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01 subaru legacy outback replaced upstream o2 sensor check…

Customer Question
01 subaru legacy outback...

01 subaru legacy outback replaced upstream o2 sensor check engine light keeps coming back on tried to reset comes back on?

Mechanic's Assistant: Does the light stay on, or does it blink?

I turned off with scanner and comes bass on?

Mechanic's Assistant: Are you fixing your Outback yourself? What have you tried so far?

Yes it keeps reading the same code 1132 and a/t temperature light keeps blinking.

Mechanic's Assistant: Anything else you want the mechanic to know before I connect you?

Would it be a ecu problem?

Submitted: 5 months ago.Category: Subaru
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Answered in 12 minutes by:
3/14/2018
Subaru Mechanic: Jim, ASE Certified Technician replied 5 months ago
Jim
Jim, ASE Certified Technician
Category: Subaru
Satisfied Customers: 1,524
Experience: California smog licensed, ASE ceritied in L1, A6, A8 for over 30 years professionally
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Hello and welcome.

My name is ***** ***** I will be assisting you today.

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Subaru Mechanic: Jim, ASE Certified Technician replied 5 months ago

They use a relay to supply 12 volts to the sensor have you checked to make sure you are getting 12 volts to cavity #2 on the sensor.

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Customer reply replied 5 months ago
How'd I can check it?
Subaru Mechanic: Jim, ASE Certified Technician replied 5 months ago

Disconnect the sensor start the car and use a volt meter or test light and check for 12 volts with meter or test light will light up with 12 volts on that wire, you are check the wiring harness side.,

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Customer reply replied 5 months ago
What color wire?
Subaru Mechanic: Jim, ASE Certified Technician replied 5 months ago

The diagram doesn't show color only cavity, only 1 of the 4 wires will have 12volts.

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Customer reply replied 5 months ago
There's power from the ecu
Customer reply replied 5 months ago
What would I check next?
Subaru Mechanic: HighwayRepair, Subaru Technician replied 5 months ago
HighwayRepair
HighwayRepair, Subaru Technician
Category: Subaru
Satisfied Customers: 665
Experience: 8 Years Auto Repair Experience. Owner/Operator of Highway Auto Repair, a mobile automotive repair business
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Hello online007. My name is ***** ***** I can help you fix your issue. Can you clarify two things for me please since you were working with another expert already:1.) you haven’t replaced any parts yet.2.) there is 12 v between pins 2 and 4 going to the oxygen sensor (this is important that you use both pins for the test, as this will check the power wire going in and the ground wire going in). Using the chasun or battery negative terminal as a replacement ground and only checking one wire for power is not a proper test imho.
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Customer reply replied 5 months ago
I've replaced the upstream 02 sensor
Subaru Mechanic: HighwayRepair, Subaru Technician replied 5 months ago
Ok great. And when you checked for power did you check directly at pins 2 and 4 of the oxygen sensor? (It’s important that you used both of these wires to test.
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Customer reply replied 5 months ago
I checked wires from the. ecu they have power
Subaru Mechanic: HighwayRepair, Subaru Technician replied 5 months ago

does the sensor you are testing have 4 wires, or 6 wires connecting to it?

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Customer reply replied 5 months ago
6
Subaru Mechanic: HighwayRepair, Subaru Technician replied 5 months ago

ok great. so this is an "air fuel meter" not an oxygen sensor, but a very similar part. The sensor itself is usually the problem with these, but you have replaced that already. There was a recall for the engine computer for the year before your vehicle for this issue, but that doesn't apply to your car.

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Subaru Mechanic: HighwayRepair, Subaru Technician replied 5 months ago

How long after you turn the light off with your scanner, before it turns back on?

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Customer reply replied 5 months ago
Immediately a few seconds.
Subaru Mechanic: HighwayRepair, Subaru Technician replied 5 months ago

Very interesting. This leads me to think the problem is not in the logic circuit of the sensor or the computer, but definitely in the power/ground circuit. If its just a few seconds, the car is not seeing a reading of air/fuel that it doesn't like and throwing a code. It most likely simply isnt seeing a reading at all. Looking at the wiring diagram again, because you have an automatic transmission ( and therefore the six wire sensor). the wires are different

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Subaru Mechanic: HighwayRepair, Subaru Technician replied 5 months ago

we are looking for 12V between pins 2(yellow/red wire) and 5(solid yellow wire). I am betting you do not have proper signal on those wires. can you verify that. earlier you agreed you had power on wires 2 and 4.

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Customer reply replied 5 months ago
Power on red and yellow no power on the solid yellow.
Subaru Mechanic: HighwayRepair, Subaru Technician replied 5 months ago

you are checking for a 12v differential between those two. so set the volt meter to voltage, and put one probe on one wire, and one probe on the other wire. this will check for both power and ground

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Subaru Mechanic: HighwayRepair, Subaru Technician replied 5 months ago

*I want you to check for a power differential between those two wires, not " you are".

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Customer reply replied 5 months ago
11.86 with just ignition on and 13.65 with the car on.
Subaru Mechanic: HighwayRepair, Subaru Technician replied 5 months ago

that voltage reading is perfect. do you have a high resistance test light by chance? ( to check for amperage?)

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Customer reply replied 5 months ago
I have a test light don't if it's high amperage.
Subaru Mechanic: HighwayRepair, Subaru Technician replied 5 months ago

"High resistance" is what we're looking for. Is it relatively new? most of them are.

Does it look like this? : https://www.amazon.com/Professional-6-12V-Circuit-Tester-Industrial/dp/B003UHNMMS

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Subaru Mechanic: HighwayRepair, Subaru Technician replied 5 months ago

try this then, this will check for a loose/corroded connection, and also one of the common ways computers fail

unplug the oxygen sensor, and put one end of the test light on pin2, and the other end on pin 5. If the test light turns on, we know you have proper amperage.

It is completely possible to have proper voltage, but lose amperage due to a bad connection.

you may want a second sec of hands, the car may stop supplying power to the connector by choice after a few seconds of seeing the car on and the connector unplugged. So it can be nice to have the test equipment set up already, and have a second person turn the car on.

Make super, double, triple, sure this is completely safe before you try it. super dangerous to be on/under/around a running car for testing.

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Subaru Mechanic: Amedee, Automotive Consultant replied 5 months ago
Amedee
Amedee, Automotive Consultant
Category: Subaru
Satisfied Customers: 27,978
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Phone call session started
Customer reply replied 5 months ago
Power only to the red and yellow no power to the yellow.
Subaru Mechanic: HighwayRepair, Subaru Technician replied 5 months ago

I'm not sure what your last reply means. when you put one end of the test light on pin 2, and the other end on pin 5, does the test light light up?

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Customer reply replied 5 months ago
Pin 2 is the red and yellow wire pin 5 is the yellow wire
Subaru Mechanic: HighwayRepair, Subaru Technician replied 5 months ago

when you put one end of the test light on pin 2, and the other end on pin 5, does the test light light up

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Customer reply replied 5 months ago
it turns on
Subaru Mechanic: HighwayRepair, Subaru Technician replied 5 months ago

thank you. this verifies the wiring to the oxygen sensor is proper, and eliminates poor connections as a possibility.

Is the replacement oxygen sensor a factory part or an aftermarket one? At this point we have verified the wiring is ok. The problem is most likely either a faulty air fuel sensor was delivered to you out of the box ( unfortunately this does actually happen), or a bad engine control module. Due to the high cost of an engine control module, I would remove and replace the air fuel sensor again, using a factory part. These broad band air fuel sensors can be very finicky with aftermarket variations.

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Subaru Mechanic: HighwayRepair, Subaru Technician replied 5 months ago

if it took longer for the light to turn back on there would be potentially other issues, but because the light turns on so fast, it is very likely either the sensor itself or the control module

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Customer reply replied 5 months ago
Its been. replaced twice
Subaru Mechanic: HighwayRepair, Subaru Technician replied 5 months ago

With a factory part? cheap aftermarket parts do not work well for this type of broad band air fuel sensor.

If you are using a factory part, your problem is almost guaranteed the ecu itself

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Customer reply replied 5 months ago
Bosh 02 sensor
Subaru Mechanic: HighwayRepair, Subaru Technician replied 5 months ago

the direct fit one with a connector already attached? or the cheaper version with just bare wires on the end? ( Bosch makes both versions for this car)

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Customer reply replied 5 months ago
Direct fit
Subaru Mechanic: HighwayRepair, Subaru Technician replied 5 months ago

Those are very good parts. It is highly unlikely you got two bad ones in a row, and with the testing you have performed on the wiring, and the fact that the light comes back on immediately, you are almost assuredly looking at a bad engine control unit.

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Subaru Mechanic: HighwayRepair, Subaru Technician replied 5 months ago

I want to make sure you've exhausted all possibilities to your content. Is there anything else I could help you with?

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