ive just bought a subaru impreza wrx 1992 k reg saloon,when you start it up the engine check light stays on for about 4 miles before going out,previous owner says it needs a service could this be the reason why its on? also where the hell is the diagnostic socket?? ive searched and searched and cant find it.many thanks in advance.

 

To check it you will need a 'Select Monitor' I think the port is under the driver side dash or you can check here www.JollyGreenMonster.com - Engine management specialist on the help page on how to check for error codes.

It doesn't come on because it needs a service it comes on becasue it's registered a fault.

 

thank you very much for that info.....just did the test and its telling me the KNOCK SENSOR is at fault...where is it and what does it do? many thanks.

 

the knock sensor picks up detination/knock and sends a signal to the ecu to pull timing out if you are a running poor grade fuel etc.....

it is located under the inlet manifold, its a black round sensor with 2 wires comming from it and has a bolt through the middle of it.

 

Most probably needs replacing.

 

I have just replaced mine on my 95 classic and it was not too bad to fit, a little fidderly when putting the bolt back in, I got mine off ebay for £22 quid and once in I reset the ecu and now the car runs a dream

 

If the knock sensor is detecting knock surely thats a fault to investigate ? its not saying youre sensor is faulty and to replace it , its doing a job in telling you theres det/knock detected !

 

not true, the knock sensor will not light a cel if it is detecting knock, it will simply instruct the ecu to retard the timing until no knock is detected.
The reason the cel is on is because it is sending info to the ecu and that info is out of range hence the cel.