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Something not right somewhere
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Posted by Ari [Email] (#2847) [Profile/Gallery] (more from Ari) on Wed, 23 Feb 2005 11:45:31 Share Post by Email
In Reply to: Re: Hey, I wasn't done!, Jamey, Wed, 23 Feb 2005 10:28:27
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According to my schematics, the injectors have a common connection to 12 volts through the main relay. Now, the schematic I'm working to may be wrong. I've got a much better one, just not handy. The ECU connections are pins 3, 4, 5, and 6 on the ECU.

As to how the IAT sensor could have screwed up the ECU, I don't know. The ECU output is a switch to ground, most likely a darlington transistor. It is designed to deliver a lot of current to an inductive load (injector), which means that it can deliver a lot of current and withstand voltage spikes. At typical injector is on the order of 3 or 4 ohms. The IAT sensor is just a resistor that varies with temperature. Depending on the temperature, it runs between 10K ohms and about 300 ohms (hot) Compared to driving a fuel injector, that's a walk in the park. It shouldn't damage the ECU at all.

Looking over the schematic, I would check your wiring again. Make sure that you indeed have the right injector connector on the injector. One side of the Injector #2 (green/red wire) is connected to ECU pin 4. The other wire (blue/red) should be connected to 12 volts when the engine is running.
The IAT sensor has two identically colored (yellow) wires. One goes to pin 33 of the TCS system, the other goes to pin 68 of the ECU. If you don't have TCS, the black wire on the IAT goes to ground; the yellow goes to pin 68 of the ECU.

I take it that when you measure across the injector connectors, you get 10 volts or 0, which you are calling ground. 0 (ground) volts would be 10 volts (or so) on both sides of the injector, which is a closed injector. When you see 10 volts across the injector, current flows, and the injector squirts. So you're seeing 10 volts all the time across injector #2. That's why I would make sure that it is indeed the #2 connector, not another one. Measure continuity between that and pin 4 of the ECU, just to make sure.

OK, could something have blown up the ECU? Yes. It is an electronic device, and they can and do die. It is unlikely that putting a light load like an IAT instead of an injector would damage the driver in the ECU. But not impossible. But I'd do some more checking. Are the wire colors right on the wires?

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