Code P1604 -- Strangest Code Ever

Did a search and only found a few posts about this so I thought a thread might be more profitable...

I've discovered this bizarre P1604 code on my '14. It is defined as Startability Malfunction. However, I am not having a startability problem at all, and it runs great.

Also it is not triggering the MIL. It just lurks and shows up on the scan tool. None of the parameters seem abnormal. I've cleared the code but it likes to show up again somewhat later.

Researching this code it appears as though it appears primarily on recent model Toyotas and just about anything can cause it, or so it seems. It also appears to be one of the hardest ever to diagnose. Worse, there does not seem to be a common cause, at least from what I have read.

One thing I ran across on another forum is that killing the engine such as might occur while on a slope trying to feather the clutch can produce the code. Mine is a manual and I have done this a number of times.

I have once again cleared the code but am going to go out soon with the scan tool and intentionally kill the engine during takeoff and see what happens. Its just a curiosity at this point and under warranty so I will naturally head there next if something is not obvious.

So, has anyone diagnosed this code?

 

Wondering if you would still get the same code if your were scanning with an actual Toyota Techstream scanner .
What Generic scanner are you using? There are many false codes but if the code does come back up , do not clear it . Your scanner may have the ability to obtain the freeze frame data when the code tripped.

I posted the two most related links
http://www.e-bookspdf.org/view/aHR0...SUQ9MjA3MQ==/Rm9yZWlnbiBTZXJ2aWNlIC0gTW90b3I=

http://www.tacomaworld.com/forum/technical-chat/206861-start-ability-malfunction-2012-tacoma.html

 

Thanks much for the links GC. I previously found the TW thread but the Foreign Service article is new to me and is quite helpful.

I have the Techstream. This afternoon I went out and intentionally stalled the engine a few times. The code was not set this time so that may not be it. I need for the code to set and then study the freeze frame data line-by-line and hope to find something a bit off. There are so many parameters that will trigger it that it could take a long time.

Man what a worthless code. I would like to find it myself before going to the dealer. Surely someone has dealt with this on a Taco.

 

Info from Toyota on this code:

This DTC is stored when the engine does not start even though the STA signal is input or when the engine takes a long time to start, and when the engine speed is low or the engine stalls just after the engine starts.

Using the Techstream, the conditions present when the DTC was stored can be confirmed by referring to the freeze frame data. Freeze frame data records engine conditions when a malfunction occurs. This information can be useful when troubleshooting.

It is necessary to check if the vehicle ran out of fuel before performing troubleshooting, as this DTC is also stored when there is engine starting trouble due to running out of fuel.

HINT
* In contrast to normal malfunction diagnosis for components, circuits and systems, DTC P1604 is used to determine the malfunctioning area from the problem symptoms and freeze frame data when the user mentions problems such as starting difficulty.
As these DTCs can be stored as a result of certain user actions, even if these DTCs are output, if the customer makes no mention of problems, clear these DTCs without performing any troubleshooting and return the vehicle to the customer.
* If any other DTCs are output, perform troubleshooting for those DTCs first.
* When the Data List item "Immobiliser Fuel Cut" is ON, the engine cannot be started.
* Read freeze frame data using the Techstream. Freeze frame data records engine conditions when a malfunction occurs. This information can be useful when troubleshooting.
* When confirming the freeze frame data, be sure to check all 5 sets of freeze frame data See: Computers and Control Systems > Scan Tool Testing and Procedures > Freeze Frame Data.
* When confirming freeze frame data, if there are multiple items related to the cause of the malfunction, perform troubleshooting for all related items.
* Try to start the vehicle under the conditions recorded in the freeze frame data which were present when the malfunction occurred. Confirm the data at this time and compare it with the freeze frame data.
* If the malfunction does not reoccur, carefully check the vehicle conditions from when the malfunction occurred using freeze frame data.
* When performing inspections, jiggle the relevant wire harnesses and connectors in an attempt to reproduce malfunctions that do not always occur.
* If the same inspection or replacement procedure appears 2 times when performing an inspection procedure, it is not necessary to repeat the procedure the second time.




The general information shows that this is a Class C code, which means it will NOT turn on the CEL light. So this explains why the code sets, but you get no light.

 

ok, I went out and tried a bunch of things and can get this code to trigger consistently on my 6-speed. If I stall the engine twice in a row during an easy take off, when there is not quite enough throttle being used, the code will appear.

In trying to diagnose this a dialog box always appears on screen that says do not diagnose. Huh? Also a CEL has yet to appear. So it appears to be storing the code but not trigger a check engine light under the conditions described and does want you to do anything about it.

Again, it looks like there a bunches of things that can produce this code more than what I found but only certain things are considered serious enough to trigger a CEL

 

Hey Toyota tech chiming in here. This code is nothing.. It is a code put in place to appease governments. This is the explanation I have received from higher ups.

 

BCTSR5, thanks for chiming in. Wow, nothing surprises me anymore.

 

I retrieved that code in my '14, 2.7, manual tran 4x4. I too am a tech at an indie garage. My truck intermittently upon cold start will long crank then stall. second try will crank start and have a low idle speed... then all normal. 20k miles. the freeze frame data was all out of whack too engine load way high, rpm out of range etc... cleaned throttle body cleared code wait for it to do it again. ??

 

Thanks 4X4Rob. The strangest thing about this is I have Tonka's techstream and when I try to diagnose the code it always pops up a window on the screen saying "Do not diagnose." WTH is up with that? It also has never set the CEL. I just clear it but that starts the whole drive cycle stuff all over again. I wonder what is so sensitive about these late model trucks? As I stated, mine starts perfect, idles perfect, and runs perfect. And nothing obvious appearing with the freeze frame stuff.

I'm willing to bet there are a bunch of folks driving around out there with this code lurking and just don't know it because no warning light ever comes on.

 

The code is a government regulatory code. If your truck is stalling after running then u should have more than p1604. The code will set if the key is not held fully while starting until the engine actually fires up. In the code it says do not diagnose, do what it says... U won't get anywhere. Just leave the code there it wont mess anything up

 

^^ This is great! We are making progress now.

 

IMHO the code is only relevant to push button start capable engine computers

my Yaris is like this. I have a key, but it is full push button start capable.

I can just twist the key fast and let go, and the thing will start on it's own
and keep cranking until it starts without me holding the key.

Once when I had done a series of
very short trips (1/2 mile) and on a really damp cold morning, it cranked
too long and stopped. tried again it worked. no MIL but this code was on
deck, and apparently cleared itself after 'the driving pattern' was performed.

 

Mine came after it was in at a tire shop.. if you're right then it probably was generated because they didn't allow the engine to turn over when turning the key.

 

I have this code on my mistress' 2011 Highlander. So, basically disregard until the check engine lite comes on for good?

 

are you a pro mechanic? or just an enthusiast? I ask bc I am thinking of getting the techstream. What subscription do you have? I consider myself an advanced DIY shade tree mechanic. Thanks for any info on this.

 

no is not! I am here bc my 2011 Highlander has this mf'ng code and there is very little info on it while searching under Highlander. Google search got me here. The 2011 Highlander is a key start.

 

A pro? hardly. Just someone curious about funny codes and other strange happenings.
I got the TS clone cable that was about $29 at the time and came with some software, but being afraid of bugs, found some dependable software for free online. Dug out an old computer and have it dedicated now as a diagnostic tool for the Taco. Best thing ever and it will do almost everything the dealer can, except reflashing.

 

your highlander engine and computer is button start capable, it just has a key instead.

same as my 2010 yaris, in USA it has a key but everywhere else button start, it is ready... just install the actual button
from some other country where yaris was sold with button start

 

I have a similar issue on my 2012 tom

I having a similar issue with my 2012 Tocoma Automatic. I use a FixD app. it keeps bring up code 1604 and 1605. However, I have no starting issues, with the truck. I am however noticing that its running a little rough, something I'm going to look into further. But as far as starting. No issues.
I don't think it's the app giving me a false read.

Have looked through the threads, doesn't seem to be anything definative regarding these codes.

 

The codes seems to be set when the engine takes longer than a set time period. I’ve not seen any specific time listed.

Can you clear the code, and if so does it return?