Autoelectrics tech pages

Autoelectrics Mobile Product Services. Shrewsbury Shropshire 07703 558610

Vehicle Electrics & Diagnostics

Vehicle computerised diagnostics Mobile service - car and van electrics repair in Shropshire
- Shrewsbury Telford and  local Shropshire areas.

Engine Management warning light on ? Breakdown ? 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 is a means of using the ability of the vehicle computer control system to monitor  the condition of  vehicle components.

A dashboard warning lamp illuminated can signal impending failure .We DO NOT recommend vehicle operation is continued with a warning lamp or warning message active - It is a warning for a reason !

First check your owners manual to find out what the warning light refers to. Operation sequence of most engine system related dashboard  warning lamps illuminate when the key is switched to ignition position and should go out when the vehicle engine is running.



Check engine lamp

Illumination of the 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 probably affecting exhaust gas emissions. Vehicles with diesel engines may also use the glow plug pre heat warning lamp to indicate engine management information.

Read / Delete Fault Codes

If a vehicle electronics system warning lamp eg the check engine warning light comes on during  engine operation  a fault code has almost certainly been logged by the engine control system, and consequently the control unit strategy  may revert to limp home or restricted mode as a safety feature.

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 where a deviation in actual and desired fuel pressure is present indicating leakage.

Limp home mode

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.

Potential ECM warning light on causes

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 map, etc)
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.

Retrieval of fault codes

Many vehicles require diagnostic equipment with dedicated software to interrogate the ecm for 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.

Fault Code Categories

EOBD fault codes

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:

Second digit of code refers to sgeneric type. Third digit of code refers to sub system