OBD2>OBD1 Conversion Harness Issues.

[VT3C]

we were trying out KB's Harness adaptor on the weekend.

We Tried: JDM P30, AUS P30, AUS P28 to run the EJ8's D16Y8 and it worked OK and revved over 8000RPM and seemed to make good power right up untill rev-cut however there seemed to be NO VTEC engagement.

Does anybody know why this would be ? surely the convertor harness would re-route the VTEC wires appropriately etc..

what could cause this ?

Interestingly, I tried out the AUS P30 in my car (running a JDM B16A) and while it was a lot smoother and 'lighter' and VTEC at 5,500RPM was nice (vs. 5800RPM) but man it made no power according to my butt-dyno.

will prob do this ECU test on Dyno Day this saturday for any who are interested.. but need to get the Convertor Harness issue sorted out ASAP please.

thanks...
- Bede

[ECU-MAN]

you should connect a test light to your Vtec solenoid, take it for a spin and see in the test light comes on.

vtec might be engaging but because the rom doesnt match the engine, fuel and timming maps might be out,

connect a test light to OBDI A4, make sure you can see it while driving, see if it lights up when Vtec kicks in. or at least tries to light up then goes out.

what is the resistence of the VTEC solenoid

[LVNIT]

Does an EJ8 have a VPS? OBD2 cars dont have a VPS do they?

This is the problem I had, because im using an OBD2-OBD1 conversion harness, the OBD1 ecu is searching for the VPS. Now as your car is OBD2 and does not have the VPS, no vtec :)

This would also explain why the JDM b16 would work, as it has the VPS, AFAIK

I had to connect A4 to D6 I think it was, so vtec would engage. I guess ECU-MAN will clear this up if I have got it wrong, but im confident thats the issue ;)

[VT3C]

dang KB - he HAD a VTEC light and took it out 'cause it's rice' HAHAHA

[ProECU]

On your Conversion Harness, make sure OBD2A(pinA8) OR OBD2B(pinB12) connects to the OBD1(pinA4).

[ECU-MAN]

Does an EJ8 have a VPS? OBD2 cars dont have a VPS do they?

This is the problem I had, because im using an OBD2-OBD1 conversion harness, the OBD1 ecu is searching for the VPS. Now as your car is OBD2 and does not have the VPS, no vtec :)

This would also explain why the JDM b16 would work, as it has the VPS, AFAIK

I had to connect A4 to D6 I think it was, so vtec would engage. I guess ECU-MAN will clear this up if I have got it wrong, but im confident thats the issue ;)

thats what I thought at 1st as well, but KB told me its code 21 not code 22.

still could be it thought. OBDI ecu will look for the VPS unless its disabled, faked or bypassed

[KB]

WHat is this VPS you speak of?

[KB]

and how would one trick the mofo

[ProECU]

Vtec Pressure Sensor.

Any freeware ECU program can disable it for you...

[KB]

Cheers Man.

BTW Can I not ghetto it up some way? Like hook it up to a circut of some sort, applying a certain voltage to it to trick the ECU into thinking that the correct pressure is there?

[VT3C]

ghetto it up

GHETTO is the way of the Future !!

[fried]

if the ecu is tuned to the most ideal situation, ur butt dyno not telling u anythign is EXACTLY what should be happening. vtec engagement butt dyno feeling is very minimal. this is because the most ideal situation would be a linear power curve, so vtec would only be noise.

obvioulsy - "ideal" is a different circumstance in everybody's books.

[LVNIT]

Vtec Pressure Sensor.

Any freeware ECU program can disable it for you...

Neither Uberdata or Crome will disable the Vtec Pressure Sensor, not in their current releases anyway :)

[ProECU]

Yeah i'm aware.
Crome has an issue with Vtec Disengaging when VTP is disabled...Nasty!

But yeah, I'm glad people are starting to listen to these issues.

[VT3C]

On your Conversion Harness, make sure OBD2A(pinA8) OR OBD2B(pinB12) connects to the OBD1(pinA4).

this makes sense to me.. OBD2a vs. OBD2b... is simple to have sent the wrong a/b harness.

[ECU-MAN]

KB

you can ghetto this useing a 12v relay

you wire up the relay to the Vtec solenoid, so when vtec engaged it enrgises the relay mimicing the VPS open circuit.

[Bowzer]

This is a simple fix! On OBD1 cars there is a VTEC Solenoid and VTEC Pressure switch wire.

On OBD2 there is no VTEC Pressure Switch sensor, so OBD1 will be looking for it to work. Simply tap a wire from the VTEC Solenoid and tap that into the VTEC Pressure switch and it will solve your problem.

Otherwise use the method above i.e edit the ROM and manually disable the VPS

[barefootbonzai]

This is a simple fix! On OBD1 cars there is a VTEC Solenoid and VTEC Pressure switch wire.

On OBD2 there is no VTEC Pressure Switch sensor, so OBD1 will be looking for it to work. Simply tap a wire from the VTEC Solenoid and tap that into the VTEC Pressure switch and it will solve your problem.

Otherwise use the method above i.e edit the ROM and manually disable the VPS

So lets say on KB's car, how he had a vtec light, using that same wire connect it to the VPS pinout on your ecu instead of the vtec light will solve the problem? Does the VPS do anything? Cause if this is a work around seems like one useless sensor, guess that's y they left it out on obd2 cars.

[KB]

Thankyou all for replys. Will try out tonight. :)

cheers

[barefootbonzai]

Did it work??? I just plugged an OBD1 ecu with a conversion harness in my OBD2 car and no vtec either. About to spice the wires, but just making sure it's worth the effort.

[KB]

Yeh i got TAK now.

Basically all you do is find(ON THE HARNESS) the VPS wire, and find the Vtec "ACTIVATION" Wire and just run a wire from one to the other. It worked for me :).

Good luck