yeah i have a 1999 honda civic ex auto coupe. i put a 1997 acura gsr motor swap into it. i bought the obd11b - obd1 jumper harness made by rywire and im running a virgin p72. the problem im having is i can not make my tach work. it comes on when i first start it and then just drops and don't work. i have done all the following i changed the ignitor in the dist. it did the same thing. so i changed the bottom pick up that has the blue tach wire comming out of it and it was a diff year so it gave me a tdc code but the tach still did the same thing. so i changed the pick up back so i have no check engine lights still and everything works besides the tach. i searched and every one was talking about there alt going bad and that the wires in the dist plug having a short or it not making a good connection. so i checked that and nothing. but i did find when i disconnected the alt that the tach worked better than before but not perfect. so i thought ah the alt is bad changed that but nope same thing so than i was thinking my computer was bad or jumper harness had a loose connection or something so i changed my jumper harness to a diff brand new harness mad by a diff company don't know the name but its my brothers but same thing so than i tried a virgin p28 just to see if the tach would work but still nothing so then i tried the stock auto p2p with no need for a jumper harness and it obviously don't run to well considering i had to do the 3 wire to 2 wire iac conversion and the tach works but i have the 2 obvious check engine codes witch was iac and auto tranny controls cause its a manual gsr so im stuck driving around with no tach what so ever but the car runs and drives great so i just need help like any ideas would help just so i can check cause im just over whelmed with things that are wrong i don't know...

 

You said you bought a OBD2a to OBD1 Jumper Harness ... Your Car's Harness is OBD2b. Get a OBD2b to OBD1 Jumper Harness and see what happens. OBD2a uses Plugs A, C, D while OBD2b uses Plugs A, B, C ... Meaning that if you use a OBD2a to OBD1 Jumper Harness on a OBD2b Vehicle then its not jumping the correct Wires to their corresponding plugs on the OBD1 Side, thus causing it to not function properly ... If it was a typo on your part, then I dunno ...

My other guess would be that the Auto Engine Harness uses 4 Plugs, while the Manual Harness uses 3 Plugs. That other Plug on the Auto Harness is probably the one that controls the Tach, etc. So when its connected to the OBD2b to OBD1 Manual Transmission Jumper Harness it does not read it, since that Jumper Harness has no wires for that other Plug to jump to the OBD1 Side.

My suggestion is to get a 99-00 EX M/T Harness and use that. Then use your OBD2b to OBD1 Jumper Harness and retry the P72 and or the P28.

I'm just trying to throw some ideas your way man, not really sure if anything I said will solve your issue. Good luck!

 

yea sorry that was a typo on my part but i really don't want to have to go out and buy the manual harness but yea thats what i was thinking that fourth plug would have something to do witht that but than why would it work ok when u have the alt un plug is where im lost?

 

-The 4th plug is for the automatic tranny.
- The reason the tach doesn't work is because OBD2B civics get their tach signal from the distributor (except manual HXs) you will need to depin A19 at the OBD2 ECU plugs and reroute it to the distributor, connect it to the blue tach signal on the distributor.

 

yea that makes sense i was looking on the ff-squad website looking at the computer schematics and could not find it mainly cause it says "engine speed pulse" but why would that tach work sort of like when i first start it or any other time? But i will go alligator clip what you said to try and see what happens can't hurt ill get back to if it works.

 

well if any one else has any input that didn't work but maybe i did something wrong pretty sure i didn't its kinda simple.

 

Ok, I checked another wiring diagram. Basically OBD1 and OBD2A gets its tach signal from the igniter in the distributor, from there it goes to a junction connector, and then on to the cluster. for testing purposes you could run a wire straight from the igniter to the cluster. If that doesn't work i'd try another igniter.

 

ok well im gona try changing that tonight cause i have some of those laying around but that was the first thing i did but who knows.

 

Ok so i found out after all this that the blue wire coming from my dist was not my tach wire so i checked the guys work that replaced my ignitor in the dist and noticed that when he changed the plug to fit my car he never added the blue wire i needed, so that means there was just an empty tab on the ignitor. so i took my old dist found the wire jumped that to plug where you can add another aftermarket tach in the engine bay all the way in the top right side, it worked so i took that off than jumped that blue wire all the way into the car to the blue wire that was hanging there on the ecu plugs from a19 and it also worked. So instead of running all new wires and trying to hide it i took the orange extra iac plug from the ecu and and connected it to the blue a19 blue than went under the hood and rerouted that wire in side the oem protective casings and hooked up a connector at the dist and bam it all works perfect and hidden so thanks to 94EG8 i would not have got this done so if any one has an auto and switching the swap to an manual b series watch the dist plug when you switch it cause that was my whole problem