I recently purchased a plx devices m300 with narrow band option for my ecu.
95 ls.

according to this site
http://www.plxdevices.com/PLXApp004.htm I need to jump the o2 heater wire to ground with a 20ohm 10 watt resistor.

Here is what I did.
first I jumped the heater wire from the ecu to ground with the resistor. That didnt work. So I went back under the hood and tried jumping the two black wires with the resistor. I have pretty much tried every combination with jumping the two black wires or even the green and black. Could someone please shed some light as to what wire is the actual heater ground and heater wire.

After resetting the ecu the cel 41 comes on 3 seconds after I turn on my car.

Thanks

 

The two black wires are the heaters' +12v and control line.

Using a 20ohm resistor should work fine since Helms specs the O2 heater resistance to be in the range of 15-40ohms.

But tying the 20ohm from the ECU control line to ground is not correct. One side needs to go to +12v and of course, the other side to the ECU pin.

 

Hey thanks for the input.

I did use the resistor on the two black wires, and it was still throwing the code. any other suggestions?

 

If you plug the original O2 sensor back in - do you still get the code?

 

actually yes, even after I reset it and plug the stock o2 back in, the cel comes on after a few seconds. So you think its something in the wiring now? but it didnt use to do this before the wideband.
thanks

 

any suggestions?

 

what are you trying to do? datalogging? hooking wideband o2 with the af monitor? need more info on what you want to do.

 

I tried to use a resistor to simulate the heater before as well. It got so hot so quickly that I feared it would catch fire. Now the 02 is just ziptied in my engine bay with the heater hooked up.

 

I am just hooking it up so that it will simulate a narrow band sensor to my ecu so it stops throwing cel 41 and putting my car into constant open loop. no datalogging or anything yet.

 

Ok, so you just kept your stock o2 hooked up and zip tied it? and for the o2 sensor input on the ecu, you just used the narrow band out from the wideband?

 

Yep, I'm running the narrowband simulation out of my wideband controller, with the heater wires for the 02 sensor still hooked up, and the 02 ziptied up in my engine bay.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by swtch7 &raquo;</TD></TR><TR><TD CLASS="quote">actually yes, even after I reset it and plug the stock o2 back in, the cel comes on after a few seconds. So you think its something in the wiring now? but it didnt use to do this before the wideband.
thanks</TD></TR></TABLE>

More than likely, especially if putting the stock O2 back in STILL generates a CEL even though it didn't before.

 

hmmmm. I think i found my answer, thanks man

 

not try to jack the thread, but what kind the wb are you using ricey? i'm getting the dyi 2a0 techedge wideband with af monitor.

 

I may have jacked something up, ill look into it today. but the o2 signal input pin is D14 right? just making sure. thanks

 

Okay, here is whats happening now. Even when I plug the stock o2 back up and reset the ecu, the cel 41 comes on right away. I checked the o2 heater wire comming out of the ecu and it was getting around 15 volts. Does anyone know where the o2 heater ground is located? I might just have to run new wires.

It has to be something with the wiring because if I swap ecu's, still the same code.
Thanks!

 

The ECU IS the ground control for the O2 heater circuit. One side of the heater has a constant +12v applied to it while the ECU has a 'switch' inside of it that it pulses on and off - this is what controls the heater element.

Since you have a meter, there is only so much to verify here:

The actual O2 heater resistance should be 15-40ohms.

There are only two wires - make sure they have continuity back to the ECU and that they are not shorted in any way.

If the sensor and its wiring check out - try another ECU.

 

hey chris, ill check on that. I did try swapping out ecu's and still the same thing, so it has to be something with the wiring.

I was looking around and I read a post that mentioned that the o2 signal input has to be grounded as well. I dont know if this is correct or not.

How I ran the narrow band out of the wideband controller was cut the white wire 5 inches from the ecu and hooked it straight up. So the white wire going back to the engine bay isnt hooked up. Is that wire grounded somewhere? do you think I should just splice the gray wire with the white or feed it straight to the ecu?

Maybe a grounding problem?

 

Well good - at least its not the ECU then.

Yes, the O2 sensor has a signal and its ground (white and green wires).

Where do you have the wideband controller ground hooked up to?

If the white wire leading back into the engine bay became shorted, it wouldn't matter - its not even tied to the ECU, as you've mentioned.

What is this gray wire you speak of?

 

the gray wire is the narrow band signal comming out of the wideband controller, its used to feed the signal to the ecu.

So I guess the gray wire feeding the white isnt grounded, maybe this is the cause of the issue? although its a cel41 o2 heater.

I grounded the wideband to the ecu ground.

 

Can you try getting things back to a stock configuration?

I can't see how the lack of an O2 signal would cause the heater code to be set off.

I mean, if you put the stock O2 back in and make sure that all the wiring is right, and you know your ECU is good - at this point you should get no code.

Get back to a baseline where you know things were working CEL free and then proceed from there.

If after all this, you still get a CEL, then I'd start to question your electrical skills and how 'correct' the wiring actually is.

Before this whole endeavor, you didn't have a CEL, correct? It was only after you started to mess with the wiring?

 

first of all thank you for all your help, I really do appreciate it.

ok

before I swapped for the wide band I was getting cel 43, which wasn’t a big deal because I would be getting the new one.

The only wire that I cut into was the white o2 signal input at the ecu. I also cut the heater wire at the ecu in the begining, but then spliced it back together. The wide band is straight forward

power
ground
narrow band feed (gray wire)
wide band (not being used, for data logging and stuff)

This is why its driving me insane, it doesn’t make sense. I have double and tripled check the wiring, made sure nothing is loose.

I have 20ohm 10 watt resistor connecting the two black wires at the end of the harness. regardless if I plug the o2 back up still the same thing.

Maybe I should just have the resistor on the inside of the car, going from the heater + to the heater - ?

 

A resistor is a resistor - it shouldn't matter where you placed it even if it was at the actual O2 plug in the engine bay. This is where the actual 'resistance' for the heater resides anyway, so placing the resistor closer to the ECU shouldn't help at all.

Are you soldering the wires back together - or using crimps?

I dunno bro - I'd try and get things back the way they were even if this gets you a Code 43. At least you'll know the wiring has been 'fixed' if you can get back to that baseline.

 

hmmmm yea I dont know either, but yes i was soldering the resistor.


lets see. If I was check the voltage out of pin a6 the heater wire, where on the ecu does it loop back to? do you know what pin it is?

I think a25? maybe ill just make a little jumper with the resistor to eleminate the wiring into the engine bay.


Modified by swtch7 at 6:31 AM 11/18/2004

 

Hey, just thought of something, is there a FUSE FOR THIS? I didnt see one but maybe??