Car: 2004 Toyota Sienna LXE AWD Limited

Issue: intermittent check engine legit (every few months, only stays for a drive or two)

Codes:
P2238 - O2 Sensor Positive Current Control Circuit Low Bank 1 Sensor 1
P2241 - O2 Sensor Positive Current Control Circuit Low Bank 2 Sensor 1

I know O2 sensors go bad sometimes but with two of them showing that at the same time seems like it might be a legit problem? No apparent drivability issues. The code showed yesterday afternoon
On our way to dinner, but the check engine light was off this morning though it still read the codes the first time I started the engine. When I restarted the engine and read again there were no codes.

I’ve had two go bad on me at the same time. Also a Toyota.

It might just be a sensor glitch. I recently had the check engine light on my 2016 Sienna go off for a exhaust side timing issue. My blind spot indicator glitches all the time, especially when it’s very cold outside. I think something like 4-6 starts of the vehicle resets something with the check engine light so if there is no real issue or if the problem goes away the check engine light will eventually go off.

The system scans for issues constantly doesn’t it? If there was an issue the code/check engine light shouldn’t go away right?

If they’re original, it wouldn’t surprise me. I’ve replaced several over the years, some are easier than others. Just a matter of how much room you have to work with.

Recently went through something similar with my 2001 F150. Check Engine light would stay off until the truck reached a certain temp, at which point the light would show up again. If your Toyota is configured like my truck (which it likely is) "Sensor 1" is the O2 sensors in front of the catalytic converters ("Sensor 2" would be behind the cats). The sensors are easy to change and somewhat inexpensive (if memory serves, I bought mine off Amazon). Throw a new pair in, clear the code(s) and see if that solves your issue. My bet, it will.

Oh, and you'll need a special socket to remove the sensors you can borrow from your local AutoZone or Discount Parts store.

quote:

Originally posted by stickman428:
If there was an issue the code/check engine light shouldn’t go away right?

In my Ford F150, the check engine light would only illuminate for a bad O2 sensor when the exhaust system (i.e. the cats) reached a certain temp. Most of the time, the Check Engine Light would never come on when driving at night when it was substantially cooler.

May want to google and see if the anyone resolves it with the gas cap. I had a GX470 that the check engine light would come on occasionally too and then I swapped out a new cap and it was fine.

Odd for both to be faulty at same time, not that it couldn't. I would try changing the power relay that operates the O2 sensors heater, or check for a bad connection first.

quote:

Originally posted by Greymann:
Odd for both to be faulty at same time, not that it couldn't. I would try changing the power relay that operates the O2 sensors heater, or check for a bad connection first.

Is that in the fuse box?

I'm not familiar with your model but in the engine compartment, may be in fuse box.
Most have relays and fuses together in same box. I'll check and see if I can find out.

Yes in engine compartment in fuse box, take off lid and look at underside at fuse relay map, the one that runs your o2 heaters probably is the shown as A/F.
Wells relay #1R1696 shown at rock auto $5.00

This message has been edited. Last edited by: Greymann,

Bad gas?
Run a tank with some drygas through it.
If the O2 sensors can be found for a reasonable price, replace them. Also check that the gas cap seals are ok and that it's good and tight.

For o2 sensors, I have found that it is the one item that I buy OEM. I'm not saying aftermarket parts won't work, but that is one item I have seen time and time again need OEM.

I’ll start with the relay as it doesn’t get any easier than or cheaper than that. Will throw a new cap on it too later (after giving some time to see if the fault returns).

OEM (Denso, if I recall correctly) replacement sensors are just over $100 on rock. The bank 2 one would be a piece of cake, bank 1 seems like a nightmare to get to on a transverse engine. Will hold off on those. Just seems less likely they would both go out at the same time.

This message has been edited. Last edited by: thumperfbc,

quote:

Originally posted by Greymann:
Yes in engine compartment in fuse box, take off lid and look at underside at fuse relay map, the one that runs your o2 heaters probably is the shown as A/F.
Wells relay #1R1696 shown at rock auto $5.00

Thanks, I’ve located it. I’ll switch that out! Easy enough.

Consider putting some Cataclean in your fuel. Autozone may sell it.

quote:

Originally posted by rtquig:
For o2 sensors, I have found that it is the one item that I buy OEM. I'm not saying aftermarket parts won't work, but that is one item I have seen time and time again need OEM.

The dealer will want $150-200 per sensor. Go to Rockauto and see if Denso makes an O2 sensor. Chances are Denso was the OEM supplier for Toyota.

Toyota TSB EG001-05 calls for a recalibration of the PCM. It has a 96-month/80K warranty during which it is a free repair, but you've exceeded the time. Although these sensors look like O2 sensors and perform the same function, they are actually air-fuel ratio sensors; they work much different as well as cost more. Instead of generating a varying voltage they generate a varying current. The car probably has enough miles to where it may need these sensors, but you want to perform this recalibration first.

The above "courtesy" of Identifix.

quote:

Originally posted by egregore:
Toyota TSB EG001-05 calls for a recalibration of the PCM. It has a 96-month/80K warranty during which it is a free repair, but you've exceeded the time. Although these sensors look like O2 sensors and perform the same function, they are actually air-fuel ratio sensors; they work much different as well as cost more. Instead of generating a varying voltage they generate a varying current. The car probably has enough miles to where it may need these sensors, but you want to perform this recalibration first.

The above "courtesy" of Identifix.

Is that a dealer function only? We bought this car about a year ago so don’t know if it ever was done in the first place.

did you recently go to a valet parking? they get pissed at tips and leave your gas cover just loose, and you get a chk eng light. assholes.