Knowledge Base

A "How To" guide to accessing the onboard diagnostics on the Mk1. Codes and images are included

The Check Engine Warning Light

The Warning light is located on the dashboard (image below) . When the ignition is switched on, the light should illuminate, as soon as the car is started however, the light should extinguish.

The Check Engine Light

If the light remains on, then the ECU has detected a fault that will need to be seen to.

In order to obtain the error codes, the following conditions have to be true
' Ensure you have a minimum of 11 Volts at the Battery
' TPS fully closed (Throttle Position Sensor)
' Car is in neutral if you have an automatic box
' All electrical items are switched off
' Engine is at normal running temperature

Switch the ignition on (Key position 2), but don't start the engine.

Grab a paper clip or similar short piece of wire; Insulated is best, as you don't want to short it against any bodywork. I prefer those coloured paperclips!

Now the diagnostics connector is bolted to the chassis, to the left next to a 'Resonator Box' (4A-GE illustration below) - thankfully its rather aptly labelled 'Diagnostics'! The location of the plug on 4A-GZE (supercharged) engines is near the intercooler.

Lift of the cap and you will probably be greeted with a load of gunky grease. This is correct! This is to stop water ingress.

Connect one end to Terminal T, and the other to E1. See the picture below to work out which is which. But there is also a diagram on the inside of the cap.

Output of Diagnostic Codes

The codes are outputted using a sort of 'Morse Code' system, pulsing the 'Check Engine' Light x number of times, then pausing, then moving to the next Code. The pause between codes 10 and over is represented by a 1.5 second pause. The pause between the codes is 2.5 seconds, and then a final 4.5second pause tells you its reached the end of the code. The ECU will then start the flashing process from the beginning again

Lets take an example:

Error Code 6 and 12 would be translated as

: Fri Dec 30, 2005 11:12 pm

Just read this article, good article but the error codes listed for the 4age are not correct for for UK cars with a MAP sensor (which is all of them, barring imports), they are for 4age engines with a MAF sensor. The correct codes for MAP sensor cars are listed on my website MK1 ECU codes

: Sat May 13, 2006 7:32 pm

Jimi your link doesn't work. I think you have typed in the address incorrectly.

Edit:
I think Jimi's (very detailed) link should be: Click_here_For_Mk1_Error_Codes

In case the link doesn't work here's my old list of UK mk1 MR2 error codes. I'm 'think' these are right:

1/ No error

2/ MAP Sensor or MAP Sensor Circuit (PIM)

3/ Failed Ignition Confirmation Signal From Ignitor (IGF) (IGT)

4/ Coolant (THW) Sensor out of range.

6/ Failed rpm (Ne) (G) signal to the ECU

7/ Throttle Position Sensor fault (TPS)

8/ Air temperature Sensor out of range (THA)

9/ Vehicle Speed Sensor Fault (SPD)

10/ No cranking signal (STA) during startup (car was bump started?)

11/ Failure of 'Throttle Open/Closed' switch (IDL)

Code 11 sometimes gets referred to as the AirCon sensor test. I think this operates another idle up valve on some overseas models. On the UK car I think it is just the throttle (closed) contact switch (IDL). You will probably get code 11 if you fit the diagnostic link wire whilst the throttle is pressed.
(because you are not meant to press the throttle when you fit the test link! The ECU diagnostics assume the 'throttle closed' switch has failed, when in reality it's because you have been pressing the throttle!)

: Sat May 13, 2006 8:14 pm

Cheers Jeremy
I forgot I'd rewritten the article in html, so the url had changed, I've sorted the link in my previous post. I've checked the codes you've listed against the ones I have and they are the same, just slightly different descriptions, good to have independent confirmation.
Jimi

: Thu May 18, 2006 2:40 am

Good one