Vehicle computerised diagnostics Mobile service -
car and van electrics repair in Shropshire
- Shrewsbury Telford and local Shropshire areas.
Engine Management warning light on ? Breakdown ? Engine Misfire ? Driveability problems ? Immobilised? Engine Management fault? Electrical fault - Car won't start ? repairs? Private Customers, Fleet & Motor trade Welcome. Unsure if you should drive the vehicle with a dash warning light on - We provide a mobile service that comes to you.
Computerised vehicle diagnostics
Dashboard warning lamps illuminated can have numerous causes warning of impending breakdown. We DO NOT recommend vehicle operation is continued with a warning lamp or warning message active - It is a warning for a reason ! Illumination of dash warning lamps indicating a malfunction may also result in MOT test advisory notice or failure (further guidance can be found in the DVSA MoT inspection manuals.
Firstly check the vehicle owners manual to identify the warning light function. Most vehicle system instrument panel warning lamps illuminate when the key is switched to ignition position as a self check is carried out, then should go off when the vehicle engine is running.
Check Engine or engine management warning ( MIL ) lamp indicates that the vehicle engine management computer (ECU , ECM ,PCM) control module has identified a fault related to the efficient running of the engine and possibly affecting exhaust gas emissions. Vehicles with diesel engines may also use the glow plug pre heat warning lamp to indicate engine management information.
If the engine management warning lamp or check engine warning light, illuminates during engine operation then a fault code has almost certainly been logged by the engine control system. Fault detection may cause the engine control unit strategy to reduce engine power output by reverting to limp home or restricted mode as a safety feature to protect the engine.
Sensor Inputs : The value expected from each engine sensor is programmed into the
software of the engine control module and represented as a map or lookup table. (Fuel map, Ignition
An out of range value may represent a faulty component , wiring circuit or mechanical condition.
The check engine lamp may illuminate to notify the driver that a fault has been detected for example when a value exceeds parameters programmed in to engine controller memory map.
Conrol Unit Software Safety Features
Logged faults may in some cases prevent functionality, eg the engine could be stopped from running by intelligent software function when a fault code has been logged.
Modern diesel engines fitted with common rail fuel systems which operate at very high fuel injection pressures may log a fault code when a deviation in actual and desired fuel pressure is present indicating potential fuel leakage.
Limp home mode will usually be noticed by the driver because of poor acceleration, shuddering, restricted performance, or the engine will not rev above a certain rpm.
Many vehicles require computerised diagnostic equipment with dedicated software to interrogate electronic system control modules and retrieve stored fault codes.
Automotive system electrical diagnostics involves an interrogation scan of the vehicle computer for stored fault codes using suitable diagnostic equipment such as a scan tool fault code reader.
Some older vehicles (usually Japanese) have a self diagnosis function allowing the the fault code to be read by counting the flashes of the check engine light and looking up the value in a reference table. Commercial vehicles, Construction and Agricultural machines may display fault codes on a diagnostic screen but require engineer user code to access.
Intermittent faults which occur during driving may be logged as an error fault code which causes the dashboard warning light to illuminate.
Avoid trial and error random disconnecting of electrical connectors in the engine bay during engine operation. Trial and error component disconnection may cause fault codes to be logged in control unit memory then requiring diagnostic equipment plug in to clear false fault codes. Once the ecm has logged certain fault codes this may prevent engine starting or cause erratic running.
Warning : Disconnection of piezo type diesel fuel injectors whilst the engine is running can be dangerous and introduce further problems such as leaving the injector open causing fuel build up in combustion chamber and potential hydraulic damage.
The term EOBD refers to European On Board Diagnostics and derived from OBD2. OBD2 trouble codes consist of a five digit alphanumeric identifier. The first letter identifies the control unit type setting the code:
for example a P0100 fault code would relate to a fuel or air flow fault which could be identified as a faulty air flow sensor or could be wrong of flow of air past a good sensor for whatever reason.
EOBD standards apply to Petrol vehicles from May 2001 >, and Diesel vehicles from 2003>. EOBD Fault codes , sometimes referred to as P.... codes are generally logged for factors which affect vehicle exhaust emissions. EOBD monitoring has various modes including Freeze frame Data, which can be useful to help diagnostics.Vehicle Manufacturer specific fault codes
Specific fault codes relating to in depth component functions may not covered by EOBD
Diagnostic equipment will reset the control system computer software and often turn the warning light off , however if a fault is still present the check light will often illuminate again once a driving cycle has been completed unlessthe fault has been rectified. In some cases several error codes may be present.
Following testing, a faulty wiring circuit may be repaired or component adjusted , cleaned or replaced.
This may occur where a fault or glitch happens too fast for the control unit software to register. Best explained by imagining a photographer taking pictures of a racing car going around a track at high speed, if the shutter speed on the camera is set incorrect or photographer too slow,the car may pass by without any picture being taken. The same thing can happen with sensor faults. This scenario may involve oscilloscope data logging the vehicle during operation hoping that the fault will occur and can become time consuming and expensive.
Our diagnostic equipment is capable of
Following repair work the fault code memory of the vehicle computer may need to be reset to clear stored fault codes.
Electronic Engine Management Engine control computer module compares values from various sensors to calculate;
( EGR ) system functions to reduce combustion temperature and oxides of Nitrogen ( Note : not Nitrous oxide !) EGR and Idle speed control ( ISC ) devices are particularly prone to failure due to build up of carbon and soot deposits which can restrict the air inlet system of the engine.
EGR systems may cause the MIL warning lamp to illuminate intermittently and flag a P0400 EOBD fault code due to "critical system malfunction" as described on certain diagnostic equipment !
Exhaust additive systems introduce chemicals in to the exhaust system to reduce diesel soot emissions. Many of the additives are Urea based and corrosive. Typical faults include damage to wiring from leaking additive.
Cam position sensor : used to identify cylinder phasing
Crankshaft (CKP)position sensor : Identification of engine crankshaft position and calculation of engine speed and combustion forces. Frequency and amplitude signal is proportional to engine rotational speed.
Symptoms: Non Start, Misfire
Typical failure : Signal errors can occur due to sensor failure , phonic wheel damage, wiring connection failure, loss of synchronisation between crankshaft and camshaft(s).
Throttle position sensor (TPS)
/ Accelerator Position sensor (APP)
function:Driver demand signal. TPS failure may occur due to wear of potentiometer track causing flat spots and hesitation when accelerating.
Brake Pedal Position & Clutch Pedal Position sensors used to reduce to stabilise idle speed and fuel delivery quantity when engine is off load . Faults may occur due to worn out switches resulting in false (implausible) signals.
Mass Air Flow (MAF) sensor measures volume of air entering air intake , Air Mass Meter measures weight of air entering intake tract. Engine load sensor which can effect fuel metering (petrol engine) or EGR position (diesel engines) .
Intake Air Temperature Sensor may be incorporated with air mass meter , with MAP sensor (T-MAP) or seperate.
Manifold Absolute Pressure (MAP) sensor measures engine load by vacuum (petrol engines) or boost pressure (turbocharged engines) at intake manifold. Split or blocked pipes can effect operation. MAP signal can influence fuel control, EGR, and turbo boost.
Temperature measurements may be signalled by either coolant temperature sensor or cylinder head temperature sensor. Temperature signal is processed to compensate engine smooth running by control of fuel delivery egr position, & diesel pre heat function.
Fuel Delivery System : Low and high pressure fuel injection pumps, pressure regulator, fuel injectors. Prone to faults caused by fuel contamination , and general wear.
Boost pressure control : turbocharger waste gate position and hence boost pressure control is often actuated by solenoids controlling vacuum circuits. Common faults can include loss of vacuum due to vacuum pump wear, split or blocked vacuum pipes, electrical circuit faults with control, solenoid or wiring.
Lambda Sensor (as fitted
to Petrol & Gas
Measures oxygen content of exhaust gas and is used as a feedback signal to control fuel quantity delivery. Can deteriorate due to age and contamination. Lambda sensor fault codes may also relate to problems other than the sensor itself. Lambda sensor operation can is affected by sensor temperature .Lambda sensor feedback signal is only used when engine operating temperature is sufficient to enable closed loop control status.
A second lambda sensor may be fitted in the exhaust system after the catalytic convertor to monitor condition of the catalyst.
We can supply a range of replacement sensors and actuators at competitive prices
This may flash as the engine is cranked whilst the immobiliser is active.
Manufacturer or OEM immobiliser systems are often integrated into a vehicle on board computer system and may prevent starting, ignition, or fuelling circuits from operating.
Faults can sometimes occur if a receiver does not recognise the signal transmitted by a coded key or remote, or no transmission due to defective remote/discharged battery, or broken wiring causing CAN signal faults.
This type of system can rarely be bypassed other than by reprogramming.
Aftermarket alarm and immobiliser systems are installed as an added security measure by some owners. If these systems fail they can normally be removed or bypassed by an autoelectrician to enable vehicle operation.
You should check with your
insurance company if an aftermarket alarm is to be removed as this may affect insurance policy validation.
There is more information about alarms & immobilisers on our vehicle security page.
Manufacturer Systems include : Ford,Bosch, Sagem, Renix, Delco, Denso, Autoliv, Lucas,
Vehicle System function diagnostics for :
Common Rail Diesel, Engine Management, Petrol Fuel Injection,Diesel Fuel Injection including Lucas EPIC,Spark Ignition, Antilock Braking system (ABS), Airbag,Adaptive damping,Air conditioning, climate control,Audio control,Cellphone, Central door locking,Diesel pump electronics,Immobiliser,Insrument cluster, Dashboard,Lighting control, CANbus,Passive Antitheft PATS,Power doors, Steering Control, Electrically operated power steering, parking sensors, tyre pressure monitoring control, ECU information & coding. DPF regeneration.
Breakdown callout and diagnostics in Shrewsbury, Telford ,Shropshire areas.
Charge warning light on indicates that either battery voltage is out of range or that the alternator is not generating current to recharge the battery.
Low battery voltage can be caused by a faulty battery, faulty alternator / dynamo, loose / broken drive belt or a wiring fault.
Incorrect battery reference voltage levels may affect engine management, and other electronic control systems.
Our mobile service can verify the condition of your vehicle battery using either midtronics or Bosch battery tester, or check for alternator output, diode condition ,and trace wiring faults which may be causing the alternator not to charge or the battery voltage to drop.
Systems on late model vehicles are often computer controlled and sensitive to battery voltage levels which may set a fault code requiring dedicated test equipment to reset.
We can supply an extensive range of alternators starter
motors and components and also provide
unit repair and recondition facilities
We have a bench test facility to free run bench test your alternator.
(Also known as SRS, Supplementary Restraint System, etc)
An Airbag warning light which stays on is an MoT test fail. SRS Warning Illuminates if a fault is recognised by the airbag control module. Airbag deployment is controlled by sensors which react to impact above 20mph. The SRS system self checks for wiring, sensor ,and actuator faults which may cause false triggering. If such a fault occur the system normally disables and illuminates the airbag failure warning lamp.
Faults causing illumination of the airbag warning light can occur due to wiring, connections, impact sensors, control module faults, igniter defective, spiral cable defective, abnormal system voltage.
Airbag systems have a self diagnosis function which logs fault codes when an error occurs and may then be diagnosed by interrogation procedure with suitable diagnostic equipment. In the event of a crash, airbags may be deployed to protect occupants. Airbag deployment will often cause crash data to be stored in the airbag module. Please not we do not clear crash data or repair airbag control modules for liability reasons. We do have facilities for retrieval and clearing airbag system fault codes.
illumination of oil pressure warning lamp indicates low engine oil pressure which may lead to major mechanical failure ie engine seizure and breakdown. Possible causes: Low engine oil level, oil pressure switch or circuit fault, Oil pump failure, Oil pressure relief valve fault.
Certain vehicles are fitted with a low engine oil warning lamp and level sensor in the engine sump.
Low coolant level. Check for leaks as engine damage may occur due to loss of coolant. A low coolant level warning lamp may also illuminate if the wiring is chaffed and shorted to ground or the level sensor is faulty.
Indicates a problem with the engine cooling system which may cause engine damage. Possibilities are ; blocked radiator , faulty pressure cap, coolant leaks, combustion gas leak into cooling system, cooling fans not operatng due to motor ,switch,or wiring defects.
Antilock braking operates by rapidly applying, and releasing the brake on each wheel just before it locks. Faults within the Antilock braking system may cause the ABS light to illuminate. When the ABS system logs a fault this often causes the ABS to be disabled with affects on braking and steering control requiring increased pedal pressure as the system reverts to failsafe mode. A permanently illuminated ABS warning lamp will result in MoT test failure as it represents a dangerous condition. Typical reasons for ABS light illumination are ; faulty wheel speed sensors, damaged or dirty rotor sensor ring, faulty modulator solenoids, abnormal battery voltage, system pressure faults, wiring faults. Fault code reading using diagnostic equipment, possibly followed by individual component oscilloscope signal testing or wiring checks then repair.
Brake fluid level warning lamp takes its signal from brake fluid level reservoir. Illumination may indicate loss of brake hydraulic fluid or wiring or sensor failure.
Check condition of brake pads or shoes. Faults in wiring circuit may also cause brake sensor warning lamp to illuminate.
Steering electronics often require recalibration of steering angle sensor after battery disconnection or replacement.
Automotive diagnostics involves more than plugging in a scan tool to read faults.
Computer diagnostic error codes only provide a clue as to what the control system recognises as a fault but remember it is an electro mechanical system which is under repair. Training providers often refer to "Cause" and "Effect" when lecturing on automotive diagnostics.
Motor trade experience combined with continuing professional development of staff through system manufacturer training courses aids vehicle system diagnosis & repair.
The Controller Area Bus Network or CAN network allows data communicaton between various computer modules fitted to a vehicle. CAN faults may include broken wiring. Configuration of modules on a CAN network can lead to faults with one module affecting other modules which may also be used as a diagnostic feature where computers or control units are monitored as part of the network.
Extensive use of vehicle diagnostic equipment in the course of business has enabled us to gain links with reputable suppliers of vehicle diagnostic equipment for Car Van Truck and Agricultural equipment markets. If you are a trade customer looking to purchase such equipment please feel free to enquire.
Professional level diagnostic equipment is often expensive and cost of such equipment can easily run into several thousands of pounds. If purchasing diagnostic equipment we recommend reviewing not only initial purchase price but also the ongoing cost of software updates to enable operation on modern vehicles and also facilities for the provision of technical information such as wiring diagrams , component locations, and coding information.
Automotive Diagnostics supplied to * Private Customers * Motor Traders and Garages * HGV and Light Commercial vans * Road Haulage Fleets * Passenger Transport Taxi Bus