Thread: OBD2 -> OBD1 stepdown harness diagram

that sounds more like an ignition problem than a harness problem..

Yes, but i get the harness out and put the OBD2 ECU and it works normaly...

The ECU continues to be on, y saw a little red led inside the ECU that does not turn off... unless I disconect the ECU from the harness.. with the OBD2 i dont have that problem.

Your best bet may be to inspect for loose wires. The diagram is on the 1st page some you can check everythings correct location. Curious who made your stepdown they may be able to help you out.

Yesterday i took the time to review my Stepdown harness... i have some cables that just need solder, and other ones that definitively are cut from the plug...

Also i found that i dont have the consult cables conected...

Is this ok? i think i can do something to fix the cables...

OBDI
(1). Rx (pin 7)
(2). Tx (pin 15)
(3). CLK (pin 14)
(4). 12V Ign (pin 38/47)
(5). GND (pin 39/48)
(6). CHK (pin 23?)

OBDII
(1). Rx (pin 64)
(2). Tx (pin 65)
(3). CLK (pin 68)
(4). 12V Ign (pin 56/61)
(5). GND (pin 10/43)
(6). CHK (pin ?)

Ok, today i solder the 2 cables that where disconected... those where:
OBD1 - 36 to OBD2 - 38 - this is suposed to be ignition switch.

OBD1 - 109 to OBD2 - 113 - This is supposed to be Current Return.

Now i put the ECU in the Car.. and then when i turned the car on i had the same problem... i couldnt turn the Car off even if i get the ignition OFF...

Then i cut the cable for the ignition switch... and problem solved... the car turns on and off normaly... but ... im having this problem...

Now the red led inside the ECU stays on when i turn the car off... ahd im afraid this would let my batery without power to turn the car on...

Anyone knows why the ECU's led is on?

Please help!!!

i need a step down harness can somebody help me please?

how up to date is this diagram, any new pins ect

Yes Nissan added new pins to your harness after this post was made

now would a obd1 automatic ecu be the same as a manual? wouldnt the difference be in the tranny module itself?

ECU's are different too. They have different tunes too. Auto is very limited market, thus your going to have a lot of manual labor on your hands.

Wiring it self, I've been starring at FSM's for last couple days, it doesn't seem to make any distinctions.