|
Nothing should be able to damage either function on the ECU. Both are well protected-- the input on 12 for WOT and the output on 22 for the CO test point.
Easiest way to check the idle test point (red/white) would be using a voltmeter. Probe the point with ignition on, motor not running. Not running will be obvious in the next step. The voltage should be a logic high - like around 4.5V, maybe 5. That verifies your connection to the ECU. While reading it, rotate your brand-new throttle plate to wide-open. It should then drop to zero. That verifies your WOT on the throttle switch, not that you need to, but it is good to know there isn't some carbon soot inside the switch, dragging the voltage down.
The CO test point is a 511 ohm resistor to a transistor collector pulled up to +12V through 1.5K ohm. You should be able to follow the O2 sensor transitions with either a meter or an LED on that point. It doesn't source much, mostly sinks through that 511 ohm resistor. Pretty hard to damage that circuit with a short, although there isn't any high voltage protection, say, if someone were to wire up their ignition secondary to the connector-- but now I'm getting silly.
If the transistor was shorted, you could measure 511 ohms to ground from that test point with motor off, key out. If it was open, I doubt the LED would light.
You could probably light the LED, though rather dimly, from the idle test point.
Backprobe (peel back the boot and put the voltmeter probe in the back of the connector while it is connnected) the AMM for voltage on pin 6 - the yellow wire to the mixture pot. As you turn the pot from one end to the other the voltage will vary from 0 to about 2.7V. This is a good way to know where you are in the setting; much better than guessing, counting turns or pulling it off and measuring resistance.
--
Art Benstein near Baltimore
|
