My ECU got fried. One of the resistors that used to be blue is now brown and blue. All the others of the same shape and color have the same resistance if I measure it with a meter, but the burnt one has more resistance (I'm surprised that it still has continuity).

Here is my question. On the pins where the wire harness plugs into the ECU, I can measure the ohms between the pin and the nearest resistor in line with the pin by following the printed circuit. This is what happens. If I measure the ohms between the pin and the lead on the beginning of the resistor, I get a reading, and if I measure between the pin and the lead on the other side of the resistor, I get a higher ohm reading because I have now placed the resistor between the probe on the pin and the probe on the resistor. I want to know if this is normal. It happens everywhere except where the burnt resistor is. On that one, I get the same reading on each side of the resistor. The burned resistor is the bottom most blue one,furthest to the right.



Thanks for you guys info. Oh, and I already have a ECU being sent to me to replace this one.

 

In this pic, I circled the bad one, just to make it clearer.

 

So you're saying the resistor has shorted itself when it burned.? Thats a bit unusual, they normally open up when they get really fried. What resistance value is it supposed to have (ie, what colors of bands does it have)

 

no color bands, it was solid blue like the one to the left of it. I looked at some other ones that are the same size but I can't make out an ohm value.

Also, I have another question, this one is about transistors. Shouldn't there be continuity between 2 of the 3 leads? If I put my probe on one lead, and put the other probe on the other 2 (one at a time) I should get continuity between one, but not the other, corrrect?

 

Sounds like a good way to fry a transistor.

Any electronic repair shop should be able to replace the resistor. Transistors really need to be tested with a curve tracer.

 

I got a new ECU(not brand new, but you know what I mean). I don't want to open it up and go probing around with my meter just in case I mess something up. So there is no way to be sure if there should be continuity through all 3 leads on a transistor? I'm wondering because there are 4 transistors that I checked, and 2 of them have continuity between 2 pins only, while the others have continuity between any 2 of the 3. I have no idea what a curve tracer is. I never got that deep into electronics. I made an A.M. radio once, and that is about as complicated a task I have performed.

Well, hopefully the only thing fried was the ECU.

 

There shouldn't be "continuity" per se between any of the leads, but if its a typical BJT (ie NPN or PNP) and you have a diode tester, you can check to see if the bias voltages are good (a transistor is contrusted kindof like two diodes placed back to back). Just put the diode tester beteen two of the leads. Switch probes, if you don't have continuity (diodes will only conduct in one direction). you should have a aroun .6-.8V drop from two of the leads to the third (from the collector and emittor to the base for PNP, or from the base to the collector and emittor for NPN). and no drop from the emittor to the collector.

This is a bit confusing, I know.

Just from the sounds of it, the two that only had continuity between 2 pins only might be bad, but without a transitor checker (or the process above) you won't be able to really tell.

 

well, I don't have the equipment to check the transistors and it was easier to change the ECU. Thanks for all the input guys.

 

Are you sure that the blue thing wasn't a capacitor or a coil of some kind !? Without stripes it sound suspicious as beeing a resistor.. Since all resistors should have the Resistance in Ohms marked on them via color bands...
Is there any writing on it !?

-DC

 

I'm 110% sure its a resistor. I know the difference between all the parts. The blue ones do have writing on them but the burnt one is too toasted to read. Not all resistors use color codes, like those little flat tan ones for example. I got a new ECU though, but thanks for trying to help.