the received signals are processed and compared to programmed  values stored as a memory map, then output values calculated and sent along wires to output actuators such as fuel injectors, control pressure regulator , cooling fan, idle speed control ,etc, to maintain performance factors such as smooth engine running, fuel economy, and low exhaust emissions.

    What causes problems with engine management?

    Various things can affect the efficient running of your vehicle:

  • Vibration
  • of the engine or vehicle body can cause wiring harnesses and pipes to move and chaff against other components leading to wiring insulation damage , and eventually corrosion or breakage of wires. Damaged wiring insulation may cause a short circuit between power and signal or ground wiring.
  •  Road salt and moisture can enter wiring connections leading to corrosion , high resistance, and low voltage faults.
  • A scan tool test to retrieve   fault codes stored as history by the vehicle computer may indicate a component low voltage or open circuit or short circuit code identifying  the area the where a fault exists.
  • Build up of carbon deposits due to the operation of exhaust gas recirculation systems can also cause problems with air intake
  • Fuel quality will affect component life. Moisture or contamination in fuel can lead to corrosion which may be detrimental to precision machined components particularly in high pressure fuel injection systems. Signs can be metal particles in the fuel filter or fuel tank indicating component wear.

  • Manufacturer Software Updates

    When manufacturers develop a new vehicle model there may be unforeseen problems which only show after the effects of wear and tear. These problems which develop may affect exhaust emissions or driveability can sometimes only be corrected be updating the control unit software, in similar fashion to updating the drivers on a pc.

    The type of microcontroller chip inside the control module will determine the method required to update software. In some cases this may require replacement of the program microchip , but on later vehicles updated software may be 'flash' programmed via the diagnostic connector using a pass-thru programming technique.

    Certain faults which occur to a particular vehicle model may alert the manufacturer to release a TSB or Technical Service Bulletin.

    Updated calibration software is downloaded from the vehicle manufacturers website and transferred to the vehicle computer using either a dedicated tool or a computer and SAE J2534 (refers to Society of Automotive Engineers protocol) compliant interface

    How we can help: Retrieval of fault codes using scan tools ,  further diagnostic testing and repair process


    Check Engine light on:
    The check engine light illuminates because the vehicle onboard computer has recognised a fault with part of the vehicles engine management system or engine operating parameters. The fault may be historical or current.
    The fault will be logged in onboard computer memory and stored as a fault code.

    Fault code retrieval:
    First process is to liase with the customer for a description of the concern, then retrieve both manufacturer and eobd stored fault codes from the engine control unit using scan tool diagnostic equipment and record details of the stored codes. In some cases eobd data can be used to indicate under what conditions the fault code was logged eg engine rpm, etc.
    Next, the scan tool is used to clear the recorded historical fault codes from onboard (obd) computer memory. This is done because people often have a go at repairing faults themselves without access to diagnostic test equipment and by unplugging sensors can log false codes onto the obd computer memory.

    A visual check on the engine is carried out with reference to stored fault codes before the engine control unit memory is rechecked to see if any fault codes immediately re occur. Appropriate action to investigate & rectify the cause of the fault code(s) can be taken subject to customer liason and approval.
    Many systems can be tested further by use of dynamic data recording and individual actuator testing (used to check individual wiring & components).

    A misfire may be caused by faulty electrical components, a defect within the air induction ,fuel delivery, or exhaust systems, or by mechanical component failure.
    We have both advanced and basic test equipment which can aid the technicians diagnosis and rectification of these faults.

    Lack of Performance, excess fuel consumption, etc.
    Can be caused by items requiring minor adjustment and routine maintenance due to wear, or by component or circuit failure.
    We have a wide range of test equipment to aid further diagnosis & repair.

    Typical engine management parameters that can be checked using a scantool

    Read ECU identitity
    Software version . Variant coding
    Hardware version.

    Immobiliser Key code

    Check the immobiliser key code has been received by the ECU

    Fault Code Display
    Read Historical & Current fault codes stored in ECU memory using K line (serial data) and L - line (activates data output).
    Erase fault codes.
    Throttle position sensor
    Check range from Zero to Full throttle using dynamic data will display if the potentiometer track is faulty.

    Check output voltage.
    Operation can be further verified using oscilloscope.
    Older systems may use a throttle switch to provide control unit with idle or full load throttle position.
    Engine Rpm signal
    Verify signal received from the crankshaft position sensor during cranking and engine running. Most vehicles crank at around 200rpm when the starter is operated sensor output signal can be checked  using the 'live data' function of a scan tool depending on data refresh rate. Oscilloscope signal testing can further verify condition of crankshaft position sensor and toothed wheel .

    Camshaft Sensor

    The Camshaft position sensor is often used for cylinder identification on sequential fuel injection systems.
    The cam sensor signal may control the timing of injection.

    Battery voltage
    Check battery voltage. Switch on loads such as headlights / fan / heated rear window and check battery charging voltage is maintained.
    Coolant temperature sensor
    Verify the coolant temperature sensor reading as seen by the ecu when the engine is cold, during warm up, and at normal operating temperature. Coolant temp sensors are normally of negative temperature coefficient type , ie, resistance decreases as temperature increases, though some systems may use a ptc sensor.
    Intake air temperature
    Verify the intake air temperature sensor reading .Air density
    changes with temperature. Intake air temperature is used to correct fuel injection duration to aim for stoichiometric combustion (lambda 1 )  and greater fuel economy..
    Mass Air Flow sensor or Air mass meter
    Observe dynamic data to verify operation of the Mass Air Flow
    sensor at different engine rpm . Check airflow increases as the rpm increases. Air flow sensor response can be checked further using oscilloscope signal testing methods..
    Manifold Absolute Pressure
    Check the engine vacuum at closed / open throttle and when engine is under load. Problems with this sensor can be caused by blocked or split pipes.
    Boost pressure
    Check output boost pressure of the turbocharger, boost pressure sensor reading.
    Low boost pressure readings can be caused by a worn turbocharger,or wastegate stuck due to faulty control solenoids or vacuum circuit.
    Many engine management systems provide a 'desired boost pressure reading' and an 'actual boost pressure reading'.

    Lambda (Exhaust gas Oxygen) Sensor

    Check that the Lambda sensor switches from Rich to Lean and vice versa as the engine runs at normal operating temperature. Check milli-volts output using dynamic data display. Where lambda sensors are fitted before and after a catalytic converter, the first sensor will be correcting engine fuelling (expect a switching signal) and the post catalytic sensor should have a steady signal to indicate the catalytic convertor is working. Check data against manufacturers specification and further verify using oscilloscope signal testing.

    Feedback control

    Check engine management is in open loop control at cold start (monitor coolant temperature parameter )   and moves to closed loop (lambda sensor feedback to control engine fuelling via ecu)  status when at normal operating temperature.

    Injector duration

    Check opening time of injectors at cold start, during warmup, and at normal operating temperature

    The longer the injector opening time the more fuel being delivered.

    Fuel pump relay status

    Monitor whether fuel pump relay is on / off.
    A relay low voltage or open circuit fault may indicate a broken wire or relay coil fault. Ful pump relay operation on some manufacturers systems may be inhibited until the engine rotation signal is acquired by the control unit.

    EGR system status

    Exhaust gas recirculation control is designed to reduce the output of NOx in exhaust gasses by lowering engine combustion chamber temperature. EGR system faults often occur due to carbon build up causing restricted operation, incorrect feedback signal, and computer system to  activate a limp home or reduced power mode on detection of failure of this emission control related system.

    Typical engine management actuator & wiring test functions performed by the scan tool

    Fuel pump relay
    Turn on / off
    Idle air control valve
    Operate. Removal from the throttle body can allow carbon deposits to be cleaned from the IAC using solvent cleaner whilst operated by actuator test function.
    Stepper motor
    Activate stepper motor to verify operation and wiring continuity and motor / valve operation.
    Cooling fans
    Switch on / off low and high speed cooling fans to verify operation and wiring.
    Coil driver test
    Verify the operation of ignition coils by operating using test spark plugs

    Injector test

    Turn fuel injectors on / off to verify electrical operation. On some systems this function may be carried out whilst the engine is running to enable power balance testing and help identify faulty cylinders.

    Solenoid test

    Activate items such as Exhaust gas recirculation solenoid and
    canister purge valve solenoids to verify wiring and operation.

    Reset Service Interval

    Reset dash inspection and service lights. Reset service mileage countdown values.

    Routine Tune Up:

    This may include a scan tool test for stored fault codes. Just because the check engine light is not on does not mean there are no stored fault codes or malfunctions.
    A visual check of vacuum hoses ,wiring and spark plugs can also reveal maintenance required.
    Routine replacement of service items such as Air filter, Fuel filter, Spark plugs, may also bring benefits.

    Click here for more information about fuel injectors

    The table below is a rough guide to computerised engine control strategy. All values are approximate and will vary from vehicle to vehicle.

    Engine Cranking during cold start
    Coolant temperature below 20 degrees centigrade
    Rich fuel mixture achieved by opening injectors for longer duration
    System in open loop status using pre programmed fuel settings based on temperature and airflow
    Engine started and running in warm up phase
    Coolant temperature between approx 20 and 70 degrees centigrade.
    Alternatively mode may be based on a time value since engine start up.
    Injector duration maintained to provide a slightly rich mixture to prevent stalling
    System in open loop status with fuel delivery computed from
    mass air flow, temperature and manifold absolute pressure.
    Engine at operating temperature
    Coolant temperature above approximately 70 degrees centigrade
    Average injection duration reduced to provide a leaner mixture for fuel economy
    System switches from open loop control in to closed loop control mode. Change over can be a programmed function of coolant temperature and Exhaust gas Oxygen sensor (lambda sensor) voltage signal indicating a rich mixture status at least once.
    Exhaust gas Oxygen content is monitored (lambda sensor switches etc...)and signal feedback processed by ecu to adjust injection duration to acheive best combustion of air fuel mixture.
    Hard acceleration or heavy engine load
    Driver demand monitored at throttle position sensor.
    Engine load monitored at Manifold absolute pressure sensor.
    Injector duration increased to provide fuel enrichment .
    Engine produces more torque for acceleration.
    Engine control computer may switch into open loop control mode during acceleration.
    Throttle position sensor signal indicates reduced demand.Engine at normal opeating temperature.
    Air fuel ratio increased to reduce emissions of hydrocarbons and carbon monoxide. (Less fuel)
    Feedback control status may be in open or closed loop mode depending on program of engine controller.
    Engine idling
    Engine temperature normal.Throttle postion monitored or idle switch closed.
    Exhaust gas recirculation on to reduce emissions.
    Injection pulse width controlled by ecu to provide efficient fuelling, and idle air bypass controlled to maintain 800 to 900rpm and prevent stalling.
    Closed loop control status, Injection duration controlled based on input signals from exhaust gas lambda sensor.



    We welcome enquiries for Car  diagnostic testing in Shrewsbury , Telford, and surrounding area.