Help! Troubleshooting Yanmar T175 Engine Codes and Derate

[Cory151]

Greetings,

Was on a worksite (my first big job of clearing and grading 1 acre for a home build), when all of the sudden my compact track loader started to sputter stall intermittently now it seems to be permanently derating. Here are the codes that are coming up on the to 2018 Yanmar T175 with the 4TNV98C (Same as the Gehl RT175). I don't have a troubleshooting manual but I found one online and next to the fault I wrote in the fault description from the manual:

157-16 "PLV open"
523470 "Rail Pressure Fault (pressure to high)
523489 "Rail Pressure Fault (time of opening error)

I figure something must causing the pressure relief valve to pop off and perhaps it was the SCV? I was able to do a search here and find someone with an excavator having a similar issue but they had 3TNV and mine is the 4TNV. Wondering if perhaps the SCV (suction control valve or regulator) valves are interchangeable? Also if I change whatever part is the root cause will the code clear on its own?

Thank you to all for any wisdom.

 

[Cory151]

Here is a link to a thread I found with a similar issue, but I do not believe I received any bad fuel as the Superduty that pulls it gets topped off at the same time and like most modern diesels is extremely sensitive to poor fuel quality. https://www.heavyequipmentforums.com/threads/3tnv88c-tier-4-rail-pressure-issues.79494/

Attached is a pic of the machine in question.

 

[Cory151]

Here is a screenshot of there SCV and pump assembly and I confirmed that the part # 129A00-51100 is the same for both the Turbo and non turbo variant, 4TNV98CT and the 4TNV98C. Im considering finding one online cheaper and throwing it in the pump and see what happens, but I know that throwing parts at things is not good troubleshooting.

 

[John V]

I don't have much help to offer right now, but here is the yanmar engine service manual which includes your model: https://drive.google.com/file/d/13dVzMNFzERPw7p76OZXED9URvJY8n-c0/view?usp=sharing

 

[John V]

According to the yanmar parts website, the SCV valve part number is the same between the 4tnv and my 3tnv. Here is the link where I purchased mine from: https://spareto.com/products/bosch-control-valve-fuel-quantity-common-rail-system/1-462-c00-983

 

[Cory151]

According to the yanmar parts website, the SCV valve part number is the same between the 4tnv and my 3tnv. Here is the link where I purchased mine from: https://spareto.com/products/bosch-control-valve-fuel-quantity-common-rail-system/1-462-c00-983

Thanks for the reply, I purchased mine from here but am still waiting for delivery: https://partsbos.shop/fuel-control-...e-33100-2f100-129a00-51100-4047024437586.html

Question for you John.... I already removed the old one and it looks fine (like yours), do you know if there is anything I need to do to reset the codes on this 2015 Yanmar? Will installing the good SCV clear the codes?

 

[Cory151]

Received the SCV from the link above and it is, in fact a Bosch part. Threw it in and the code didn't clear called Yanmar America and they said the ECU keeps a count of common rail pressure relief opening events and I would need a dealer computer to reset that count to zero.

 

[John V]

Yep that sounds right, I believe my dealer cleared something for me.

 

[Cory151]

Followed up with Yanmar today and it's looking like I replaced the wrong part. As posted above I replaced suction control valve or SCV which is basically just fuel pressure regulator and took it to the dealer to have the ECU rail overpressure count reset.

They said that the computer is showing around five hours or pressure relief via the (PRV/PLV), so they think it maybe the valve itself that failed. Boy am I glad I spent $175 on that Bosch fuel regulator instead of the $780 Yanmar wanted.