P0031 & P0051 - Upstream HTR O2 Sensor Bank 1 Sensor 1, Bank 2 Sensor 1 (3 Viewers)

[hortandr]

Well, it is with heavy heart and dirty hands I am writing this post. I am looking for any advise on how to proceed with an issue I have been unable to resolve.
2006 LX470
About 2-3 months ago when bragging to my friend about clearing a P2440 SAIS code that had me stuck in limp mode he noticed my check engine light was still on.
When I plugged in my reader I received a P0031 and a P0051 code.
P0031: HO2S Heater Control Circuit Low (Bank 1 Sensor 1)
P0051: HO2S Heater Control Circuit Low (Bank 2 Sensor 1)

Today while at work I decided I would take a stab at finding a solution.
I already ordered 2 upstream sensors in case I needed to replace these.
I took my DS sensor off. and decided I would test the resistance. I got back 2.6 on my multimeter and then compared to my new sensor. I got the same reading, 2.6-2.7.
I am no electrical engineer but my theory was that this means the sensor works.
I put the old sensor back in and decided to fiddle with the Relays and fuses. I had previously checked the fuse and it was fine, I still ended up swapping the 15A fuse with a spare 15A fuse.
I removed the relay and removed an equivalent relay from the fuse boxes. I followed a tutorial on how to test a relay but I was not sure if I did this correct.
I got bombarded by a contractor at work right after this so I am unsure of my values. I believe I got 175 Ohms when checking the resistance. I remember this value being the exact same for both relays.
I ended up swapping the DS HO2S with the new sensor as a Hail Mary.
My CEL came right back on unfortunately. I am still reading P0031 & P0051.

What could cause both codes to throw at the same time?
ECM issue?

I may replace Relay as there is a chance I was reading incorrectly.
If there are already posts on this issue I apologize. I did not find any so I decided to make one.

 

[2001LC]

Any work or mod to engine or wiring, including under the dash.

Windshield factory or replacement. Replacements, often result in water entry into cabin. Which, water can get to EMC and it's wires.

I'd check continuity of the wires harness to/from A/F sensors.

Since you had a P2440. I'd first check for vacuum leaks. Check the SAI vacuum lines first.
I'd also check to see if SAI filter is intact. Easiest way, is with a borescope.

S.A.I. Filter Modification, in VVT engines. To prevent its failure! Alert Alert!

We've a $2.00 part in the S.A.I. (secondary air injection) system of the VVT engine, that is taking-out ~$7,000.00 $15,000 $25,000 (inflation) in parts. WOW! I've a very easy and cheap WORK AROUND. You are going to love this ;) This thread is dedicated to the 4.7L 2UZ-fe VVT engine, in the...

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[hortandr]

Thanks, 2001LC. My windshield is factory to my knowledge. I have no records of it being replaced previous owner kept her at dealership for maintenance so I doubt they would not have a record.
I added a Bt45 Toy like day one of having the LX but this issue didn't start until a month or so later.
I have never checked for vacuum leaks before so I will be consulting the 'old heads' at work.
from what I can gather about this truck is it sat for long periods of time, most likely all winter outside. I have seen evidence of rodents in the engine bay. I wonder if this could be related.
I have access to a bore scope at work I will try and check out this filter integrity. I have an absolute bugger job of black silicon holding a hose into my intake manifold that I did not notice until after I had purchased the truck. I will have to replace the intake manifold soon as I am not comfortable going into winter like this. that would be a perfect time to work on SAI if I do need work to be done.

As always I appreciate your insights. I will report back with my findings!

 

[2001LC]

Thanks, 2001LC. My windshield is factory to my knowledge. I have no records of it being replaced previous owner kept her at dealership for maintenance so I doubt they would not have a record.

Inspection glass and how molding installed. One can usually determine, if replacement.

I added a Bt45 Toy like day one of having the LX but this issue didn't start until a month or so later.

I agree, not likely it now is and issue.

I have never checked for vacuum leaks before so I will be consulting the 'old heads' at work.

Make sure the vacuum lines are on both rear SAI SW. The VSV is on BK2 attached to intake manifold. One lines comes from under front of intake manifold. attach to VSV SW where wire are attached, Two lines run to the two SW that are on rear water bypass, seen back of intake manifold).

from what I can gather about this truck is it sat for long periods of time, most likely all winter outside.

Prolonged sitting, is damaging to fuel injectors needles. Watching fuel trims (FT) as you drive, is helpful. FT can give clues to vacuum leaks, MAF issue, fuel injectors even bad fuel pump and clogged fuel filters.

I have seen evidence of rodents in the engine bay. I wonder if this could be related.

Could be. Make sure to check for nest under intake manifold, and look for chewed wires, hoses, lines & SW.

I have access to a bore scope at work I will try and check out this filter integrity. I have an absolute bugger job of black silicon holding a hose into my intake manifold that I did not notice until after I had purchased the truck. I will have to replace the intake manifold soon as I am not comfortable going into winter like this. that would be a perfect time to work on SAI if I do need work to be done.

Is it air pipe or intake manifold that has black silicon? I see busted air pipe nipples often, number one is PCV nipple. This for sure, is area I'd correct ASAP.

As always I appreciate your insights. I will report back with my findings!

 

[Tank5]

@hortandr
Did you figure this out? I have the same trouble codes that just appeared and don’t suspect the sensors are the problem.

 

[hortandr]

Tank5 I did not figure this out. Sorry, for the late response. I wanted to get through winter up here before I dove back in.​

I am going to try any thing 2001LC has suggested in the next month or so. I suspect a rodent or water damage to wiring is the issue.​

I haven't found any one else with this issue in my searches so unfortunately we are on an island for two right now.​

Have you tried anything? Do you have a 100? I see a lot of 80 series posts on your page.​

 

[hortandr]

Ok, sharing my experience in hopes it helps someone else. A few months back the truck (2005 Sequoia 4x4) threw codes P0418 and P1613. Did some research and the common guidance was to replace the air injection driver. Easy enough to replace myself but after doing so, the codes kept intermittently coming back even after clearing them with the scan tool and disconnecting the battery.

A month or so the truck threw codes P0031 and P0051. Repair manual said the common fix is to replace the 02 sensors (both upstream and downstream). Picked up Denso replacements and swapped them out but the damn codes came back a few days later.

I could smell the truck was running rich, cold start ups were not the normal smooth process, but when it threw a P0300, P2238, and P2241 (in addition to all the others) I really became concerned.

Brought it into the shop and they dove in peeling back the wire harness leading to the ECU. Working theory was the ECU was bad or a there was an electrical short somewhere. Ultimately, they found the ground wire feeding both the secondary air injection system and air/fuel sensors was the root of the problem. Unfortunately, the ground is buried in the valley of the engine next to the starter and SAIS pump. Rather than pull the top off the engine, they were able to create a new ground and voila, CEL light and codes went away.

The truck is running great and the whole experience truly hammered home the importance of a good electrical ground!

Hey Tank5.

Found this today.
I have to replace my intake manifold soon anyways so I am planning on looking at this when I do so.
Potential ground issue would be ideal.

​

 

[jerryb]

Would be ideal IF it's at the O2 connector (2) behind the starter. More ideal is ECU or front afr's themselves. An intake removal and investigate is the last thing I'd do for an 06-07 heater circuit.
Sensors/fuses/relays/wiring. Then invasive items.