# ECU: How to Read and Diagnose Z31 Codes: 84-86 ONLY



## asleepz (Feb 24, 2004)

Since the last thread we had about this was a little iffy. Here's what the FSM says... If anyone needs a reference page posted please ask through PMs. All pictures are under 70KB a piece for you 56K users. I compressed them quite a bit.

Procedure to pull codes is as follows.


----------



## Zen31ZR (Mar 24, 2004)

Owned by the :redx:


----------



## asleepz (Feb 24, 2004)

Sorry man but I see them all... the first 4 are attachements straight off the board. The last one is photobucket and they all work..


If anybody else is having problems please post.


----------



## Zen31ZR (Mar 24, 2004)

Fixed.  Can everyone see them?


----------



## bALISDIGK (Jan 30, 2005)

This seems to be the early ecu code reading procedure (THE TITLE SAYS 84-89). It is not the one used on 87 or later ecus. There are differences in codes also.


----------



## asleepz (Feb 24, 2004)

Well that's what the FACTORY SERVICE MANUAL says. So I think it's probably correct.


----------



## bALISDIGK (Jan 30, 2005)

Well I have worked on 1987 Maximas, 1988 300zx, 1987 200sxse and I assure you that it is not the correct procedure.

I have also worked on 1984/1985/1986 300zx.

Dropping codes on 87 and later vg30e Nissans is only done in mode 3. Unless the procedure tells the person HOW to even get to mode 3, then it is not correct.

The procedure you list is from a two mode only type ecu.


----------



## asleepz (Feb 24, 2004)

Well I've pulled the codes from mine this way and it worked perfectly...


----------



## bALISDIGK (Jan 30, 2005)

That procedure is from a 1986 Field Service Manual.

Its possible that your ecu is from a 1984-1986 car. Just drop it and if there are codes listed on the ecu box itself, then it is a 1984-1986.

If it does not have codes listed on the outside, its a 1987-1989 ecu. I take it you are not the origional owner.

Its very doubtful that Nissan would move Maximas, 200sxse and non-turbo 300zx to a new generation ecu and leave the 300zxt with an older technology.


----------



## bALISDIGK (Jan 30, 2005)

a18 680 m90 IS A 1987 300ZX TURBO part number for a 5 speed federal (non-Cali) Nissan ecu.


----------



## Zen31ZR (Mar 24, 2004)

Possible maybe somehow he was putting it in Mode 3 accidently. From what I saw of the mode change procedure in my 88 FSM, it's possible, but you'd have to get real lucky......

I'll change the title to reflect the earlier procedure. 

I can also either make a seperate thread for the 87-89 procedure , or refer people to the FSM link, the section explaining all 5 modes and code retreival and testing procedures for the parts involved is incredibly long. Thanks for bringing this to our attention, BTW.


----------



## asleepz (Feb 24, 2004)

Hmm that's something I would have to check out. No I'm not the first owner but the first owner wouldn't know how to change out an ECU. Maybe I was just lucky and it gave out the codes either way. I'll have to give it some more investigation.


----------



## bellcrew (Nov 19, 2009)

hey my ecu doesnt light up the leds.... does that mean i need a new one? i am getting battery voltage


----------



## stennu76 (Sep 18, 2010)

Sorri,maybe it's a dumb question but where can i find this part,where I can do self-diagnostic? Under the hood?near the engine?


----------



## AZ-ZBum (Nov 21, 2004)

For most countries, the ECU is in the passenger side kick panel.


----------



## smj999smj (Jan 1, 2006)

Troublcodes.net Trouble Codes OBD & OBD2 Trouble Codes and Technical info & Tool Store. By BAT Auto Technical


----------



## stennu76 (Sep 18, 2010)

Can somebody read the code for my, I don't understand how?


----------



## smj999smj (Jan 1, 2006)

It's not flashing codes, but modes. There are 5 modes; mode #3 is self-diagnosis. There should be a screw on the ECM which you can turn to enter the mode. When you enter the mode, the red and green lights will flash seperately to identify the code. IE, a code "32" would flash the red light three times and the green light twice.


----------



## stennu76 (Sep 18, 2010)

I think now I did everything right and the codes are 22,21,41?

And they mean:

21-ignition signal missing in primary coil
22-fuel pump circuit
41-fuel temperature sensor circuit






Problem of my car is that it hasen't got the power it used to have and when accelerating it just jumps on the first gear but when the rpm's go up, the acceleration gets better and when the car is on neutral,it woun't work evenly and the rpm's go up and down 900-1700. (my car: nissan 300zx z31non turbo1985)


----------



## stennu76 (Sep 18, 2010)

Did I do everything right? and what do these codes mean,what should I check and how? can somebody help me please?


----------

