No, everything is thankfully external. I traced the single wire that runs to the ECU a few days ago... Inside the case, it runs to the no.1 injector pin via a 10k resistor. That's it.
The device actually has a whole bunch of functions: Clock (the unit takes the place of the clock in the legend), distance to empty indicator, trip odo, current fuel economy, average fuel economy, engine oil level, coolant level, washer fluid level, service and oil/filter inverval odos. It isn't installed yet, so there may be other functions lurking in the software that I haven't come across with simple power and ground.
Lets see... The wire from the lighting switch is 12v+ to dim the display, the pink wire from the ECU is the switched ground injector signal via 10k resistor I was talking about above.
The fuel level sending unit needs to output 2-5 ohms when full, 25.5-39.5 ohms at half tank and 105-110 at empty. Conveniently the same values as the CRX sender. I haven't looked at the low fuel sensor... Judging from the circuit diagram, it's the same design as found in other Hondas and Acuras. I can look up specs if you want.
The coolant temp sender needs to output 158 ohms at 54?C/129?F and 32-49 ohms at 85?-110?C/185?-212?F. Also stock CRX values.
The fuel filler door switch is part of the door release lever, so I assume it's triggered momentarily when you pull the release... I haven't investigated further.
The engine oil level switch is in the oil pan... Too much work as far as I'm concerned. The only odd thing I noticed is that the corresponding wire in my donor car showed about 50 ohms of resistance. Not no connection or good continuity, but 50 ohms. The dipstick showed way over full, so I assume water got in the crank case... The switch may have been damaged.
The coolant level switch is built into the lid of the radiator overflow bottle... Simple on/off operation via a reed switch and float with internal magnet. The washer fluid switch is installed in the bottom of the bottle, similar design to the coolant switch.
The speedo and pulser are cable driven, so I assume that's also typical Honda spec... Four 12v pulses per cable revolution or whatever it is.
If you're going junkyarding, the display is on the top of the dash above the radio, HVAC controls and such. Make sure you've got an info display equipped car before you start disassembling things... The standard issue clock looks very similar to the info display when unpowered.
The control unit is above the glove box. Once disconnected from the box, the wiring harness between the display and control box can be pulled back towards the display intact. That way you don't have to deal with resoldering the wad of wires between the two.
So do you have a diagram for a good 2/3 pulsewidth scaler? It strikes me as a problem that might necessitate a processor, but I don't really know. Simply dropping every 3rd pulse might work as well, but it's hard to say how the info center would react to that.
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