silver_evo

Hey guys, Im in the process of installing resistors in my wiring to simulate the front o2 sensor heater. (Stock sensor is gone, LC-1 is installed). So i always get P0135 Front O2 Sensor Heater Circuit Failure. Which i expected. The service manual specifies a resistance of 4.5 to 8.0 ohms for the front sensor heater. I got 4 50ohm 10w resistors, I saw the thread and followed its directions, not realizing it was for a rear sensor. https://www.evolutionm.net/forums/sh...d.php?t=268138 So my two options now. Use the 4 resistors in parallel for 12.5 ohms. Or go buy a 8ohm 20w resistor. Now the problem.

I = V / R
P = I * V

I = 14.4 v / 8 ohm = 1.8 Amps
P = 1.8A * 14.4v = 25.92 Watts
So thats too much power for the 8 ohm resistor, its only a 20w resistor.

Now for the 4x 50ohms...

I = 14.4v / 12.5 ohm = 1.152A
P = 1.152A * 14.4 v = 16.588 Watts

The resistors are in parallel, so power gets divided between them, so each resistor is running at 4.15 Watts, they are 10 watt resistors. Which works. My problem is will the ecu be ok with a 12.5 ohm 'heater' instead of the 4.5-8.0 ohm factory spec?

Thanks for any help, i know this is a crazy problem.

Jumperalex

Well as I'm sure you know flowing less current means you aren't going to hurt the ECU by doing it. As for the ECU thinking the heater is bad I suppose you'll only know from testing. Worst case it thinks it is seeing an open circuit, like it is now, and calls it bad. But I can't imagine the criteria is THAT tight.

Or you could find the right combination to just do it right. Instead of 4 x 50ohm 10watt pushing 4.15w you could run 3 x 20ohm 12watt (6.67ohm) pushing 10.37w per resistor. That is cutting it a little close. So you could also look at 4 x 30ohm 12w (7.5ohm) pushing 6.912w per resistor. Both of these resistors are available at Digikey

Or .. you can just order this and really do it completely right:

http://search.digikey.com/scripts/Dk...me=KAL50-6F-ND

Jumperalex

You could even buy a bunch in bulk to cut a bit off the price and sell them to folks on the board or just set it up as a group buy.

silver_evo

Yep, im going to try the 4x 50 and see if the Ecu takes it. If not that KAL50-6F-ND looks perfect. Ive already got the 50ohm ones, so lets see I like that KAL50 also, the heat-sink case looks good. Ill post back and let you know if it works.

Jumperalex

yeah that is why I liked it too. also cleaner than messing about with putting 4 resistors in parallel even using a perf board. Interestingly there are also versions rated for 17volts. One of them, iirc, was only available in bulk, and the other was like $1 more than the one I posted. The picture seemed to be the same but I have to winder if the lower voltage rated one might be smaller? just seemed off that it was a lower voltage but more money. There is never a reason not to use a higher rating part other than the extra cost. [shrug] but maybe this is just a weird reversal of commodity pricing with true supply and demand taking effect [shrug]

Oh and yeah I head ya on the "I alreayd have it front," I hate waiting hehe

dan l

iTrader: (3)

You don't need 4.5-8 ohms. You can use much more resistance (and thus suck less power) by using higher values. I remember someone using a 100 ohm guy and it worked fine.

silver_evo

Works, 100%. After a short drive and multiple ecu on/off's it hasnt come back. Yay for resistors.

dolphin888

A little bit OT, a little bit not OT:
I got CEL P0135. It's Oxygen Heater Circuit Malfunction (Bank 1, Sensor 1).

Q: Is it front or rear heater?????

Tuner@Swift

iTrader: (1)

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