Discussion: how to make 4wd more reliable in the 5th gen

[wfo9]

Thought this might be worth a discussion.

I know some people will get bent out of shape on this subject because it is not popular to talk about the weaknesses of these trucks here... but hear me out for a second and try to be open minded.

A recent experience of a friend with a 5th gen made me realize how unreliable these trucks are when it comes to the part time 4wd system. Especially as they age and start getting a decent amount of miles on them.

The system itself is not unreliable, it's based on a solid foundation of reliable mechanical components... However, Toyota has made any malfunction that throws a MIL/CEL on the entire truck.. disable the 4wd system. This means that lots of fragile sensors need to all be happy for the system to work, even if the sensor has absolutely nothing to do with 4wd or the normal operation of the truck.

Here is the scenario... you are out the desert camping and exploring for 2 weeks thousands of miles from home. You get a simple CEL/MIL set. This could be anything from a loose gas cap, to a catalytic converter efficiency or EVAP code, to an actual engine misfire. Well guess what... no ability to engage 4wd and your trip is a bust unless you can resolve the issue. Even when the truck is running perfect....

Why? Well even though you tried to think this scenario through and purchased a trail edition or one of the older sr5s with a manual transfer case, Toyota decided that anytime a MIL is set.. Disable the 4wd ECU and don't allow the ADD to engage the passenger side axle. If you add a front locker... you can still get 3wd... but that configuration puts major stress on the single CV and would not be ideal.. There is no logic behind the 4wd being disabled besides the fact that they just wanted to treat any malfunction the same and force you into a dealer vs only disabling 4wd for relevant problems. My guess is that it will stay in 4wd if you are already engaged... So any reasoning that 4wd can't operate without all the sensors happy is not valid.

The chances of something like this happening are pretty high as the vehicle ages... and many of the emissions codes are just part of owning an older vehicle. I realize 5th gens are only about 7-8 years old now and this is currently not that common, but in 5 years from now these types of issues will be fairly common and many people won't care that their catalytic converter needs to be replaced while out in the middle of nowhere.... Yet they won't be able to use 4wd unless they come up with a solution.

Another unrelated yet common problem is the tcase switches that fail. These will also disable your ability to use 4wd, but are really only ECU related.

What I would like to do is discuss how the ADD could be wired up to engage via an override switch. That is the only thing mechanically stopping 4wd from working on a manual T-Case truck. Just like you can hard wire the rear locker it should be possible to hard wire the ADD. I have not even looked at the wiring diagram yet... but it is on my backlog of things to do.

The next question would be... If the ECU does not know it is in 4wd... and you got the ADD to hotwire or manually engage.. How would TRAC and all the other fly by wire electronics limit the trucks ability to go off-road. Things like ATRAC, crawl, and all the other electronic gadgets would not work, but would the basic traction control get in the way of actually offroading the truck. 4LO normally turns off most things, so the truck actually works with wheel spin. Regular 2H behavior is pretty odd when the wheels start to slip unless you can disable the traction control, but I'm hoping all that gets disabled with a MIL or you can still manually turn it off.

This is not a priority for me at the moment, but something I want to research as time permits. I feel it is an inevitable situation as the truck ages and it would be nice to have a mitigation strategy in place. I use this truck to do long trips offroad.. and if the truck fails... the trip is a bust. I understand mechanical things can and will happen... I can accept that, but that is the reason I have the 4r vs a Jeep. The BS electronics are much more frustrating if they stop you and I feel Toyota has made a mistake here.

 

[sinks88]

Im interested in this discussion.

 

[SATSTRAIL]

Bring a code reader to clear any code that may set while wheeling. This will work for minor issues that require the OBD system to test for and see an actual failure, like catalyst and evap issues and anything intermittent. A constant misfire would be a different story..

 

[wfo9]

Bring a code reader to clear any code that may set while wheeling. This will work for minor issues that require the OBD system to test for and see an actual failure, like catalyst and evap issues and anything intermittent. A constant misfire would be a different story..

That may not work... but is a good suggestion to try for intermittent stuff. Many of the test run on each startup...

 

[philsey]

But .... I'll be OK going to Costco, and the liquor store, and the cleaners ... right?

ETA: Oh, and the SSA office too.

 

[1engineer]

Your thread title is nothing but click bait. The components are reliable. Reading your post, you want to find a way to bypass Toyota programming logic to keep certain mechanical systems operational.
This has nothing to do with reliability and everything to do with the inability to troubleshoot and repair the electronics necessary to keep specific subsystems functioning.
In my world, you are looking for a way to "bridge out" multiple fail safes in order to keep your machine operating. Right? Here is a partial quote from your post:

"The system itself is not unreliable, it's based on a solid foundation of reliable mechanical components... However, Toyota has made any malfunction that throws a MIL/CEL on the entire truck.. disable the 4wd system. This means that lots of fragile sensors need to all be happy for the system to work, even if the sensor has absolutely nothing to do with 4wd or the normal operation of the truck."

Basically what you are saying is, and truthfully so, is we (collectively) do not have the ability to fix or repair the electronic components necessary to provide proper operation of this vehicle. I would agree.

I'll be happy to change your title.

 

[(none)]

Gotta admit. I was unaware a CEL actually disabled the 4wd system. When I installed my TRD intake I forgot to plug in the air injection or EGR and it started with a CEL and the terrain select light, but I assumed it'd still go in 4wd. That's crazy.

I like the idea of just removing the electric motor from the ADD and making it fully manual. It could be actuated from a cable running either under the hood or to a wheel well. This is similar to what JK rubicon owners usually do when the motor for the electronically disconnecting front sway bar fails. I guess that depends, though, on what switches it uses to determine the "locked" and "unlocked" positions of the ADD.

If you already have it in 4wd, then a CEL illuminates, does it automatically unlock itself?

 

[007Tacoma]

Bring a code reader to clear any code that may set while wheeling. This will work for minor issues that require the OBD system to test for and see an actual failure, like catalyst and evap issues and anything intermittent. A constant misfire would be a different story..

So, this is actually why I bought a ScanGauge II for my 2003 4Runner. The day after I bought it I got a CEL/MIL for the O2 sensors. Yeah. The previous owner was reseting the light before I test drove it. The Catalytic Converters had failed, and it was going to be too expensive to replace them. This has been discussed ad-nauseum on the 4th Gen forum.

Enter the ScanGuage II - I spent the next 8 months resetting the CEL/MIL whenever it came up. I finally ponied up for an O2 Sensor Simulator from URD. That took care of the CEL/MIL for good, but my emissions were still toxic.
ainkiller:

Learning from that experience, I have the ScanGauge II still and a Carista.

Your thread title is nothing but click bait. The components are reliable. Reading your post, you want to find a way to bypass Toyota programming logic to keep certain mechanical systems operational.
This has nothing to do with reliability and everything to do with the inability to troubleshoot and repair the electronics necessary to keep specific subsystems functioning.
In my world, you are looking for a way to "bridge out" multiple fail safes in order to keep your machine operating. Right? Here is a partial quote from your post:

"The system itself is not unreliable, it's based on a solid foundation of reliable mechanical components... However, Toyota has made any malfunction that throws a MIL/CEL on the entire truck.. disable the 4wd system. This means that lots of fragile sensors need to all be happy for the system to work, even if the sensor has absolutely nothing to do with 4wd or the normal operation of the truck."

Basically what you are saying is, and truthfully so, is we (collectively) do not have the ability to fix or repair the electronic components necessary to provide proper operation of this vehicle. I would agree.

I'll be happy to change your title.

Agreed/disagreed. I think it accurately got his point across for the sake of understanding that there might be future problems.

...maybe a bit click-baity, but it got me to look.op2:

 

[HTXpro]

I read the title and thought to myself 'I wasn't aware the 4WD system was fragile.' Reading your post makes sense though. I hate the electronics in this thing. I forgot to tighten the gas cap for the first time ever in 19 years of driving, and my dash was lit up like a Christmas tree. I don't understand why a gas cap would cause ABS, TC, and several other systems to malfunction.

 

[HerT4R]

Your thread title is nothing but click bait. ...

I'll be happy to change your title.

Alternative title options:

"Codes that will make 4WD unusable"

"How to bypass codes that make 4WD unusable"

"Electrical bypass to codes that make 4WD inaccessible"

"Sensor/codes suck" :brushteeth:

 

[CruzadoBlanco]

Thought this might be worth a discussion.

I know some people will get bent out of shape on this subject because it is not popular to talk about the weaknesses of these trucks here... but hear me out for a second and try to be open minded.

A recent experience of a friend with a 5th gen made me realize how unreliable these trucks are when it comes to the part time 4wd system. Especially as they age and start getting a decent amount of miles on them.

The system itself is not unreliable, it's based on a solid foundation of reliable mechanical components... However, Toyota has made any malfunction that throws a MIL/CEL on the entire truck.. disable the 4wd system. This means that lots of fragile sensors need to all be happy for the system to work, even if the sensor has absolutely nothing to do with 4wd or the normal operation of the truck.

Here is the scenario... you are out the desert camping and exploring for 2 weeks thousands of miles from home. You get a simple CEL/MIL set. This could be anything from a loose gas cap, to a catalytic converter efficiency or EVAP code, to an actual engine misfire. Well guess what... no ability to engage 4wd and your trip is a bust unless you can resolve the issue. Even when the truck is running perfect....

Why? Well even though you tried to think this scenario through and purchased a trail edition or one of the older sr5s with a manual transfer case, Toyota decided that anytime a MIL is set.. Disable the 4wd ECU and don't allow the ADD to engage the passenger side axle. If you add a front locker... you can still get 3wd... but that configuration puts major stress on the single CV and would not be ideal.. There is no logic behind the 4wd being disabled besides the fact that they just wanted to treat any malfunction the same and force you into a dealer vs only disabling 4wd for relevant problems. My guess is that it will stay in 4wd if you are already engaged... So any reasoning that 4wd can't operate without all the sensors happy is not valid.

The chances of something like this happening are pretty high as the vehicle ages... and many of the emissions codes are just part of owning an older vehicle. I realize 5th gens are only about 7-8 years old now and this is currently not that common, but in 5 years from now these types of issues will be fairly common and many people won't care that their catalytic converter needs to be replaced while out in the middle of nowhere.... Yet they won't be able to use 4wd unless they come up with a solution.

Another unrelated yet common problem is the tcase switches that fail. These will also disable your ability to use 4wd, but are really only ECU related.

What I would like to do is discuss how the ADD could be wired up to engage via an override switch. That is the only thing mechanically stopping 4wd from working on a manual T-Case truck. Just like you can hard wire the rear locker it should be possible to hard wire the ADD. I have not even looked at the wiring diagram yet... but it is on my backlog of things to do.

The next question would be... If the ECU does not know it is in 4wd... and you got the ADD to hotwire or manually engage.. How would TRAC and all the other fly by wire electronics limit the trucks ability to go off-road. Things like ATRAC, crawl, and all the other electronic gadgets would not work, but would the basic traction control get in the way of actually offroading the truck. 4LO normally turns off most things, so the truck actually works with wheel spin. Regular 2H behavior is pretty odd when the wheels start to slip unless you can disable the traction control, but I'm hoping all that gets disabled with a MIL or you can still manually turn it off.

This is not a priority for me at the moment, but something I want to research as time permits. I feel it is an inevitable situation as the truck ages and it would be nice to have a mitigation strategy in place. I use this truck to do long trips offroad.. and if the truck fails... the trip is a bust. I understand mechanical things can and will happen... I can accept that, but that is the reason I have the 4r vs a Jeep. The BS electronics are much more frustrating if they stop you and I feel Toyota has made a mistake here.

if you want to be able to bypass the 4wd ECUs ability to not engage the ADD look over at the rocksolidtoys forum. there is a write up on how to wire the ADD up to be switch controlled and not go through the ECU. now it will only work with the manual Tcase. if youre going that far you might as well just go all out on it and finish pinning it out and fully get rid of the 4wd ECU, youd still have the lights in the dash work, but youd also have to put the factory locker on a new switch as well and youd totally lose atrac, but who uses that anyway.

or you could just get a v8 4th gen and not have the ADD or a lot of other sensors to worry about.

 

[JeremyB]

So, this is actually why I bought a ScanGauge II for my 2003 4Runner. The day after I bought it I got a CEL/MIL for the O2 sensors. Yeah. The previous owner was reseting the light before I test drove it. The Catalytic Converters had failed, and it was going to be too expensive to replace them. This has been discussed ad-nauseum on the 4th Gen forum.

There are several PIDs you can look at to see if the seller is resetting before you test drive. If it's low or zero (like it was in your case), you can confront the buyer about what's up and/or look into it further.

https://en.wikipedia.org/wiki/OBD-II_PIDs#Mode_01
Mode 1, 30: Warm-ups since codes cleared
Mode 1, 31: Distance traveled since codes cleared
Mode 1, 4E: Time since trouble codes cleared

 

[wfo9]

Your thread title is nothing but click bait.
I'll be happy to change your title.

I'm shocked that we have to have politically correct titles. It seemed accurate to me.

The system has flaws just like everything else.. Toyota makes choices that often impact the end user in unexpected ways... It's life... bury your head in the sand or find solutions.

I would hope people can read past a title. It's hard to get an entire point across in 5 words.

 

[ToolUser1]

I disagree completely. Designing failure modes that simply cause _everything_ to stop working, without regard to safety or system impacts, is lazy engineering at best. Where I work it would get you fired pretty quickly.

The failure of an 02 sensor has no impact on either operator safety or system integrity, so having it trigger a cascade of unrelated failures is simply not acceptable. Think of it in terms of an aircraft or a spacecraft and you can quickly see how poorly this design philosophy translates to the real world.

If it's true, it's such bad engineering it would be grounds for moving away from Toyota. I'll need to perform some tests to confirm.

Your thread title is nothing but click bait. The components are reliable. Reading your post, you want to find a way to bypass Toyota programming logic to keep certain mechanical systems operational.
This has nothing to do with reliability and everything to do with the inability to troubleshoot and repair the electronics necessary to keep specific subsystems functioning.
In my world, you are looking for a way to "bridge out" multiple fail safes in order to keep your machine operating. Right? Here is a partial quote from your post:

"The system itself is not unreliable, it's based on a solid foundation of reliable mechanical components... However, Toyota has made any malfunction that throws a MIL/CEL on the entire truck.. disable the 4wd system. This means that lots of fragile sensors need to all be happy for the system to work, even if the sensor has absolutely nothing to do with 4wd or the normal operation of the truck."

Basically what you are saying is, and truthfully so, is we (collectively) do not have the ability to fix or repair the electronic components necessary to provide proper operation of this vehicle. I would agree.

I'll be happy to change your title.

 

[1engineer]

I'm shocked that we have to have politically correct titles. It seemed accurate to me.

The system has flaws just like everything else.. Toyota makes choices that often impact the end user in unexpected ways... It's life... bury your head in the sand or find solutions.

I would hope people can read past a title. It's hard to get an entire point across in 5 words.

There is a big difference between "politically correct" and realistic lol. You want to figure out a way to bridge out all electronic safeties so you can still use the mechanical functions. That's realistic. It has nothing to do with reliability and everything to do with spoofing or bypassing Toyota CEL/MIL logic.

 

[wfo9]

if you want to be able to bypass the 4wd ECUs ability to not engage the ADD look over at the rocksolidtoys forum. there is a write up on how to wire the ADD up to be switch controlled and not go through the ECU. now it will only work with the manual Tcase. if youre going that far you might as well just go all out on it and finish pinning it out and fully get rid of the 4wd ECU, youd still have the lights in the dash work, but youd also have to put the factory locker on a new switch as well and youd totally lose atrac, but who uses that anyway.

or you could just get a v8 4th gen and not have the ADD or a lot of other sensors to worry about.

Good info. I found some info over there that I need to digest and see if I can come up with a harness. I don't want to bypass the entire 4wd ECU. I just want to find a way to engage the ADD in a pinch. Even manual engagement would not be a terrible option. Taking the skids off... would take some time, but you could just leave it on until back to 100% paved roads.

 

[wfo9]

I disagree completely. Designing failure modes that simply cause _everything_ to stop working, without regard to safety or system impacts, is lazy engineering at best. Where I work it would get you fired pretty quickly.

The failure of an 02 sensor has no impact on either operator safety or system integrity, so having it trigger a cascade of unrelated failures is simply not acceptable. Think of it in terms of an aircraft or a spacecraft and you can quickly see how poorly this design philosophy translates to the real world.

If it's true, it's such bad engineering it would be grounds for moving away from Toyota. I'll need to perform some tests to confirm.

I can confirm... It's true LOL. It makes no sense to me either, but I'm not going to give up on Toyota over it. It is give and take... Toyota has always been this way when it comes to electronics. It is not their area of strength. They have things that make up for it though. Nothing is perfect.

 

[1engineer]

I disagree completely. Designing failure modes that simply cause _everything_ to stop working, without regard to safety or system impacts, is lazy engineering at best. Where I work it would get you fired pretty quickly.

The failure of an 02 sensor has no impact on either operator safety or system integrity, so having it trigger a cascade of unrelated failures is simply not acceptable. Think of it in terms of an aircraft or a spacecraft and you can quickly see how poorly this design philosophy translates to the real world.

If it's true, it's such bad engineering it would be grounds for moving away from Toyota. I'll need to perform some tests to confirm.

...which goes to show how little you know about complete systems. When certain components fail on say, an aircraft, there is redundancy built in. In addition to redundancy, there are other systems that shut down to keep from messing up other components. Do you want to pay $100K for a properly designed bulletproof 4Runner? Nobody else does either, which is why they are not built like aircraft.

 

[Kimokona]

Your thread title is nothing but click bait. The components are reliable. Reading your post, you want to find a way to bypass Toyota programming logic to keep certain mechanical systems operational.
This has nothing to do with reliability and everything to do with the inability to troubleshoot and repair the electronics necessary to keep specific subsystems functioning.
In my world, you are looking for a way to "bridge out" multiple fail safes in order to keep your machine operating. Right? Here is a partial quote from your post:

"The system itself is not unreliable, it's based on a solid foundation of reliable mechanical components... However, Toyota has made any malfunction that throws a MIL/CEL on the entire truck.. disable the 4wd system. This means that lots of fragile sensors need to all be happy for the system to work, even if the sensor has absolutely nothing to do with 4wd or the normal operation of the truck."

Basically what you are saying is, and truthfully so, is we (collectively) do not have the ability to fix or repair the electronic components necessary to provide proper operation of this vehicle. I would agree.

I'll be happy to change your title.

Click bait, those are pretty strong words !

While I really like my new 2016, I would have preferred manual hubs and transfer case shifting, lord forbid the new Bluetooth adapter takes out my ability to engage 4WD : ) I'm certainly intrigued.

I'm an operator for a large central plant facility and can use my smart phone to operate the plant & facilities remotely, if that fails, use the LAN computer, if that fails, activate individual controllers for each component to restore operations.

If that fails, go into the field and individually power up each device, turn each valve in proper sequence, to restore operations.

Recently we had a contractor destroy a section of fiber to our largest facility, 1700' had to be replaced. It took 3 weeks to complete repairs, we operated by hand until then and never missed beat.

Stuff happens, I love a good backup plan !

 

[1engineer]

[MENTION=106176]wfo9[/MENTION] this is a good thread and hopefully people will stay on topic (instead of useless complaining) to garner good and innovative ideas on the control side.