99 V70 P0137 replaced sensor still low

donis222 · Post by **donis222** » 04 Sep 2014, 13:27

(P0137) I replaced the rear sensor and got the same low volts as before. When hot the V barely passes .5V. After checking ground wire for continuity (1.7 0hms), I think my next step is to rewire the signal wire; anyone have any other thoughts? I would try another sensor, but the voltage appears the same.

Post by **timmybdaddyof3** » 05 Sep 2014, 05:53

1. are your voltage readings from the sensor itself or from the odb2 port (i would piggy-back the connector to verify)
2. an oddity i noticed on mine (98 v70 t5 auto) after resetting the computer i got both a low voltage and slow to respond for about the first 50 miles...then they went away on their own (literally as i was on my way to buy a new 02 sensor)

Post by **JDS60R** » 05 Sep 2014, 16:07

Where are you measuring 1.7 ohms on the ground wire, ( Ground wire to chassis? battery neg term, body of sensor or between signal and ground wire)?

Please let us know what wire are you getting .5VDC on. This is mid stream result for the rear O2 but you should see different results once the car is in closed loop and should certainly see higher voltage when accelerating.

If the sensor is quality, new and heated up and you still can get only .5 volts on the signal wire then its time to look at fuel trims so you can determine air leaks, bad MAF or bad front O2.

You can heat an O2 on the bench and then feed it unlit propane to watch it work(change signal voltage). At some point we need to see the new sensor go over .5vdc so we know its not defective.

If your car has an air pump or EGR you would want to check them as well for leaking in the extra air that may be causing your lean condition. If your front O2 is over 100K miles in service you should replace it as its accuracy would be in question.

Do you have a scanner to see the results? (switching time on O2's, fuel trims under load vs idle etc)If you do let us know the results.

Post by **JDS60R** » 05 Sep 2014, 16:40

Not sure if you had a NA, LPT or HPT V70.

Here is some light reading on the sensors.

donis222 · Post by **donis222** » 22 Sep 2014, 16:51

First, thank you JDS60R for these files. I knew that the Denso O2 sensors were different than 98 and earlier V70 and 850's. I was hesitant to buy this '99 as I was getting into a different tech.
Second excuse me for not replying sooner. I had a spinal cord surgery problem that had me in the hospital for 5 months. I am pretty much recovered; but I won't be working much anymore.
The V70 didn't fix herself during my absence. I printed out the pdf's and am studying them. UHG!
I found a broken MAP vacuum hose. I am going to reset the adaptive fuel map and pray.

donis222 · Post by **donis222** » 23 Sep 2014, 17:55

Prayer unanswerred. The voltage is low coming from the ECM.
Gonna try replacing it next. PicknPull.

donis222 · Post by **donis222** » 23 Sep 2014, 18:20

FYI: Both LTFT and STFT are near 0!

donis222 · Post by **donis222** » 25 Nov 2014, 16:27

After checking every component and a thorough search for a vacuum leak and much hair pulling, I saw that the front sensor was working, but maybe low. The front sensor with Denso fuel management is different than the rear (Zirconium, I think. The rear is the same as an 850 or '98 S or V70.
I bought the Denso and the low S2 voltage is gone. It looks like the front was bad, but not bad enough to throw a code.

Post by **erikv11** » 25 Nov 2014, 16:59

Nice pickup, glad you figured it out. And thanks for posting the solution.

donis222 · Post by **donis222** » 08 Dec 2014, 09:04

I have never taken my personal car to a mechaninic since 1964. That time I realized the mechanic ripped me off, but I may be going to one soon. If I weren't retired, I would have done so by now.
I am still messing with the same problem. (The new O2 sensor changed some after a few miles. This may have been due to the aquired profile.)
The .pdf's are very interesting and very important to understand the difference in the fuel management between the Bosch and the Denso. In the last pdf.file, I read page 2 of 3 many times and can only conclude that there is decimal points missing.?
In my search for the answer, I found the following.
http://testroete.com/car/Toyota/mr2%20s ... rol/19.pdf
This very well done tutorial should be on everybody's list that plan to diagnose Denso's Fuel Management syatem.
More later.

Thanks to all who have helped.