Persistent P0136 O2 code after harmonic balancer failed

[jaketrimble]

1997 legacy 2.2

 

So my harmonic balancer came loose. in the process it shaved some metal off the balancer where it meets the crankshaft end. The crank was in good shape so i replaced the pulley and some time after I got the P0136 O2 sensor code.  I removed the O2 sensors to find dirty metal shavings clinging magnetically to both sensors (one by the oil filler neck one by the alternator).  I cleaned the sensors, cleared the code and some time (100s of miles) after had the code come back. I found more shavings, cleaned the sensors and again cleared the code.  Now I am getting the code but upon removal the sensors appear clean.

 

Questions:

1. why the persistent code even after cleaning the sensors? it doesn't come on immeadiatly after clearing but a dozen drives or so after.

 

2. should the O2 sensors be replaced?

 

3. am I missing an additional sensor to the two previously mentioned?

 

4. and most importantly, my timing belt has 40,000 miles only. is it compromised from the harmonic balancer fail and should it be replaced preemptively to avoid totalling the engine if it failed?

 

 

thank you!

[GeneralDisorder]

You're confused - the sensors you are talking about cleaning are the cam and crank sensors - the O2 sensor is the exhaust.

GD

[el_freddo]

If you have issues with your cam or crank sensors, you’ll usually experience engine cut out or loss of power. It would not be nice to drive if you could get it out of the driveway. 

If the code is actually the O2 sensor, you need to check this out. It’s located near the RHS driver shaft’s inner joint, but in the exhaust in front of the cat. You’ll see what looks like a probe with wires coming from it. That’ll be the O2 sensor. 

As for the timing belt. A visual inspection would be good. If you’re really worried just do it. 

Cheers 

Bennie

[ocei77]

You seem to have two concurrent but different issues.

The O2 sensor in the rear may need to be replaced, but first go through the diagnostic listed in the FSM .

http://jdmfsm.info/Auto/Japan/Subaru/

You will  need to remove the end covers and blow the main cover out thoroughly with air. There are still pieces floating around from the crank pulley.

 

O.
 

[jaketrimble]

Ok, so I was definitely confused about what those sensors were.   The more you know... Well, I just did a quick visual on the O2 sensor and found a frayed wire loose on the harness that the sensor connects to! So I'm guessing that's whats causing the code. Thanks for you help clarifying that one! If fixing that harness doesn't fix the code I will post back.  

 

I didn't realize the timing belt cover came off in multiple pieces (I thought I'd have to remove the other belts and whatnot in front of it), so I will take that off and inspect / blow out tomorrow.  Any other thoughts/opinions on timing belt lifespan shortening considering the shavings from the harmonic balancer? Thanks for the replies!

[ocei77]

You can pull the balancer and timing cover to inspect the belt for embedded metal and put back.

If you find defects in the belt, plan on replacing as soon as feasible.

O.

 

[1 Lucky Texan]

if the bearings for the toothed idler are failing, that could be a source for magnetic debris too.