mxexux

So I need help from somebody that has done a "proper" auto to 5 speed swap in an S14.

My problem is that I keep getting a P0705 DTC code (which is transmission range sensor circuit malfunction). I am trying to smog the car, but this code is keeping me from it.

Car info and history:
It is a 1998 that was originally auto. The guy I bought it from claimed that he did the swap properly with no CEL. Well it did pass smog the first time without issue. For the past couple years, the car would occasionally throw a CEL for the neutral switch, but clearing made it go away for a few months and I didn't think anything of it.

Now its time for another smog check, but the code comes back after a few days. I look into it and find that none of the tranny sensors are hooked up(thanks previous owner), also the neutral switch was bad and I had to replace it with a new one. I go through and finish the wiring side of the 5 speed swap according to KA24DEdevelopment. Clear the codes, but the P0705 comes back again after a few days! Verified that the ECU appears to be a manual one (J6 A18-H63 GA3).

Running out of ideas here. Only other thing I can think of is that the previous owner removed the TCM. While researching the 5 speed swap, I didn't see any mention about removing it. I am wondering if its absence may be causing the code somehow.

Sorry for the long post buy any input would be greatly appreciated.

yzrider450f

During my 5spd swap on my '98 the CEL came on once I unplugged my TCM, but i still have the auto ecu.

My question is why did it go long without throwing a code before? Seems odd..

mxexux

Well for the last couple years it would throw a code for the neutral switch(P1706), but it would only do it around every 5 months or so. This last time, I let it go for several months thinking that it was just the neutral code again and didn't worry about it. Then I realized that I need to smog it so I just cleared it again and drove it over to the smog place. The smog guys says he can't smog it because all the monitors are incomplete (D'oh!, forgot about that). I drive it around some to clear the monitors, but it now throws code P0705.

After fixing all the wiring and clearing the code, I drive it around to clear the monitors, but it throws the code again just before clearing the last two monitors (AAARRRGGG!).

kruked

Take it a block from the smog depo, clear the codes, take it to smog depo, wah bam!

Idk, we don't have smog in FL so I don't know if that'll work for you or not.

__________________
I like my bikes how I like my b¡tches...naked!
2014 Triumph Street Triple

JM216S14

mxexux

Once again...thanks Florida -_-

kruked

Never mind

__________________
I like my bikes how I like my b¡tches...naked!
2014 Triumph Street Triple

Ilya

If there was only a written procedure for how to diagnose such a code.
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.
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Oh wait....there is!!!!!!! It's called a 1998 Nissan 240sx FSM. Use your mouse to navigate to the EC section and look on page EC-231. There will be pictures to hold your hand while you go through the hardships of troubleshooting a 17 year old car.

Automatic cars come with an additional Computer to control the transmission. This computer is also connected to the ECU. So when you plug in a manual ECU, it may get confused.

Ilya

When your mind is blow and you give up because your brain is confused, look at the AT section on page AT-14. It shows the TCU pin 13 is directly connected to pin 22 of the auto ECU. However, on a manual ECU that pin is directly connected to the neutral position switch(EC section page EC-9)

So I don't know what kind of rats nest your car is in but your job now is to figure out how your car is connected. There will not be a magical post that tell you exactly what to do to fix it. You will need to get your hands dirty

Ilya

EC-408 is the page to look at. I apologize for the confusion.

mxexux

Well Ilya, you gave a good effort... in trying to act hard. lol

But, if you had any reading comprehension you would have actually read my posts in their entirety and seen that I have replaced the neutral sensor and personally wired it to pin 22 of the ECU. You would have also read that my TCM is not present.

My question still stands. Will the absence of the TCM somehow cause a manual ECU connected to an auto harness to throw a P0705 code?

Surely, in this ocean of Zilvia idiots there must be someone who knows what they are talking about and can shed some light.

Ilya

A couple of things:

1. Are you sure you have a manual ECU from a 97-98 S14? You can reference the nissan part number here: http://jimwolftechnology.com/wolfpdf/ecu-id.pdf

2. You need to double check the wiring of the Neutral and 5th gear sensors and verify the sensors work as designed. I know I had the issue of someone using a 4th gear switch in place of a neutral switch which has the opposite effect (My s13). Neutral switch is closed when in neutral AKA continuity, and open when in another gear aka no continuity. Check the resistance of the switch at all possible gear too.

Pin 22 -> Nuetral switch -> GND
Pin 7 -> 5th Gear Switch -> GND

3. You still have at least 4 pins connected to an ECU that is not designed to have those pins connected. PINs 24, 29, 30, and 31 of the ECU.Those pins are now connected to a long wire which acts as an antenna especially in a environment like a car. So now you have a signal on those pins that should not be there. Try two things: reconnect the TCM or connect pins to ground through the old TCM connector. Maybe some of the pins need to be set high or low, but that is something that I do not know.

mxexux

Hmmm. Yes I am about 80% sure the ECU is a manual from a '97. The Jimwolf reference does not list the ECU I have; it also states that that list is incomplete and may be inaccurate so it must be taken with a grain of salt.

I double checked that wiring today even though I wired both the sensors myself. I verified that 5v is switching on and off to the ECU pins 22 and 7 as the respective gears are switched.

About the TCM, that is a good point about there being other connections going from the TCM to the ECU, but I have no idea how those would have an effect on the issue I am having. I will see if I can look further into it. I can't hook up the TCM again because it is absent since I have owned the car.

One thing I noticed was that 2 of the emission monitors were not clearing even though I had been driving around for several days. I happened to have a spare '97 ECU from a previous car so I installed it today. If the monitors clear without a CEL I will know that it was the problem which would be the first time I have ever heard of an ECU failing all by itself, but anything is possible right?

Ilya

Maybe you have seen this link, maybe not: http://jimwolftechnology.com/wolfpdf...WIRE%20MOD.PDF

As far as the pins connected to the ecu go, we are not sure the differences between a manual and an auto ecu and how those pins are terminated inside. Maybe the Manual ECU expects pin 29 and 30 to be ground yet it sees a varying voltage from the antenna effect of the wires hooked up, and that may throw things in for a loop.

Measure the voltages at the TCU connector of the pins that have wires connected to the ECU.

If none have a voltage while the car is running, ground them.


Also another thing could be a faulty Neutral Switch. It is possible that it no longer keeps the contacts open while you go through gears. For example, as you switch from 4th to 5th gear, the Neutral switch makes contact at the same time the 5th gear switch makes contact so the ECU goes "he is in 5th gear and neutral, I GIVE UP".

Id almost short out the Neutral switch with a piece of wire and see what happens. and I would do the same for the 5th gear switch.