Driving a 97 Civic HX with 5-spd and OE 5-wire wide band O2 sensor.

I want to tap into the voltage output from the 5-wire O2 sensor.
Which wires to use?

First O2 sensor wires are:
yellow
orange
red
white
black

Presumably two will give the voltage readout indicating amount of rich/lean?
Getting that voltage to read on a simple display will tell me when I'm in lean burn and when not. (For this car it's all about mpg not power)

I already know that the range will be from about -0.8V to about +0.8V; lower numbers are leaner.

Thanks

 

The documentation I have shows the Civic HX with a D16Y5, 5sp using a PHO2S (LAF lean air fuel) sensor with 7 wires. Not sure about the 5 wire.

It doesn't matter if it's a 5 or 7 wire. The wire that you would want to tap into would be the wide band signal wire. It should be a WHT wire connected to the ECU @ pin D7 (LABEL signal). The voltage range read at D7 with car running can be from 0.3v - 4.9v from the wide band 02.

Where did you get your voltage readings from?

 

the "7-wire" wideband used by the HX is actually a 5-wire, two wires are actually a cal resistor in the connector. (same with the VX, look up the NGK L2H2 or L1H1 for specs)

you can't use a secondary gauge on an ECU controlled wideband, there are actually two signal wires and a reference. It's far from the 0-1V signal on the standard 4-wire O2.

I've never heard of anyone doing it, but it is possible to place a second wideband in the stream close to the OEM sensor, then pull the readings off all three wires and do some mapping. It's going to be a little odd, but I'm sure it can be done.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Relic1 &raquo;</TD></TR><TR><TD CLASS="quote">the "7-wire" wideband used by the HX is actually a 5-wire, two wires are actually a cal resistor in the connector. (same with the VX, look up the NGK L2H2 or L1H1 for specs)</TD></TR></TABLE>

OK it's just that the wire diagrams that I have in my 96-00 Civic Honda Shop manual are showing 7. I didn't really check the diagram to see if they all came out of the sensor or not. When I looked at the troubleshooting and testing for the Hx wide band it showed an 8 pin connector with 7 marked pin locations so I just assumed that all 7 wires left the sensor. I have never worked on a LAF HX before.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Relic1 &raquo;</TD></TR><TR><TD CLASS="quote">you can't use a secondary gauge on an ECU controlled wideband, there are actually two signal wires and a reference. It's far from the 0-1V signal on the standard 4-wire O2.

I've never heard of anyone doing it, but it is possible to place a second wideband in the stream close to the OEM sensor, then pull the readings off all three wires and do some mapping. It's going to be a little odd, but I'm sure it can be done.</TD></TR></TABLE>[/quote]

Saying that it is far from a 0-1V signal (aka narrow band) 4 wire sensor is very true, because the LAF PHO2 Sensor is a wide band 0.3V to 4.9V sensor. If all the OP wants to do is watch voltages go up and down while he's driving then the wht wire (D7) is the one he's looking for. I never got that he was running any tuning software in his original post.

What tuning software are you going to be running to track this brucepick?

I'll have to check but I could have sworn that the NGK WB voltages were already in eCtune's wide band drop down menu. Someone out there must have a voltage reference map for these OEM WB sensors by now?

 

actually the wideband itself doesn't put out 0.3-4.9V, it's closer to what the OP stated of -0.8 to +0.8, but on both wires, then the reference comes into play as well. Reading it directly would require a little software to monitor all three lines.
If you have an external driver for the wideband (DIYWB come to mind) then you'll end up with the output you describe. And will be able to feed it into an ECU... but that's not possible when the ECU is controlling the wideband.

 

Thanks guys.

You've convinced me - tapping into the O2 leads is not the way to get where I want to go. Two output wires, a reference, software to decode it - ya gotta have a deep background in this and really be dedicated to retro-engineer that system.

Any tips on how to have an indicator for in/out of lean burn??

It's about mpg. The HX has no gauge telling you when you're in/out of lean burn. MPG supposedly goes up about 30% in lean burn and I suspect that's true. So for an mpg fiend like me it's worth some effort to get an indicator working, if possible.

I'm just running the oe engine control system and expect to stay with it.


Modified by brucepick at 5:41 PM 10/20/2008

 

honestly the HX ECU doesn't use the lean burn mode near as much as the VX does. If it weren't for the slightly more fuel required and emissions I'd recommend dropping to the OBD1 VX ECU for better mpg figures.
the only real way to know if it's in lean burn mode is to buy an aftermarket wideband and monitor the A/Fs in the exhaust, lean burn will be in the 16 range.

Something I've always wanted to try, to monitor a HX with a custom OBD2 communication logger, just to see if anything changes when going in and out of lean burn. There has to be something if even a slight variance in the injector pulse duration.

 

RESURRECTION!!!

Bring this thread back to life!! I want to know what happened! I have a 98 hx myself, and after doing some reading, I find that the scan gauge II, probably the most popular hyper miler instrument, does not read lean burn mode mpg correctly, since it calculates mpg based on air intake info and assumes a constant air fuel ratio. which sucks for the lean burn boys.

Theoretically speaking, somewhere inside the ecu there has to be some kind of circuit or something that says to engage or disengage lean burn mode.... right? Shouldn't it be as simple as to rig up an LED light on that circuit?

Thanks for all the good info here guys.
John

 

just to bring this back from the dead (again), I am considering doing something similar, but just an LED indicator that will come on at a specific voltage. my car has the OBD-1 VX swap in it, and I read a while back of people using a multimeter across two ecu pins to determine their AFR based on a chart or something. my idea was to have something like that but use a micro-controller to turn on an LED when the AFR was above a certain point, and a second one when below that point. I have yet to look into it past this point, but if anyone is thinking about this idea still, I think its a feasible and beneficial one to try to help you save gas, heh.

 

Bring this thread back to life!! I want to know what happened! I have a 98 hx myself, and after doing some reading, I find that the scan gauge II, probably the most popular hyper miler instrument, does not read lean burn mode mpg correctly, since it calculates mpg based on air intake info and assumes a constant air fuel ratio. which sucks for the lean burn boys.

Theoretically speaking, somewhere inside the ecu there has to be some kind of circuit or something that says to engage or disengage lean burn mode.... right? Shouldn't it be as simple as to rig up an LED light on that circuit?

John, Yes I am another HX (2000) owner who wants to find a simple way to detect when the ECU signals for LB operation. After Christmas I hope to purchase an AF ratio gage LINK that will show the change in AF ratio as the car goes into LB mode. If you have found some other way that is simpler and less expensive - please send me a note about it. Thanks, Rob

 

I have a PLX wideband m250 make to use L1h1 sensor like you have.`
I could sell it

 

Are you speaking of this one ?
LINK

 

M-300 use Bosch sensor

M-250 use NTK sensor

 

Relic, I am in the midst of putting a second wide band O-2 in my exhaust manifold just above the CAT. If I fail to get back to you holler at me and I will let you know how it works. It will be feeding an AFR gauge for the purpose of reading Lean Burn.

 

Relic, I did not get back to you. I installed the O-2 sensor at the upstream side of the Cat. Since the Cat is also the exhaust manifold it is too close to the engine. It was meant to be about two feet downstream of the engine which is impossible. The reading came in but they were so fast and alternate I thought I may ruin the O-2 sensor so I took it out. The sensor would read up to 19:1 maximum -- it would go right up to that when entering Lean Burn. If the scale went higher I may have read a higher AFR but that served the purpose I wanted and that was to see that the Scan Gauge was reading that signal that Brucepick posted on the Ecomodder forum.