The turbo control valve (TCV) on my T5-R

Cincyken · Post by **Cincyken** » 17 May 2012, 16:25

how does it work?
It is a solinoid, that on an electrical signal alters the air flow thru it.
It has three hoses:
Red is to the turbo compressor (this should be a positive pressure off the turbo casing)
Blue is an atmospheric connection (not sure if it pulls in air or discharges air)
Yellow is the turbo waste gate.
This is what i think goes on.
At some predetemined value the computer takes the pressure from the red line and sends it to the yellow line thru the TCV to the wastegate actuator. Then at some other predtermined value the TCV allows the pressure from the compressor (red hose) to vent outside via the blue hose.
Coorect so far? If not, how does it work?
when it fails, how does it fail? The pressure vents to blue all the time?

Post by **JDS60R** » 17 May 2012, 17:11

Its a pulse modulated solenoid. So it opens and closes like a fuel injector to get the right boost characteristics throughout the entire rpm range.
Red and yellow are correct. Blue goes back to the intake tube before the turbo. (No air is lost in these systems)

They tend to fail with the red and blue open (no boost) but most are replaced far ahead of failure time as the response is lowered with the age of the solenoid components. It has been common, to maintain peak performance to replace the TCV and boost pressure sensor at about 60 K miles. Many of them continue to perform great far after 60K. When Volvo started with actual boost pressure sensors the first design would often go bad by 60K. This is why many folks replaced them both.

Several of the Volvo systems do not use a dedicated boost pressure sensor . They are using the rpm, MAF etc to calculate a boost pressure.

I think the boost pressure sensors came in around 1999. On your T5R if you have over 100K miles I would replace the TCV with a real Volvo one from FCP. If the MAF is in spec and the oxygen sensors have been replaced every 100K you should do fine.

Post by **JDS60R** » 17 May 2012, 17:59

Kind of like this .

Cincyken · Post by **Cincyken** » 24 May 2012, 07:19

I think i have now figured it out.
The red to yellow is nornally open (NO)
the red to blue is normally closed(NC)
I did not know if mine was bad so i replaced it with a spare one i had for my S70 (slighly differnt design but the same operational characteristics and since my T5-R has a built engine from a 1998 S70 T-5, it should work, right).
The engine runs much smoother, and my gas mileage has gone up by about 10%. I would say that is a success story.
Thanks to y'all.

bugleg · Post by **bugleg** » 04 Jul 2012, 14:49

I have a 2000 V70XC with a low boost condition. Do I have a TCV and a boost pressure valve or are they one in the same?

KlubMarcus · Post by **KlubMarcus** » 08 Jul 2012, 18:44

bugleg wrote:I have a 2000 V70XC with a low boost condition. Do I have a TCV and a boost pressure valve or are they one in the same?

IIRC 1999 and newer have a separate Boost Pressure Sensor and Turbo Control Valve.

Amys 940 · Post by **Amys 940** » 08 Jul 2012, 23:59

I have a 98 v70xc. Does anybody have a vacuum diagram for my 2.4 turbo? Thanks!

Post by **abscate** » 15 Jun 2013, 10:20

Old thread alert - adding to this informative thread as I am diagnosing boost issues

My 1999 indeed has a "Manifold Pressure/Vacuum Sensor" also called a "Boost Pressure Sensor" located down on the Electronic Throttle Body (ETB) horn. Volvo part 9155870 - expensive part.

The Turbo Control Valve (also called the Boost Solenoid) is part 9155936 and is located up on the air cleaner box.

My vacuum hose diagram under hood actually does not match my solenoid at all, and shows the earlier '850 style' cylindrical can one. I have an early run 1999 car (OCT 1998 build date)

Post by **abscate** » 15 Jun 2013, 10:46

Here are the hose colours and assignments on the 1999 Turbo control valve, aka Boost Control Solenoid

Ive had this car since 2000, and I believe this is how it came from factory, so the color codings are probably factory too.

I made the assignments by tracing them - if someone with Volvo software could confirm that would verify this data.

Jamez123 · Post by **Jamez123** » 20 Jul 2013, 00:57

This article describes what the TCV does.
http://www.wothrline.com/Cars_engine/HW ... _valve.htm

Note that high performance TCV gimmicks can ruin your cars engine.

I installed an ARD unit in mine looking added performance like their selective testimonials only to fine it ran worst, it ran smoother and faster with my original. When it arrived it also came with a disclaimer on how it can ruin the engine that was not on their site. Of course they don't take it back and shipping cost almost as much as the part.

( so called high performance that did nothing, worst yet can break your engine)

I wished I read this article before buying this junk.

The article states:
"Later I have experienced that so called High Performance TCV's are becoming more common.
This is a unnecessary component that will cost money without adding anything to your car.
A TCV that is not behaving as the stock Volvo part may damage your engine.
Problems with boost control can be related to high performance TCV!"

As for routing:
http://www.vivaperformance.com/genuine- ... valve-tcv/
Red=Turbo Compressor nipple
Blue=Fresh Air hose
Yellow=Turbo Waste-gate nipple
Green=(does not attach to TCV) Intake Manifold to CBV only