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Hi. I'm Dave,
Thank you for choosing justanswers.com for help with your situation.
It looks like you have several issues here. I will attempt to cover all of them.
We will start with DTC P2422 and DTC P2119P. The "P" at the end of P2119P is your scan tool indicating that this is a "pending" code that has not actually set yet.
There is no information in the service manual for this vehicle on how to service these Diagnostic Test Codes. However, there IS a Technical Service Bulletin (TSB) Published by the manufacturer that lists these codes as "FASE CODES" for this model. It requires reprogramming of the Engine Control Module to correct the problem.
Click HERE to download a copy of the TSB.
When DTC P0128 is set, a skewed Engine Coolant Temperature (ECT) sensor or a stuck-open thermostat is indicated. Basically, the computer looks at the ECT at engine start-up. After several minutes of engine running, it looks at the sensor again. It expects a minimum rise in temperature to occur during this time. If the computer does not see the expected rise in temperature this code is set.
DTC P0121 basically means the Throttle Position Sensor (TPS) signal indicates a value other than expected.
This is most likely your main problem when it comes to the way that the vehicle is running. The computer needs the TPS input to control the idle speed, the fuel to the injectors and the advance for the ignition timing. When this signal is not correct, the engine cannot control these things the way it should and it can cause the driveability symptoms you are describing.
The TPS is an integral part of the throttle body assembly on this model. If the sensor itself needs to be replaced, the entire throttle body must be replaced. If the throttle body is replaced, the computer once again has to be reprogrammed to set the "idle learning" for the new throttle body.
I know this is probably the LAST thing you wanted to hear, but I highly recommend taking the vehicle to the dealer for these problems so they can all be taken care of at the same time. You will probably have to do this anyway to get the computer reprogrammed (DTC P2422 and DTC P2119P and possible throttle body replacement) unless you have the pass-through equipment necessary to reprogram it yourself. (I am assuming that if you had this type of equipment, you would also have access to the service information for the vehicle, and would not be asking for my help on the codes you are getting)
Trust me, I HATE having to tell a customer to "Take it to the dealer" as much as most of my customers hate hearing me tell them that...I am an aftermarket technician, and that is the last thing I want to tell any customer to do. There are also some aftermarket shops that have the equipment and service information necessary to do this. But in any case, you are not likely going to be able to do this yourself at home.
About the only thing listed here that would be "user-serviceable" would be the thermostat and/or temperature sensor (DTC P0128). I would try a thermostat first - this is the usual cause. However, this will not fix the issues with the engine stalling and you probably will not see any "noticeable" change in performance as a result of fixing this.
Sorry, I wish I had a more simple solution for you. However, it would be a great disservice to you and very unprofessional of me if I was not up-front and honest with you about the issues you are facing here.
Let me know if there is anything else I can do for you concerning these things.
Thanks Dave for your reply. Is the throttle body absolutely need to be replaced? I went to some forums and they are saying in most cases a throttle body only need to be cleaned. Unless it has a crack then a replacement is necessary. And also it seems like not just one person has been have issue with the computer in Suzuki Verona. Could this be the case of a fail computer? If I'm getting consistent error code, does this means the computer is functioning fine? As you might know already Suzuki motor vehicle had left USA already and their dealership location is very limited. It is hard for me to transfer my car to one of their location so I'm trying to see if any shop will be able to solve this. I'm really close to a sears.
No, it is not "absolute" that the throttle body needs to be replaced. However, we are talking about an ELECTRICAL fault here. The computer is setting the code because it is not seeing the correct voltage at idle...I fail to see how "cleaning" a throttle body will correct an electrical fault. There are also other things (besides the TPS Sensor itself) that can cause incorrect voltage readings like loose or corroded connector pins, wiring harnesses that have rubbed through on something and shorted the wires out, etc. This is why the problem should be properly diagnosed - to avoid misdiagnosis and possibly replacing parts that do not need to be replaced.
Yes, there could possibly be a computer failure - Again, that is what diagnosis is for...to determine the ACTUAL CAUSE of the fault codes you are getting. It should also be noted that computer module failures are VERY RARE. However, you would not guess this by the number of replaced computer modules you will count in the online DIY forums. Way too many amateurs will blame anything they cannot explain on "the computer" and replace the module only to find out that they still have the same problem. Just read any of the online DIY forums to verify that this statement is true...
On the other hand, when the vehicle manufacturer publishes a Technical Service Bulletin that states that the codes you are getting are "FALSE CODES" and that the fix for the problem is computer reprogramming, they are usually correct.
Dave, Thank you for taking your time for the detailed reply. But unfortunately non of your recommended repair matches dealer's diagnosis.
For the TSB of reprogramming the computer, dealer says it does not apply in this case. Their check indicate code P2422 came from bad engine harness, which is the reason for all this codes but P0128. I personally printed and red the TSB you provided and non of the above codes pop up on that bulletin.
Throttle body, according to them, has no issue at all. Tech says by adjusting the engine harness, vehicle can start with no problem. From research and also from the tech we found out the original wiring harness for verona had design flaws that would caused the wires to corrode and form intermittent connections. And Suzuki dealers are being instructed to replace the wiring harness, at customer cost, when the vehicle arrive with any issue that might because of the false harness.
Dave, I really appreciate your long reply, but it also really don't help me if your answer is simply just "go see the dealer." I came to you guys seeking professional help on issues with this vehicle and I do plan to see constructive advises according to this vehicle.
I would like to address some of the statements you have made here.
"But unfortunately non of your recommended repair matches dealer's diagnosis."
I never actually recommended any "repairs". I only tried to explain to you what some of the possible causes are of the codes that you are getting. I explained what the computer is looking for and what conditions causes the codes to set.
This is PERFECTLY in line with the dealer's diagnosis. For example, I stated "DTC P0121 basically means the Throttle Position Sensor (TPS) signal indicates a value other than expected." The dealer is telling you that there is a wiring harness fault....this is one and the same. The wiring harness problem is WHAT CAUSED the computer to be getting a reading other than what is expected.
When you asked for clarification if I was telling you that the throttle body "absolutely" needs to be replaced. I did not tell you to replace the throttle body. I clearly stated "No, it is not "absolute" that the throttle body needs to be replaced. However, we are talking about an ELECTRICAL fault here. The computer is setting the code because it is not seeing the correct voltage at idle..." Keep in mind that I was only responding to what you asked, as well as your statement that you read somewhere that "cleaning the throttle body" could fix the problem. I still maintain that cleaning the throttle body will NOT fix an electrical fault. Again, this is perfectly in line with what the dealer has told you. The only difference is that I was telling you WHY the code was setting, the dealer has now told you WHAT caused it.
"For the TSB of reprogramming the computer, dealer says it does not apply in this case".
That is precisely the reason I recommended that you take it to the dealer for proper diagnosis (maybe not such bad professional advice after all???). There is no way to know if the articles in the TSB apply until "hands on" diagnostics is performed, as well as accessing the computer data to verify if the latest software update has been installed in the onboard computer. I have no way of knowing this working with you online.
The TSB itself even states that the vehicle should be checked for other failures before the reprogramming is done: "Using the appropriate service manual, verify the DTC using the troubleshooting chart to be sure the code has not been set due to an actual fault."
I clearly stated that the vehicle needed to be DIAGNOSED to find the CAUSE. "Again, that is what diagnosis is for...to determine the ACTUAL CAUSE of the fault codes you are getting." This is not something that can be done over the internet. All that can be done by this venue is to give you some of the possible causes, and try to give you some solid advice as to how to go about handling the situation. Sorry, I cannot diagnose and repair vehicles over the internet. However, the information I provided was accurate and perfectly in line with what turned out to be the diagnosis provided by the dealer in order to come up with the fix. The information I provided about the codes involved were straight from the published service information provided by the vehicle manufacturer - the very same information used by the dealership techs that diagnosed your vehicle.
" I personally printed and red the TSB you provided and non of the above codes pop up on that bulletin."
All I can say to that is I would recommend reading the bulletin again. It CLEARLY lists the two codes I indicated (DTC P2422 and DTC P2119) for the Model Year (MY) 05 vehicles. (See clip from the TSB below)
"I came to you guys seeking professional help on issues with this vehicle..."
Sorry you seem to be disappointed. When there are computers and fault codes involved, there is only so much that can be done over the internet. There is simply no way to physically inspect wiring harnesses and connectors, or check for corrosion with a keyboard and a mouse. This is something that can only be done in person. In the meantime, I can only offer professional "advice" and/or "instruction". I cannot diagnose your vehicle since I have no access to the vehicle. This means that any diagnosis MUST come from your end. This is about as good as it can get for this type of situation, unless you have the equipment and skills necessary for me to give you instruction on how to actually diagnose the vehicle yourself. Again, sorry, but there are certain things I simply have absolutely no control over from here.
I can only provide accurate and truthful information based on the facts that I have to work with. If you take a second look, you will see that I have done that.
Let me know if there is anything else I can do for you.
Just thought I would also mention that if you look back up on the page to my second answer, you will see that I stated pretty much EXACTLY what the dealer has told you.
"There are also other things (besides the TPS Sensor itself) that can cause incorrect voltage readings like loose or corroded connector pins, wiring harnesses that have rubbed through on something and shorted the wires out, etc. This is why the problem should be properly diagnosed - to avoid misdiagnosis and possibly replacing parts that do not need to be replaced."
Just thought I should mention that, given the fact that you seem to think that nothing I told you agrees with what you are being told by the dealership tech.