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P0037 o2 Sensor Heater voltage low

Old 07-29-2012, 09:59 PM
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AZ P0037 o2 Sensor Heater voltage low

Hey guys-

I have a P0037 code for Bank 1 Sensor 2 (o2 sensor after the cat) heater voltage low. Just replaced my OEM cat with a Magnaflow cat/midpipe and reinstalled the original o2 sensor. It was coming back with this code, so I assumed something happened to the o2 sensor along the way. Today, I replaced it with a used o2 sensor, cleared the code and CEL is back with the same code.

While its possible this new(used) o2 sensor could have a bad heater, I feel its unlikely. I will have to double check the wiring now and see if there is a problem there. Was just wondering if anyone else has run into this code where replacing the sensor itself didn't resolve the problem.

Any advice would be appreciated.
Thank you,

Michael
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Old 07-29-2012, 10:04 PM
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bad 02 sensor!, or no 02 sensor is the cause but you're fine. it happens when you run catless pipe.

It will probably go away after the ECU gets used to it do a few drive cycles.
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Old 07-29-2012, 10:30 PM
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My midpipe has a catalytic converter though... You think both o2 sensors have the same problem with their heater? One thing I noticed as well is that if I clear the code, if I turn the ignition on just after it was cleared, that same code is already pending and will turn the light back on the second time the car is started.
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Old 08-06-2012, 08:23 PM
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Anyone know any specs for this oxygen sensor? I'll have to get out the multimeter this weekend but don't know what specifications the sensor/wiring needs to be at?

Anyone that can help?

Thank you in advance,
Michael
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Old 08-12-2012, 01:57 AM
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For anyone that cares, or more importantly, those that have this DTC in the future. I measured my old o2 sensor and the used o2 sensor for resistance on the heater. No voltage at all so apparently the used o2 sensor I bought was junk. I purchased a universal o2 sensor from O'Reilly's, installed and the code has not come back yet today.
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Old 04-08-2013, 04:32 PM
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Ive replaced both my sensors. But I still get codes p0037 and p0138 ! Not sure what do to.
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Old 04-08-2013, 10:47 PM
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If you have replaced the sensor and the code is still present follow these steps.

1. Remove rear O2 sensor connector inspect for poor connection (such as damaged/pulled-out pins, corrosion) since the sensor has been replaced check harness side.
2. Measure the voltage between rear HO2S terminal D (wiring harness-side, bottom left wire from rear of connector) and body GND with Key On. Is the voltage B+? Yes: Repair or replace the wiring harness for a possible short to power, clear codes and retest.
3. Inspect PCM connection (such as damaged/pulled-out pins, corrosion), if good clear codes, if codes return replace PCM.

Hope that helps

Braden
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Old 03-26-2015, 11:14 AM
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I'm getting two P0037 codes. Both read HO2S Heater Control, Crct low bank 1 sensor #2
I checked my wiring and it's all good so I figure it is the rear O2 sensor.
Is the code for the front O2 sensor different?
Why am I getting two exact codes?

I'm getting two P0037 codes. Both read HO2S Heater Control, Crct low bank 1 sensor #2
I checked my wiring and it's all good so I figure it is the rear O2 sensor.
I can erases the codes but they come back together on the next drive cycle.
Is the code for the front O2 sensor different or the same as the rear O2 sensor?
Why am I getting two exact codes?

Originally Posted by Jon316G View Post
You are correct, P0037 is the rear O2 sensor. I would make sure that the connector is fully connected, but it will more than likely need replaced.
I'm getting two P0037 codes. Both read HO2S Heater Control, Crct low bank 1 sensor #2
I checked my wiring and it's all good so I figure it is the rear O2 sensor.
I can erases the codes but they come back together on the next drive cycle.
Is the code for the front O2 sensor different or the same as the rear O2 sensor?
Why am I getting two exact codes?

I'm getting two P0037 codes. Both read HO2S Heater Control, Crct low bank 1 sensor #2.
I can erases the codes but they come back together on the next drive cycle.
I checked my wiring and it's all good so I figure it is the rear O2 sensor.
Is the code for the front O2 sensor different or the same as the rear O2 sensor?
Why am I getting two exact codes?

Originally Posted by GK1707 View Post
Also the check engine light indicates low voltage at the front o2 sensor so I'm not sure if thats whats causing the battery light or is the alternator I just bought bad. Anyone have this problem?
not trying to hijack here but I would like to ask what the code for the front O2 sensor is.

Originally Posted by Sh00bs View Post
threw a 02 sensor code. have emissions coming up VERY soon. car still runs fine, just need to get rid of this code. if you have a pair that you know both work, help a fellow rotard out shipping would be to 21122
Hi.
I'm getting two P0037 codes. Both read HO2S Heater Control, Crct low bank 1 sensor #2.
I can erases the codes but they come back together on the next drive cycle.
I checked my wiring and it's all good.
This code is listed to the rear O2 sensor. But the fact that I'm getting two codes leads me to question if the front sensor is bad as well.
Is the code for the front O2 sensor different or the same as the rear O2 sensor?

Last edited by RIWWP; 03-27-2015 at 07:01 AM. Reason: posts merged
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Old 03-27-2015, 06:49 AM
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2? u mean pending and freeze frame

front and rear OF COURSE they are different
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Old 03-27-2015, 07:03 AM
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Bank 1 sensor 1 = front
Bank 1 sensor 2 = rear
Bank 2 or higher = you are driving a different car
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Old 03-27-2015, 07:37 AM
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The only thing that matters is the DTC Code number. Anything else is irrelevant. Take that code number and look it up here:

http://www.revolutionrotorclub.com/f...ne_Control.pdf


Then page down go to the troubleshooting section for that code. P0037 troubleshooting starts on indicated Page 27. As stated, the P0037code is for Rear H2OS Heater Circuit Low. It tells you everything you need to know. However, you need a *known* good O2 sensor. Buying a used one you cannot always be 100% sure if its good or not depending on the situation (like a friend who took it off and it was fine then vs some person of unknown reputation on the internet).
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Old 03-27-2015, 02:29 PM
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Thanks to all.
I actually found the list and the two different codes for the front and rear sensors.
I still don't know why I'm getting two P0037 codes on my code reader.
I do not know "pending and freeze frame".
I only know that I get two codes at once. I clear them and they stay gone till I restart the car.
Then they return, together. One of two and two of two. Both P0037.
Has me hesitant about getting a new sensor if the problem could be something else.

Last edited by titaneum_grey; 03-27-2015 at 02:34 PM. Reason: Removed Redundant Sentence
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Old 03-30-2015, 08:36 PM
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if ur ecu works and there is no wiring problem. get a new one.

the sensor goes slow (on its way to death) around 40-50K miles anyway, and replacement cost like what, 100 ish bucks? just replace it
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Old 03-31-2015, 03:44 PM
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in my search for an 04, Rear O2 Sensor.
Part No. N3H3-18-861B I have found on line
NEW BORG WARNER BWD 4W OXYGEN SENSOR MAZDA VEHICLES VARIOUS (Fits: Mazda RX-8)
$17:50
13772 234-4349 Oxygen Sensor Downstream for 2004-2008 Mazda RX-8 (Fits: Mazda RX-8)
$20:99
04 05 06 07 08 Mazda RX8 1.3L Rear Oxygen Sensor O2 N3H218861C9U 2344349
$56:95
04 05 06 07 08 Mazda RX8 1.3L Rear Oxygen Sensor Standard 6 Speed Bosch O2 NEW
$75:00
04 05 06 07 08 Mazda RX-8 1.3L Front Oxygen Sensor O2 NEW 15043 (Fits: Mazda RX-8)
$86:00
04 05 06 07 08 Mazda RX8 Rear Oxygen Sensor O2 NEW 22506 NEW
$90:23
And the dealership wants $204.
SMH
What is the difference?
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Old 03-31-2015, 07:01 PM
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if i were u I will go for something mid range, Bosch is fine for Rear O2, or Walker
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Old 07-12-2015, 12:09 PM
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i have just got a rebuilt engine and i installed it myself and i am getting a P0037 and a P0172, the car will not hold an idle ive replaced the front o2 and it helped till it fouled out. so i replaced exhaust and upper intake gaskets, also i have new maf and its still running rich. i have an aem intake and a bhr mid pipe and have deleted my air pump, i also have bhr ignition coils. i can not figure out why its running rich and stumped and frustrated ive got about 300 miles on the rebuild
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Old 02-23-2018, 08:00 PM
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sorry if this is necroe'ing a old thread...

I may be being paranoid here but i have been running catless for quite a while (2 years or so)
previously i was just getting a P0420 code which no issue really since i lost no power or MPG.
now recently i got a tuning program and told my ECU to stop checking for that code all together which made the CEL go away for a while then about 20 miles later it popped again

after i scanned it again i now have a P0037 code which is still just the rear O2 sensor that isn't there an still isn't putting me into limp mode or affecting my MPG any. my main concern is if this will cause an issue in the future of if i can just tell the ECU to stop scanning for this one aswell and continue on my merry way as usual

any input would be appreciate from people that understand the sensor and ECU safety protocols better than i do
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Old 05-02-2019, 12:38 PM
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The same thing i have with mine. I delete the code p0037 and after i start the car again the check engine light is on with the same code. I have all original pipes and catalitics. I think are the wires that make the problem or the connection. I took out the ensor i check everything and i put it back again. I tarted the car and the same code is on. I changed the sensor with new one and again the same code. P0037.
also if it runs for some time or some kilometers sonetimes as u drive it looses power and the engine goes off. Have to wait so not to flood and start it again. After 30 or more minutes is ok.
i dont know maybe is the oxygen sensor again.
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Old 05-02-2019, 03:33 PM
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If it loses power, stalls and doesn't restart until it cools down either your fuel pump is dying or your engine is dying.
Which sensor did you replace? P0037 refers to the one in the catalytic converter. If that's the one you replaced, then yes, the problem is somewhere in the wiring to it.

Is the car on its original engine? If you ever had the engine/transmission out, it's not unusual to damage the O2 sensor wiring when putting them back in.
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Old 05-03-2019, 01:01 PM
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Yes i replaced the upstream sensor first time that was onother code and for 2 years it was very good no code engine power ok everything.
After the check engine light was on and the code p0037. I changed the downstream sensor but the check engine is still on and there are alot of problems when the car is hot. After driving for 30 minutes or some kilometers around 15 and more looses power the rpms goes down less than 500rpm
And the car sometimes if u stop at the lights is the engine off and u cannot start it after because it will flood. So u have to wait more than 30 minutes and it starts again normal. I changed coils, sparks, wires, sensors. There is no other check engine code. Only p0037.
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Old 05-03-2019, 03:06 PM
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Easy way to check is to see if your car has trouble revving to high RPM.

If your car struggles to accelerate to higher RPM, it's the fuel pump.

If your car feels just fine when accelerating to higher RPM, your engine could be the problem there.
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