What have I done to my beloved 200?? (2 Viewers)

[Tripledave]

Yesterday, after dealing with P2447 for several months, I finally got around to installing the Hewitt Gen 2 SAIS Bypass Kit. Install went as good as expected (lost a bit of skin and blood but I've become accustomed to that). I did not install the block off plates, figured I'd save that for another day. After install, code was gone, truck drove great for several cycles. Mid-day today I thought, hey I can remote start my truck from inside the office to cool things down before running out for an errand or two. Upon my exit from said office, truck was not running. Weird... Cranked her up again and to my dismay there was a nice message on my dash telling me that something was amiss. I fired up the trusty OBD Fusion app and inspected. Found P0031 and P0051. Odd since I did not think this "mod" had anything to do with the A/F circuitry and I find it odd that BOTH O2 sensors would have the same problem at the same time. Codes will clear and return immediately, no limp mode however which means I can still drive it.

Drove home today and removed the Hewitt kit just to see if it had any effect. P0031 and P0051 still there.

Codes are as below:

P0031	Oxygen (A/F) Sensor Heater Control Circuit Low (Bank 1 Sensor 1)	- Open in A/F sensor heater circuit	Comes on	DTC stored
		- A/F sensor heater (for Sensor 1)
		- Integration relay
		- ECM

P0051	Oxygen (A/F) Sensor Heater Control Circuit Low (Bank 2 Sensor 1)	- Open in A/F sensor heater circuit	Comes on	DTC stored
		- A/F sensor heater (for Sensor 1)
		- Integration relay
		- ECM

Sure is strange that both sensors would have a problem immediately after the Hewitt install. I've reached out to Hewitt Technologies and await a response but in the meantime, I want to do some research here and see what the collective has to say. Any thoughts, troubleshooting, etc....Thanks in advance 'MUD!

 

[CharlieS]

Unplugged wires to o2 sensors? Damage to wire harness to o2 sensors? Melted wires to o2 sensors from idling?

 

[Tripledave]

Unplugged wires to o2 sensors? Damage to wire harness to o2 sensors? Melted wires to o2 sensors from idling?

In the process of checking all that now. I found this link to be useful:

Diagnostic trouble code P0031 P0032 P0051 P0052 3UR-FE | Toyota

Diagnostic trouble code P0031 P0032 P0051 P0052 3UR-FE engine control. Land Cruiser. Description. Wiring diagram. Inspection procedure.

auto-master.su

 

[grinchy]

If you want another set of sensors to compare to or try I just replaced all of mine. Just pay the ride.
These have either 120000 or 240000 miles on them, but worked fine when I took them out last week.

 

[sleepycruiser]

If you want another set of sensors to compare to or try I just replaced all of mine. Just pay the ride.
These have either 120000 or 240000 miles on them, but worked fine when I took them out last week.

Just changed them preventatively? How difficult is that on the LC200?

 

[Cruisin911]

There are 2 versions of the Hewitt bypass. One does not have a sensor input and will throw codes occasionally due to the MAF input signal. I initially had the version that resulted in the same codes you posted. Suggest you reach out to them. They had great customer service and sent me an updated version. Not an issue in years.

 

[grinchy]

Just changed them preventatively? How difficult is that on the LC200?

Yeah, my assumption is they are now 15 years old (I only have had the truck for 5, so it's not clear if they were done before), and I did it preventatively.
I used a 2 lb short hammer, 22mm wrench, a forged split socket (part # in the O2 sensor thread). The split socket makes a good target for the hammer. Took about 30 min per sensor, and I didn't remove anything for 3. For one you have to pull a heat shield (2 12mm bolts). taking down my skids would have made it easier, and if I had to do it again I might bother with it. Tough to say if it would have been 30 minutes easier or not (the time it takes to drop and rehang my skids).

I am a famously slow mechanic.

The plug on the passenger front air/fuel is a super pain to access.

 

[Tripledave]

There are 2 versions of the Hewitt bypass. One does not have a sensor input and will throw codes occasionally due to the MAF input signal. I initially had the version that resulted in the same codes you posted. Suggest you reach out to them. They had great customer service and sent me an updated version. Not an issue in years.

Interesting. I purchased the GEN 2 G22B57H1 kit which should be the latest and greatest. I did NOT install the block off plates and wonder whether this may have caused the issue. I spoke with someone at Hewitt once codes came up, they stated that they would email with some info but they did not follow through on it. Link to kit installed:

Hewitt-Tech Gen 2: Secondary Air Injection System Bypass Kit (Plug & Play)

Gen 2 (Plug & Play) SAIS Bypass Kit is compatible with most Toyota / Lexus Trucks & SUVs. It enables you to clear the Check Engine Light, Limp Mode and error codes related to both mechanical and electrical SAIS faults. P0412 P0415 P0418 P0419 P1441 P1442 P1444 P1445 P2440 P2441 P2442 P2443 P2445...

hewitt-tech.com

P0031 and P0051 cleared after removing the Hewitt kit and going through the troubleshooting procedures here:

Diagnostic trouble code P0031 P0032 P0051 P0052 3UR-FE | Toyota

Diagnostic trouble code P0031 P0032 P0051 P0052 3UR-FE engine control. Land Cruiser. Description. Wiring diagram. Inspection procedure.

auto-master.su

Monitoring both bank 1 & 2 sensors 1 & 2 show readings now that are consistent with normal operational A/F sensors. I found it quite strange that BOTH sensors would fail on low heater signals and thought it wise to fully investigate the circuits involved. I did not find anything definitive while troubleshooting (I suspect sticking A/F relay with the Integration Relay but only because I banged it on the workbench before re-installing for the last time - - real scientific right?) With all that said, I plan to re-install the bypass WITH block off plates at some point in the near future and give this a try again. If the codes come back, I will dig into Hewitt for some satisfaction on the $400 spent on their kit.

 

[Cruisin911]

So, an update to this. I ran the Hewitt bypass for years with zero issues. UNTIL I was on my way to COTR. As I am pulling in to Durango, my dash lit up like a christmas tree and threw a P0113 code with the typical 4LO, VSC, check engine, etc... lights. One twist though, the coolant temperature was showing zero (needle all the way left). When I did the valley plate repair, I put in a new SAI valve on the back of the manifold, as this was the reason for the hewitt bypass to begin with. After 15 minutes of troubleshooting, I removed the hewitt system, reconnected all the stock connections, and cleared the codes. It all came back to life and I spent a blissful 5 days in the San Juan mountains of Colorado. Long story short, I am going to see what Hewitt says about their module causing this failure.

 

[a200]

So, an update to this. I ran the Hewitt bypass for years with zero issues. UNTIL I was on my way to COTR. As I am pulling in to Durango, my dash lit up like a christmas tree and threw a P0113 code with the typical 4LO, VSC, check engine, etc... lights. One twist though, the coolant temperature was showing zero (needle all the way left). When I did the valley plate repair, I put in a new SAI valve on the back of the manifold, as this was the reason for the hewitt bypass to begin with. After 15 minutes of troubleshooting, I removed the hewitt system, reconnected all the stock connections, and cleared the codes. It all came back to life and I spent a blissful 5 days in the San Juan mountains of Colorado. Long story short, I am going to see what Hewitt says about their module causing this failure.

Any update?

 

[Cruisin911]

Yes. Apologies for not getting back to this faster. I did some troubleshooting with Hewitt and they did a warranty replacement of the module that failed. Not quite sure what the failure mechanism was but I have a brand new one sitting on the shelf in my garage. Since I replaced the AIS valves when I did the valley plate leak (very much a 'while you are in there') scenario, I have heard the pumps running and no issues at all. Should the system fail again, I will reinstall the Hewitt bypass and go from there.