Can You Solve This CEL O2 Sensor Riddle?

Hey Bob. These are the one's you'll need for the downstream when using longtubes.


CONN-85837 4 Way Extension for Subaru & Toyota Oxygen Sensor

https://www.bmotorsports.com/shop/product_info.php/products_id/3244

The upstream extenders are not necessary.

 

its page 2 now, all bets are off.

somewhere theres a link to a downloadable factory service manual. Or bug bubbaw or shifty. Pretty sure they have it memorized. A couple of my coils also had some brown tint to em and 1 has a crack down the length, but *knock on wood* i havent had any trouble yet.

 

Even tho your 05 is a Sequoia, it’s firing order is same as Tundra. Prove it further if still insure of answers here and unplug driver side # 1 cylinder ignition coil and see what code appears.

 

I do have an 05 Sequoia FSM but never learnt how to put it somewhere for downloading

 

My coils are still good. You should get misfire codes if yours aren't. Others may argue, but I feel like it's pretty binary on those.

 

Replaced plugs with Denso TT iridiums, cleaned my older long life Densos that could be fake by soaking in seafoam and they look good too.

Probably placebo but it's driving and idling much better. CEL still persists. I have made a new discovery though. The driver side bank A/F sensor harness cable will absolutely not clip in no matter how hard I press. Also discovered a tiny exhaust leak.

I cannot replicate the sinewaves as mentioned on page one through my OBD tool.. I'm going to take it to an exhaust shop to fix the leak and see what they could do about the cables. Then off to the crusher.

 

It's a 2005, and I apologize. You will need one extender for the upstream on the drivers side, and its a different connector.

This is it:

https://www.bmotorsports.com/shop/product_info.php/products_id/4047

So one of those^ and two of the other ones I posted earlier.

 

Exhaust leak fixed. CEL prevails. I'm beginning to think that the O2 extenders are weakening the signal which is why I'm stuck with these low heater circuit codes. P0031 and P0051. Also could be the placement of the AF/O2 sensor on the headers themselves.

Truck is running great though. Oh well, looks like I'm part of the CEL 4 life club.

 

Just so we are on the same page with thoughts....few questions, followed by comments.

1) Codes 31 and 51 both come back simultaneously after reset or 1 or the other comes back according to what bank their in ?
2) You indeed have checked underhood the A/F relay along with the 20A A/F fuse ?
3) Confirm you indeed installed the A/F sensors in collector or did you mean primary ?
4) You mentioned earlier "cut wires"....did they cut the A/F sensor wires or harness portion going to ECU ?
5) After reset of codes, you have no other codes besides 31/51 and no other abnormal lights other than check engine ?

Heater circuits of O2's are pretty straight forward....the heater circuit either has the proper resistance when bench tested or they don't. When they are hooked up, the ECU supplies current to 1 pin of sensor and the other pin either has bat 12vdc or it don't

 

1. Yes, same time.
2. Yes, checked and even swapped fuses/relays to no avail
3. Primary/First hole
4. They cut just the wires. The harnesses were still plugged in, just exposed pig tails (could this have shorted something? hmm).
5. Yes correct. Only those two codes and the VSC/Trac lights on.

 

When I got my ARH setup they came with extenders and Nick mentioned to only use those as any others could cause a CEL. I have read elsewhere also that extenders are so finicky. Voltage loss etc

 

Yep, this is what I'm chalking it up to. The wires are very sensitive and running longer wires weakens the draw I'm sure at this point.

 

No grease, and the extender for the AF is only on the driver side. The rear downstream O2's both using extension with no issues.

 

Which means the pass side should not be affected by "wires are very sensitive and running longer wires weakens the draw"....simply thinking over coffee. With that info about pass side A/F sensor not having a extender, circles me back to what was mentioned earlier.

"the ECU supplies current to 1 pin of sensor and the other pin either has bat 12vdc or it don't"

If your Sequoia is like our Tundras, checking pin 2 of the A/F sensor is difficult but doable. That said, I would suggest unplugging B2S1 and check for 12vdc to GND at pin 2 of Bank 2 Sensor 1 with ING ON/EG OFF. According to an 05 Sequoia FSM and EWD, pin 2 of B2S1 is Red-White in color.

If no 12vdc at pin 2 of either sensor, the items to double check that would prevent lack of 12vdc at pin 2 of both A/F sensors are EFI Relay, EFI No. 1/EFI No. 2, A/F Relay and A/F fuse. You can only hope it's not the ECU side of A/F sensors.