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2003 Sienna - P0136 OBD code - have questions

Hi:

I have a 2003 Sienna with 99K kms. Recently, I had gone on a trip for 3 weeks. I left the gas tank almost full to prevent condensation and disconnected the -ve battery terminal to conserve the battery power. After coming back and driving the van, on the 2nd trip the check engine light came on. I got it scanned with an OBD2 scanner and got a P0136 (O2 sensor circuit malfunction Bank #1 Sensor #2). I've noticed that the gas consumption has increased significantly after this light has come on.

It seems that in almost all cases, the only resolution is to change the sensor.

I have a couple of questions:

  1. Is there a chance that some condensation/moisture due to not driving the van for 3 weeks may have caused this MIL light to come on "temporarily" and caused this code?
  2. Has anyone had success after clearing the code using the scanner tool and the light not coming back on? Can the code be cleared by disconnecting the -ve battery terminal?
  3. I spoke to the service manager of the dealership where I bought this van. He suggested that I should clear the code once and use a fuel system cleaner. He told me that this is the first step they do is to clear the code as it may be a temporary thing. I've added a bottle of "Fuel System Cleaner" to a full tank of gas. Would that help in cleaning the O2 sensor and maybe solve the issue? I'm thinking of driving for half a tank and then clearing the code so that the fuel system cleaner has taken some effect. If the MIL light still comes on with the same code, then I know for sure that I need to replace this thing.
  4. I understand that the connector for this sensor is under the front passenger seat. I've read in one of the threads that it can be accessed without removing the seat. Can someone please tell me where exactly would this connector be? And if the need be, how do I remove the seat to access it?

Thanks in advance.

Cheers.

AJ.

Reply to
AJ
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Possibly, but very unlikely.

If the trouble that made the MIL illuminate is still there, it will come on after the ECM detects the problem for 2 trips.

The code can be cleared by disconnecting the negative (is that what you mean by "-ve") terminal but as I said above, the MIL will come back on after 2 trips if the problem is still there.

I've never heard of fuel system cleaner working, but it shouldn't hurt to try. I recommend the Toyota brand stuff that Toyota dealers sell or Chevron Techron fuel system cleaner.

You can try looking under the vehicle for the O2 sensor after the catalytic converter that comes off of the cylinder bank closest to the firewall and see if you can reach it. Removing the seat is relatively easy - just remove the 4 bolts that hold the seat track in place and unplug any connectors for the power and/or heated seat, then place the seat in back so you can get at the sensor. There is probably an access cover under the seat that is held in place with Phillips screws or 10 mm bolts.

Before you replace the sensor, I'd check its function to make sure it is bad before replacing it.

Reply to
Ray O

Thanks for all the responses Ray O.

Your suggestion:

How do I make sure it is bad? The only pointer that I have at this time is the OBD code that indicates it "could be" bad. I've put in a bottle of fuel system cleaner and cleared the MIL once. I've driven about 60kms and it has not come back on. If the get the same OBD code after clearing the MIL once, is it not confirmation that I have to replace it?

Please advice.

Thanks again,

AJ.

Reply to
AJ

I also responded to his e-mail directly, but for everyone else's sake, I'll post here:

If you get the same OBD code after clearing the MIL once, there is a good chance, probably 80% or 90%, that the O2 sensor is bad. There is a slight possibility that the wiring between the sensor and the electronic control module (ECM) is bad or that the ECM itself is bad. Good luck!

Reply to
Ray O

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