I thought pin 71 was the P and N selector, which is already grounded on the TT harness?
I am going to resurrect this thread, because I have a JDM ATX converted to TT, using a '97 JDM TT ECU (all JDM ECUs are three plug). I TT-d my car at least one year ago and had the pin #71 grounded as per BigTyla's instructions and my car was running fine, but when I logged my car, I did notice that the logs showed wrong readings on the shift stick position. Today, I plugged my SAFC2, using a Boomslang harness adaptor and the car wouldn't run properly until I plugged the two ends of the pin #71 together and it worked fine, but I also tried the one from the ECU grounded and the other one capped and that still worked. So, it works both ways. I am not sure how to find out if the timing was erratic when I had the pin #71 wire attached to the ECU, but the car definitely felt like it was running normal.
I drove the car and it ran perfect. No pins were shorted, so I decided to look into the ECU pinouts to find out why that is so if BigTyla had stressed that pin #71 must be cut. When I looked at the diagram on Stealth316, I saw that pin #71 is not "starter relay signal," but "inhibitor switch" (ignition switch: ON; selector lever set to P or N; selector lever set to D, 2, L, or R). I am not sure exactly where BigTyla got the pin #71 assignment as "starter relay signal" (Okay, I foind the source! It is an Excel file, listing all the ECU pinouts on Stealth 316. I have a link for it, posted further down. I think it is wrong though.)... He did mention that this assignment is for 1st gen ECU and I am running a 2nd gen JDM ECU on a 2nd gen JDM N/A car, but wouldn't that be true for all years JDM ECUs since they are all three plug? Anyway, I though that was strange and wouldn't mind getting some opinions on it... Also, I thought that it would be of help to others who might do this mod in the future. In the end, I still used the advice of BigTyla and grounded the ECU part of the wire of pin #71, just in case he was right. I wouldn't want to short my JDM TT ECU and having to find another one... However, I am going to check if the log will start reading properly the position of the shift lever when the pin #71 wire ends are connected to one another.
After driving the car today with pin #71 grounded on the ECU side and capped on the other side, I got a check engine light. Also, I noticed that the SAFC2 did not read the throttle value. After re-plugging both ends of pin #71 together, the check engine light went away and the throttle reading on the SAFC2 came back. That is somewhat awkward, because I have been driving with pin #71 grounded on the ECU side and capped on the other, for over a year now and I had no check engine light on... However, after plugging in the SAFC2, things changed.
I guess the SAFC could be changing things somehow, even though I can't understand how. Either that, or the fact that my car is a 2nd gen. JDM N/A with a 2nd gen. JDM TT ECU, changes things and the wire of pin #71 can be safely left alone without any modification. I don't understand why that would be the case, since all JDM cars use a three-plug style ECUs, which should in theory be the same as the 1st gen. USDM ECUs (except for the difference in the crank & cam angle sensor readings and the fans between the different generations), but who knows... So, as of today, I am keeping pin #71 plugged into the ECU, rather than ground one side of it and cap the other.
Another thing I discovered, was that when I initially used a 1st gen. USDM TT ECU, my car would work, but it would be very ruff (I am assuming that would indicate that the timing was out of whack). The problem was that my car is a 2nd gen. and as such has the new style crank and cam angle sensors. As soon as I switched the ECU for a 2nd, gen. JDM TT one, that problem was fixed (along with the fan operation).
Here are the pages from the manual that shows the description for the function of pin #71:
I have a "BigTyia Ground Wire Kit". It is well made. This rocket scientist knows his stufff. Thanks for adding to this post.
Please read my edit, because things changed since yesterday... It seems like in my case (2nd gen. JDM N/A car with 2nd gen. JDM TT ECU) pin #71 should not be grounded! It would also seem that pin #71 is not the "starter relay signal" as Big Tyla suggests, but the "inhibitor switch" as it is recorded in the manual, the relevant pages of which I posted above. However, under "Complete listing of ECU terminals and assignments for 1991-1993 DOHC engines:" the Stealth316 website has pin #71 listed as "chassis ground" for M/T and "starter relay signal" for A/T. That is in direct conflict with the page of the manual that I posted above. That page came also from Stealth316... Confusing! I, personally, choose to believe the manual than the Excel file, since the Excel file could have been prepared with mistakes... According to the pages from the manual, pin #51 is "ignition switch" with no specification to M/T or A/T, which must mean that it is the same for both. In the Excel file, pin #51 is indicated as "starter relay signal" for M/T and "Park/Neutral Switch" for A/T. That is where the mistake in the Excel file shows again, in my opinion... Nowhere do I see in the manual pages that pin #71 is "chassis ground" for the M/T.
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