Ok, so what are the two switches on a T5 for?

blykins · Feb 9, 2009

I'm finishing up a C4 swap and I'm very confused.

There is a 4 prong connector towards the front of the transmission and a 2 prong connector towards the middle of the trans.

In the wiring schematic, it says the 4 prong switch is for neutral safety and backup lights.

When I wired my reverse light switch up to it, the reverse lights didn't come on. It only had 4.6V to it.

When I wired my reverse light switch up to the black & purple/orange wires on the 4 prong switch, the reverse lights work. (As per the schematic.)

I'm having ECC problems now and I think it's because everyone says that 2 prong switch is a reverse switch, so I put 12V to it to see if the reverse lights would come on.

What is the 2 prong switch for?

tmoss · Feb 9, 2009

the one on the side is for your backup lights and the one one the top is to sense when the trans is in nuetral so you can pull codes from the EEC

blykins · Feb 9, 2009

Ok,

So essentially when I removed the T5, there were two connectors hanging down in the trans tunnel: the 4 prong connector and the 2 prong connector.

I understood it that the 2 prong connector would just wire up inline with my reverse switch on my Hurst Quarterstick.

I did that and the reverse lights didn't work. I checked power from that connector and one leg had 4.6V on it.

I looked up the schematic and it looks like the reverse lights is controlled by the black/pink and purple/orange wires, which happen to be in the 4 PRONG CONNECTOR.

I wired up the reverse switch inline with those wires and the reverse lights work.

This is kicking my butt right now as nothing makes a lick of sense.

blykins · Feb 9, 2009

So Mr. Moss,

What would happen if I introduced 12V from the battery into the wires that go to the front/top neutral safety switch? If that's the switch to tell the ECC that it's out of gear and it's ok to go into KOER, then I could have possibly fried the ECC with that, right?

I'm actually hoping that's what I did, as that would explain why the engine is running like crap and I can't pull any codes at all from the ECC.

I changed nothing else whatsoever on the car, just swapped trannies.

tmoss · Feb 9, 2009

That IS more than likely what you did - you fried the signal return trace on the board for the sensors. If you have (or know soneone who does) some soldering skills, you can repair the trace by bridging the burnt section with a small wire.

There is a hardware difference between an auto processor & a manual processor. The difference is because of the way the NDS [neutral drive switch, manual transmission] & the NSS [neutral safety switch, auto transmission] are wired. They are both wired to the same pin#30 but the auto trans wiring grounds the pin to the starter solenoid & the manual grounds to signal return, during crank mode there is a voltage spike sent to pin-30 so the auto trans processor has a diode on pin 30 where as the manual processor doesn't, most of the time this won't cause a problem unless you get into a prolonged crank condition.

Those that want to convert their automatics to manuals, and swap the ECM, need to clip the wire going to pin 30 or else the ECM will fry the trace off the board. This leaves the manual EEC unable to dump codes, which looks for the loop through the neutral sensing switch of the T5 transmission.

Make sure you have a 5 speed O2 sensor harness when using an A9L or you will fry the trace also. The damage is common when people mismatch harnesses and use an automatic O2 sensor harness with an A9L computer.

blykins · Feb 9, 2009

That's the only thing I can think of that I did. Otherwise the car is exactly the same as it was, including the O2 sensors.

I ordered a new computer. I took the cover off of this one and didn't see any burnt spots, although I didn't look on the underside.

Ok, so what are the two switches on a T5 for?

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