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P0136 - Oxygen O2 Sensor Circuit Low Voltage (Bank 1, Sensor 2)


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Yeah, big thanks to SubaruFred for the exhaust leak. His suggestion and the $50 I spent to get it fixed probably has saved me hundreds of dollars in gas.

 

Here's the other issue- the gas meter is off. I have a 16 gallon tank, but when it's down to E and I fill the tank I only get about 11 gallons in, which means there is 5 gallons still in there. Should it read E at 5 gallons? Any way to recalibrate the gas meter?

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This is a pretty common problem. There are two sensors in the tank and it sounds like one of them isn't working correctly. Some folks have used Techron in the tank to clean the contacts and had success. It may tank a couple of tanks and bottles to allow it to work. Seafoam may work also. Otherwise you will need to remove them.

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Update:

 

CEL is back, complaining of bank 1 sensor 1. Turns out you need to ignore "bank" and instead focus on sensor. The rear sensor, in the second cat, is broken. Snapped in half. The front sensor is fine as it's new and OE.

 

So, what should I replace the rear sensor with? I understand it does not need to be OE, but I do not want to be splicing. Suggestions?

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The OE o2 sensor is $136 and the NGK one is $90something. Any suggestions? Remember, this is for the secondary cat.

 

the rear o2 sensor can be generic buy the cheaper one.

 

but it does not make sense to me that the rear sensor failure would cause the p0136 code on the front sensor. but if the rear is busted it should be replaced.

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Today's saga:

 

Got the following O2 sensor from Advance Auto Parts for $98.99: http://shop.advanceautoparts.com/webapp/wcs/stores/servlet/product__18470480-P_291_R|GRPEMISAMS____?cm_mmc=ET-_-Trans-_-Confirmation-_-General They are having a sale where if you buy $100 or more online and put in the code you get a $50 gift card. I also bought some engine degreaser so now I have a $50 card coming to me!

 

I also bought a 7/8" O2 sensor tool, went into the parking lot, jacked up my car (used jack stands, also) and went to town. That darn thing wouldn't budge. It was really, really rusted on and in no good shape. I ended up yanking the old O2 sensor's wires off and it still wouldn't move. I ended up rounding it and gave up. I returned the tool and went to a garage down the street. The guy there charged me $25 to swap the O2 sensor. He had to use a blow torch to get the old one out.

 

Considering the tool cost $18 I think spending $25 to have a garage do it was just fine.

 

I reset the code and will fill the tank in the morning (I'm at empty) and I hope and pray this goes away for good.

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  • 4 weeks later...

Code has come back for Bank 1, Sensor 1. I was driving from Montreal to Boston and it came back outside of Burlington, VT. Stopped in Burlington and cleared the code, but it came back almost exactly 50 highway miles later. I was able to drive from Boston to Montreal with no codes, then the car sat for 3 days while I visited with friends. I am thinking it might be the converter, so tomorrow I am going to my friend's garage to replace it. I have another converter in my trunk (direct fit) and will see if that might help. Will also check the O2 sensor connections and make sure it's fitting tight and well.

 

Any other ideas?

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I doubt changing the CAT will make any difference for a low voltage code. The trouble sounds like there is a bad connection between the sensor and the ECU. A high resistance in the line will cause a low voltage to be seen by the ECU.

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I doubt changing the CAT will make any difference for a low voltage code. The trouble sounds like there is a bad connection between the sensor and the ECU. A high resistance in the line will cause a low voltage to be seen by the ECU.

 

Excellent point. V=IR, I have to remind myself. If R is high, then V is low assuming I (amp) is constant. So, any ideas how to check for a bad connection?

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Measure the resistance between the two points. A good connection will have less than 1 ohm of resistance.

 

I'll do that tomorrow. It's odd, tho, in that this is a new OE O2 sensor. I put this one in when I got the original code.

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Before anything I decided to scan the code again. It is no longer reading as P0136 but is now reading as P0130 "DTC P0130: FRONT OXYGEN SENSOR CIRCUIT MALFUNCTION". Do you think I should still check the resistances?

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A circuit malfuction means there is a problem with the connection to the sensor. It could be due to a short or open connection on the wire to the sensor, a bad connection, or a bridged connnection to something else that shouldn't be tie to the circuit. You need to test the wire connection for these kinds of problems. Having a meter to do that with is necessary. This is with the front sensor though not the rear one.

Edited by Cougar
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The trouble is with the circuit to the sensor. Unless the wiring on the sensor has been damaged then the trouble is in the external wiring to the sensor.

 

You mean with the wiring connected to the sensor or the wiring where the sensor wiring plugs into?

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The wire connection between the ECU and the sensor.

 

I was afraid you were going to say that. It's a long wire with a lot of twists and turns. I'll replace the sensor and hope that resolves the issues. If not I'll hunt the wire.

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