1JZ ECU - help me ID this resistor (I think it's a resistor!)

[Hydra]

Hey,

I'm trying to work out what the gray component is in the middle of this pic:


Click the image for a stupidly large version.

I put a multimeter across it (it seems to, on one side, just head to a pin that goes to the loom). A hopefully good ECU (the one running my car) shows maybe 1 ohm of resistance. An apparently busted ECU was showing about 25kohm. Said ECU also has said component surrounded by burn marks and I can't make out the writing - it was burnt off! If we take a look at a more... macro pic we can extrapolate that it's a "430K" item.


Click the image for a stupidly large version.

I'm really unsure if this is a measure of resistance considering the bugger all resistance I see testing a working ECU.

The pin it heads to is "HT". Interestingly enough this goes to the oxygen sensor - just so happens I have poor fuel economy (and popping from overfueling).

Can anyone confirm what resistance I should be seeing on this component? Or even what it is? I'd like to know if replacing it would be worth while.

[amichie]

Those things are low value resistors. The HT is the heater circuit for the o2 sensor.

It is in series with the heater so that if the heater goes short ciruit the ECU doesn't blow up.

7M ECUs use them in series with the injectors also.

O2 Heaters are about 20 watts when cold and about 5 Watts when hot.

Check your good one again that said one OHM then short your multimeter leads together and see what that says. The difference should be approx the resitor value you need.

Good luck

[Hydra]

Wont shorting the leads just show 0 ohms? I don't follow on how that will give me the resistor value I need. I'll throw a multimeter over it again tonight.

Does it act like a fuse, increasing the resistance when there is a short circuit (and frying itself too...)

[amichie]

Wont shorting the leads just show 0 ohms? I don't follow on how that will give me the resistor value I need. I'll throw a multimeter over it again tonight.

Does it act like a fuse, increasing the resistance when there is a short circuit (and frying itself too...)

It just gives you the lead resistance which is small but not zero.

[Hydra]

Cool - thought as much.

I'm guessing it's going to be about 1 ohm That means the resistor in my good ECU isn't really resisting, more sitting there allowing current through.

[amichie]

That's it.

[Hydra]

So I'm thinking, I could just put a fuse across it if it's basically 0 ohms. It should draw only 1-2amp max if i've got my calculations correct. That way if it does short the fuse should save the ECU.

Still, I'd like to confirm the resistance against another 1jz ecu in case it's faulty.

[wilbo666]

I had a look at one of my spare 1JZ ecus.

Says 0.43Ohms, there is a K after it, but it def isn't kOhms

Measures ~0.5Ohms with multimeter also

Looks 3+ Watts

Resistor = easier than fuse.

Cheers
Wilbo

[Hydra]

Cheers for that - Looks like I'll leave it be in the good ECU

[DrNick]

Did you isolate it from the rest of the circuit when testing it? If not then the 25K on the busted one was probably the current flowing through the circuit through other paths - the actual burned component may be completely destroyed and allowing nothing to pass through.

[neal]

DrNick is right you should de-soldier and then check, then replace if faulty or soldier back on if its ok.

[Hydra]

It's isolated when it's not plugged into the harness. One side of it goes to the HT pin only, the other side to what appears to be a voltage regulator.

[wilbo666]

One side of it goes to the HT pin only, the other side to what appears to be a voltage regulator.

Transistor actually

Not everything in a TO-220 like package is a voltage regulator

2SC4552

Cheers
Wilbo

[Hydra]

Shows how much attention I paid to it huh Cheers