want2rally

okay i have a problem with my 91 accord lx i get a check engine light saying my O2 heater circuit is bad (code 41). ive replaced my o2 sensor. same problem. i have a friend that said resistence on aftermarket o2 sensors could cause this so use oem ntk/ngk sensor, but for $200+ or even 100 i cant see me doing that. has anyone had a similar problem, anyone have a good solution? once the o2 sensor is hot, idle for 5 min or driven for a couple, i can turn the off car and restart and check engine light will be off, so i am assuming the o2 sensor is working properly other than heater circuit.

want2rally

I think I am going to try to add resistors in the line to the heater circuit so i can get the factory spec resistance. I'm not sure if this will work though? Any theories? Ideas on what type of resistors i should use? any help is appreciated. Thanx!

JimBlake

Sounds like the original problem wasn't the senor heater itself, but the car's wiring for that circuit. What did you do to check that out?

The heater itself should be 10 to 40 ohms, measured between the two same-color wires (black?). What resistance do you measure? Neither of those heater wires should have any continuity to ground. Check that?

Can't tell you what resistors to use until you check out this other stuff. If any part of the heater circuit shorts to ground, then resistors aren't gonna fix it anyway. If the heater circuit doesn't get power (from main relay) then resistors aren't gonna fix it.

want2rally

when i checked everything seemed to be fine the only thing that was wrong was the resistence on the o2 sensor was slower than an oem one. so Im figuring that is what is tripping the code, so if i can add more resistence it will work as the oem does, no more check engine light. let me know what you think

Chiovnidca

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by want2rally &raquo;</TD></TR><TR><TD CLASS="quote">I think I am going to try to add resistors in the line to the heater circuit so i can get the factory spec resistance. </TD></TR></TABLE>
A 1000 ohm resister works to trick the ecu into thinking there is a good o2 heater. Works good when the o2 heater is open anyway.

want2rally

Chiovnidca, have you tried this? do you have any specific instructions on how to do so?? I really want to get rid of the cel without spending a load on a new o2 sensor when i already have a brand new non oem one i spent $50 for. Thanx

JimBlake

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by want2rally &raquo;</TD></TR><TR><TD CLASS="quote">... the only thing that was wrong was the resistence on the o2 sensor was slower than an oem one...</TD></TR></TABLE>What's it mean for the resistance to be slower? What did you get when you measured it?

Check out the heater circuit in the car: Does the heater terminal get power? Is there continuity back to the ECU? Does either leg of the heater circuit have continuity to ground?

notoriousB

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Chiovnidca &raquo;</TD></TR><TR><TD CLASS="quote">A 1000 ohm resister works to trick the ecu into thinking there is a good o2 heater. Works good when the o2 heater is open anyway.</TD></TR></TABLE>
1000 ohm? I've heard to use two 10w 10ohm resistors in series, won't a 1000 ohm provide too much resistance?

I need to do this myself for my wideband setup so I'd be grateful for any experienced input on the ol' resistor trick.

Chiovnidca

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by notoriousB &raquo;</TD></TR><TR><TD CLASS="quote">1000 ohm? I've heard to use two 10w 10ohm resistors in series, won't a 1000 ohm provide too much resistance?
</TD></TR></TABLE>
The instructions that came with my Hondata setup for my civic suggested the 1000 ohm resister trick when running a wideband. (to keep the heater code from popping up) Ran it like that for a little over a year and then went back to a stock sensor with no problems.


Modified by Chiovnidca at 9:14 PM 9/15/2005

JimBlake

That's good to know. I guess the ECU will tolerate 25 times lower power than it's supposed to be. I always figured you'd have to have the right resistance to match the sensor. (20 ohms would be right in the middle of the 'correct' range)

1000 ohms would give about 0.2 watts, which is a much more 'normal' resistor, too. So heat sinking would be easier.

notoriousB

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Chiovnidca &raquo;</TD></TR><TR><TD CLASS="quote">The instructions that came with my Hondata setup for my civic suggested the 1000 ohm resister trick when running a wideband. (to keep the heater code from popping up) Ran it like that for a little over a year and then went back to a stock sensor with no problems.</TD></TR></TABLE>
do you recall how hot the 1000 ohm resistor got after using it for a while?

I've heard that using 2 10w 10ohm resistors will get VERY hot. I'd much rather a more 'stable' & safe solution and 1000 ohm sounds like it.

JimBlake

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by notoriousB &raquo;</TD></TR><TR><TD CLASS="quote">I've heard that using 2 10w 10ohm resistors will get VERY hot. I'd much rather a more 'stable' & safe solution and 1000 ohm sounds like it.</TD></TR></TABLE>Your 20 ohms would give you a little more than 9 watts total. Get a 7 watt nite lite, plug it in for a while, & touch the bulb. It gets pretty hot, but it's supposed to be designed for that. That's the reason for using 10-watt resistors, so they don't burn themselves up.

I'm sure you could set any light fixture on fire if you wadded up newspaper & stuffed it around the bulb, but you don't see lots of houses burning down even with lots of 75 watt or 100 watt bulbs. Common sense...

Using a 1000 ohm resistor, that's only 0.2 watts, which would be much easier to handle the heat.

notoriousB

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by JimBlake &raquo;</TD></TR><TR><TD CLASS="quote">I'm sure you could set any light fixture on fire if you wadded up newspaper & stuffed it around the bulb, but you don't see lots of houses burning down even with lots of 75 watt or 100 watt bulbs. Common sense...
</TD></TR></TABLE>
well no kidding.

my concern is placing a really hot resistor (or 2) inside my car or engine compartment - sounds like the 1k ohm is the way to go, may try this this weekend if I can find a 1k ohm resistor.

JimBlake

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by notoriousB &raquo;</TD></TR><TR><TD CLASS="quote">well no kidding. </TD></TR></TABLE>Yeah, but really, 10 watts is pretty small compared to the heat given off by the exhaust pipe or even the headlight bulbs. You just have to mount it in the open. But 1000 ohms (0.2 watt) makes it real easy.

Chiovnidca

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by notoriousB &raquo;</TD></TR><TR><TD CLASS="quote">do you recall how hot the 1000 ohm resistor got after using it for a while?

</TD></TR></TABLE>
Never saw any sign of it getting hot. It was just a cheap resister i got at radio shack, 1/4 watt if I remember right.

want2rally

resistence is lower sorry on the aftermarket than oem o2 sensor. i just bought 100k-ohm resitors (1/2 watt 5% tolerance) at radioshack do you think that if i splice one of these onto the heater wire it will do the trick?

want2rally

okay just to let you all know i added a 10ohm 1/4 watt resistor to one of the heater wires on the o2 sensor and sure enough the cel turned off so no need to get an oem honda o2 sensor for $200. SWEET!!