# Note to anyone with undiagnosed 240SX problems



## dead1486 (Aug 25, 2005)

Struggling with and undiagnosed problem myself I thought I should tell everyone the biggest time saver in the world...

My 93 240 was running poorly and I had already replaced numerous parts and was extremely frustrated when I heard about the greatest thing in the world.. The ECU Self Diagnostic mode.. The ECU is located on the passenger side of the car just left of the door behind a removal panel. To access it you must remove the sill from the doorway (held in by several plastic screw clips) and pull the little panel which goes from the sill up to the dash. Behind this panel you will see a metal box with 86 in large letters on the side (possibly only a 91-94 240SX thing). There are 2 bolts holding the ECU to the side of the car (one above and one below) which take a large phillips head screwdriver to remove. Once these are removed you will have to carefully jiggle the ECU out of its mounting area and turn the side facing the engine bay towards you. You will then see a single flathead screw which is underneath a hole with a red LED inside it. Turn your key to the on position (all dummy lights on dash should be on) then proceed to turn the flathead screw (dont force it if it stops) fully clockwise. Wait 3 seconds! Turn the screw back counterclockwise til it stops and look at your check engine light. 

It should flash a code to you, for instance 
blink......blink......blink......blink..blink..blink would be 33 
(the slower blinks being the first number and the faster blinks being the second)
note: If there are 2 distinct numbers that means you have 2 seperate codes

Also note that your check engine light does not need to be on while you drive for you to have an error being reported to your ECU.

The code meanings can be obtained here http://www.emergent.com.au/200sx/ecucodes.html

Don't Forget Your 240SX Is Your Friend And Will Tell You What's Wrong If You Ask It  

This is strictly for OBD-I cars (before 1995) it may or may not work on post 95 models although I have no way of checking on that.

Thanks to anyone who reads this and I hope it helps you as much as it helped me. After all, who says you need to pay someone 50 bucks to tell you what you can find out yourself.


----------



## afroeman (Oct 12, 2004)

dead1486 said:


> Struggling with and undiagnosed problem myself I thought I should tell everyone the biggest time saver in the world...
> 
> My 93 240 was running poorly and I had already replaced numerous parts and was extremely frustrated when I heard about the greatest thing in the world.. The ECU Self Diagnostic mode.. The ECU is located on the passenger side of the car just left of the door behind a removal panel. To access it you must remove the sill from the doorway (held in by several plastic screw clips) and pull the little panel which goes from the sill up to the dash. Behind this panel you will see a metal box with 86 in large letters on the side (possibly only a 91-94 240SX thing). There are 2 bolts holding the ECU to the side of the car (one above and one below) which take a large phillips head screwdriver to remove. Once these are removed you will have to carefully jiggle the ECU out of its mounting area and turn the side facing the engine bay towards you. You will then see a single flathead screw which is underneath a hole with a red LED inside it. Turn your key to the on position (all dummy lights on dash should be on) then proceed to turn the flathead screw (dont force it if it stops) fully clockwise. Wait 3 seconds! Turn the screw back counterclockwise til it stops and look at your check engine light.
> 
> ...


THAT is freakin sweet. This is something I have never known about the 240's before. Thanks bro.


----------



## dead1486 (Aug 25, 2005)

afroeman said:


> THAT is freakin sweet. This is something I have never known about the 240's before. Thanks bro.


No prob man I thought so too!


----------



## dead1486 (Aug 25, 2005)

Please make this post a sticky! It will help everybody out by giving them an easy way to find out what that mystery noise is or what that jolt is when the throttle is opened up..


----------



## Polah Bear (Jul 18, 2005)

dead1486 said:


> Please make this post a sticky! It will help everybody out by giving them an easy way to find out what that mystery noise is or what that jolt is when the throttle is opened up..


Great thread!!

Thanks for the info! Much appreciated....


----------



## 240sxs1377 (Jan 9, 2005)

good info im going to have to check that out tommorow.


----------



## 240on430 (May 3, 2005)

"Also note that your check engine light does not need to be on while you drive for you to have an error being reported to your ECU."

sure about that?


----------



## dead1486 (Aug 25, 2005)

yeah I'm pretty sure, I mean my 93 240 convertible showed me 2 error messages, TPS and O2 Sensor Circuit and the engine light remained off. I disconnected the TPS to increase driveability and still my check engine light remains off if you dont believe me try it yourself.


----------



## bluuuurr (Sep 13, 2005)

awesome info man.. I've been dying to check why my CEL comes on and off randomly..


----------



## 240on430 (May 3, 2005)

ok, cool. thanks for the reply.

i'll go ahead and run a test. im hoping for 55!


----------



## 240sxs1377 (Jan 9, 2005)

bump for great info.


----------

