Originally Posted by DMD
Has anyone been kind enough to prepare a wiring diagram or instructions to marry up the inputs to the Zt-2 with an MX5? There does not appear to be much installation info on the Zeitronix website and the instructions with the unit are not helping me much. My skills as an auto electrician make me glad I am an accountant.
I am particularly perplexed by the 'o-5v square wave from tach' for rpm input. The tach appears to be dependant on its own microcomputer in the gauge set. Is there another source for this input? The 1G pin of the diagnosis terminal provides rpm info but appears to be 12v according to Miata.net posts. Do I need to look at ecu pinouts?
There is one wire from the Zt-2 for simulated narrowband O2 output to the stock ecu. There are 4 wires coming from the stock O2 sensor, presumably to the ecu. eeny meeny miney moe!
Which wire from the TPS provides the input?
Any of the above info is predicated on the assumption that the wiring harness in right hand drive Australian delivered cars is the same as USA delivered cars.
Any advice would be greatly appreciated.
I can only give you part information, and it may not be useful on your much younger Miata. Mine is a 1991.
First, your stock O2 sensor 4 wire has two heater power lines, one signal ground, and one signal wire. You could probably go through the process of elimination, but it would be best to find an electrical circuit diagram of your car for this and your other questions.
The simulated narrowband signal from the Zeitronix works well, but if you are going to mount your WBO2 in the narrowband bung, it may be too close to the turbo. Again, I don't know the 2003 positioning, but the WBO2 should be mounted at least 12 inches from the turbo.
You could probably identify which wire at the TPS with a volt meter. It will give you around zero to ground before depressing the pedal and around 5 to ground fully depressed. Do this with the key on, but the motor not running.
On my car, I picked up the RPM from the diagnostic plug. I don't know of any posts about this now being a 12 volt signal in later cars nor why it would be. You would best be served by getting a diagram or finding a knowledgeable person with your year Miata.