ZZ28ZZ

I'm currently checking my freshly assembled DIY-WB-O2.
I'm using the following as a guide.
http://www.diy-wb.com/diywbchk.htm

Everything looks good till I get to step #34.
When I close the "switch", the voltage drops abt .01 volt and stays there. I've replaced C10. Isolated and verified R18 and R34. Hoping U2 is OK.

Same issue with step #36. Voltage initially drops to -2.7, but never starts increasing.

On step #42 (using a 100 ohm resistor) J8 starts at 2.5Volts. Drops to 1.4 when switch is closed and stays there. It never starts to increase..

At what point am I supposed to connect the O2 sensor to the circuit?? I was wondering if that was why the voltages aren't changing in the preceeding tests.

RBob

iTrader: (1)

Don't worry about those tests not operating as listed in the check out. They depend upon the op amps having an input offset mismatch. The better the op amps the more likely the test won't work.

Before connecting the sensor, hook a voltmeter to the heater output of the DIY-WB. Power up the circuit while watching the meter. The voltage should start at arounf 6-7 volts and climb to ~ 10.4 V in 10 seconds or so. At this point the heater ready LED should come on. If it doesn't it may be in backwards.

If it does and the voltage is at ~10.4 volts, then disconnect all the test gear, hook up the sensor, and power it up with at least a 14 V, 2A supply.

Time how long it takes to heat up. You'll need to add the 15 ohm resistors across the 1 ohm (the 5W'r) until the heat up is ~30 seconds. (start with at least one).

It should free air at ~ 4.0V (3.9 - 4.1 v).

Be careful as the senser will get hot (800 C internally).

Once in the car, always power up the circuit whenever the engine is running.

RBob.

ZZ28ZZ

I added one 15 watt resistor across R4. LED comes on in 45 secs
with the sensor connected. Heater voltage is steady at 10.34v.
That's the good news.

Bad news is when the LED comes on, the Vout voltage drops from 2.505v DOWN to .078v in abt 30 secs then stays there.
It's supposed to CLIMB to ~ 4v. This is with sensor laying on the test bench.
I've double checked the sensor wiring. It's OK.

Anyone know a where a good troubleshooting guide is other than the one I referenced previously?

Anyone know what the O2 sensor voltages are supposed to be?
Mine are:
red= 3.87v
white= 3.45v
black= 3.83v

Power supply is a 20amp Astron.
Supply voltage measured on the board is 13.5 volts.

RBob

iTrader: (1)

Place another 15 ohm resistor in place. Warmup should be 30 - 35 seconds.

Did you wire the CalR resistor into place? It is the two pins on the sensor that do not have any wires on them. They go to CalR (J9 & J10?) on the PCB. No polarity.

To measure the sensor voltages ground the meter to the black wire, then measure the red and white. With an operational system red will be ~450mV. White can vary from +2 V through -2 V.

RBob.

ZZ28ZZ

Added another 15 ohm and heater warm-up is now 31 secs.

Didn't know abt connecting the 2 extra pins on the sensor plug. Connected them to J10 and J9.
Vout is now starts at 2.505 and drops to .966v.
With meter grounded to sensor black wire; I get -.389 on the white wire and .033 on the red wire.

RBob

iTrader: (1)

OK, the warm up time is good. With the red sitting at 0.033 V and the white at -.389 then the pump circuit isn't working correctly. It is like it doesn't have enough omph (thats technical for drive current). Double check for solder shorts, the direction of the op-amps (by the notch), and the 74HC4066. Then check that the diodes D6 & D7 are in correctly along with the transistors Q3 & Q4.

Some of the pads in that area are close together, so again check for solder shorts. I'll do some checking of what some of the voltages should be with a sensor in free air.

RBob.

ZZ28ZZ

I replaced U2 cause I thought pin 14 should have had 4 volts since pins 12 and 13 were more than .1 volts apart. (damn thing still reads 2.7 volts!)

Rechecked Q3 and Q4 and their respective diodes for correct installation.
Ran through all the voltage checks again and everything was exactly like last time except on step 33, I measured 2.674v and now it's 2.735v.

Connected the sensor and WALA!! 3.95 volts on Vout!!!!!

I can't believe it,, I think its actually working!

When I bought my sensor connecting cable, I was figuring on 5 wires (didn't know abt the CalR wires) and settled with 6 conductor trailer light wiring. Oh well,, back to the 24 hr auto parts store again.

Can the sensor be bench tested? I've heard of blowing propane on the sensor to make it read rich, but that was on a regular ol O2 sensor.

Thx for the help RBob!!

I'll let you know how it works out once it is all hooked-up in the car.

RBob

iTrader: (1)

Your welcome and congrats! If you'd like to see it go rich on the bench use an UN-lit lighter and wave it over top of the sensor. Just enough to get some of the gas to go into the openings. Don't go overboard, once at 1.5 V or so that is enough.

The sensor gets rather hot so be careful handling it after it has been powered up.

RBob.

ZZ28ZZ

Went for my first WB-02 test drive tonight.
Was reading 2.5-2.6v while cruising at 60-65 MPH. Laptop was showing 129BLM and 128INT. That seems pretty close.

During moderate accel (30% TPS), voltage was 2.3-2.4v. Thought maybe it shold be a little lower..

At WOT I was reading 1.8-1.9v. Seems a little rich, but safe.

I was a bit confused when to start the sensor heater.
I switched the heater on and was waiting till the LED came on before starting the eng. Waited abt 60 secs. Started eng anyway and LED came on in a few seconds.

Apparently the system voltage (eng off) is too low to get the 02 heater up to temp within the 30-35 sec window.

Should I "pre-heat" the sensor, start eng and let it come on up, or,, should I start eng and then turn-on the heater?

Notice the LED gets brighter and dimmer as I'm cruising.
Is that normal?? Heater oscillating to keep temp right???
At idle, it's bright and steady. Shaking controller has no effect on LED intensity.
It never went off.

Just today, found out the sensor is supposed to be mounted at a 10 deg or greater angle for condensation removal. Looks like another trip back to the muffler shop.

RBob

iTrader: (1)

I usually give it 10 seconds or so of warm up then start the engine. The one thing to remember is to always have the unit/sensor powered up whenever the engine is running. And the reverse is true, don't leave the unit/sensor powered up unless the engine is running.

Yes, the tip end of the sensor should be at the lower end of a slight downward angle. These sensors run at ~ 800 C and will crack (internally) if hit with condensation.

As for the dimming LED there is a fix for that. You will need a small capacitor of .01 uf or there abouts (.1, .01, .001, .047 uf). Basically any value between .1 uf and .001 uf, a small disc or mono with a voltage rating of 12 to 50 volts will do.

On the DIY-WB PCB, part D5 (small three legged black plastic device), solder the cap across pins 1 & 3 (the two outer). I find it easy to lay the cap flat on the PCB and solder it onto the pads.

What happens is that the circuit can go into oscillation. The capacitor prevents this. Does it look like the LED may actually be flickering when it dims? If so that's it, and this is the fix.

WB's are cool. . .

RBob.

gregger2k

RBob, thanks for the great troubleshooting thread!
I just added it to my WB02 documentation. I will be building mine shortly and your tips and info will be quite helpfull!

Greg:hail: :hail:

1bad91Z

iTrader: (1)

Did you notice any peformance improvements after the WBo2 install? And if so, how much of a difference?

poncho@home

Why would he notice any performance improvements after a WB O2 sensor install? Unless you are asking if he got any valuable information that he used to change his fuel curve which then resulted in a performance impovement. I assume that's what you are asking?

Grumpy

The whole art of tuning changes with a WB.

While you can data logg all day long, having a WB with say a 40 dot LED display lets you seeeeee aallllll the transistional AE stuff in addition to knowing your WOT fueling changes are making a difference.

poncho@home

Yes I realize that the whole "art" of tuning changes with a WB O2...but the question sounded as if there would be improved performance from the result of simply installing one.

A WB O2 is my next project because it's the only way to tune for WOT correctly. But I don't see how just installing it will make a difference, and I just wanted to clear that up for those that don't realize that so they understand clearly what it is, it's not a performance improvement, it's an accurate tuning tool, that's all!