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Q: Turbo Control Valve , Engine Control Module on 2001 Volvo V70


I think I need a Turbo Control Valve = TCV and hoses for my 2001 Volvo V70 2.4 front wheel drive. I am not getting power when pressing on the gas pedal and it wants to stall. The car runs fine when first started but after it warms up and it is shut off it will stall when restarted and their is a lack of power (sometimes). If I keep the RPM's up by depressing the gas it will run (I have not tried to drive it this way). I already replaced the Mass Air Sensor and that did not help. I had my local Volvo dealership run a diagnostic test and they found "communications faults" with the ABS control module , the central electronic module , the Engine Control Module = ECM (Volvo wanted to replace the ECM wiring harness, they said they found some corroded terminals) and they wanted to replace the turbo control valve.

I was going to start with replacing the turbo control valve and do it myself.

1. Do these problems sound like a turbo control valve gone bad? or a plugged or worn out hose on the TCV or both?

2. Do you have a tutorial on the TCV replacement and it''s hoses I can view?

3. Do you have a tutorial on replacing the ECM wiring harness ?

Thank you for all of your help.
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When there is a fault with the Turbo Control Valve, the turbocharger will be disabled, leaving you with very poor acceleration.
The turbo valve is very easy to replace, disconnect the electrical connector and remove the sensor from the intake pipe.
I don't think you're getting good info, what I would do is get the diagnostic trouble codes, post them here and I can help you out. Throwing parts at it is a waste of money, as you found out by replacing the MAF sensor.
Hey Aduzi,
At this point you really need to get the diagnostic codes read out. You may be able to have this done at a parts store, some do it for free. I would like to see the fault codes erased first, then drive the car until the check engine light comes on (it is coming on right?) then check the codes, and post them here and then I can give you some advice.
Make sure all the intake hoses and pipes are not leaking, and make sure the intercooler at the front of the car has not been damaged from a rock or a curb, this will cause a large air leak in the intake system!
Let me know what you find!
Hi Aduzi,
This sure sounds like it has an air leak somewhere in the intake system. Have you checked this really good like I mentioned before? Look real good by the throttle body, the shop that replaced it may have left a hose loose.
Where did you purchase the parts? Are they Volvo parts or aftermarket?

Here are the code descriptions:
P1238 - Turbocharger (TC) control system flow Fault, Flow too high
P0171 - Long-term fuel trim, Upper limit
You can visually inspect all the intake hoses and pipes with the vehicle on the ground. Check to see they are all installed correctly and are not loose. Make sure the turbocharger intercooler is not damaged.
If you cannot find any problems, then I'd say it's time to go to a professional. These type of problems require some special tools and knowledge to diagnose. You put some good effort into this, but you may now be introducing more problems.
Good Luck, let me know what happens!
Hello munkyrench,

Thank you for the response. As soon as I am able (probably this week ) I will pick up the TCV at my not so local Volvo Dealership (30 miles away). When I install it, do you recommend any hose replacement? After the deed is done I’ll let you know how it turned out.
Sorry I did not get any of the codes. The dealership replaced the Electronic Throttle Module (under warranty). After the ETM was replaced, the dealership told me the car had other issues and took it upon themselves to run another diagnostic test. I was able to get them to tell me what showed up on the test but did not get the codes as I was not charged for the second diagnosis. The first diagnosis for the ETM was under warranty.

Thank you again for the response.
Hello ,

The new TCV has been installed and the car still has issues. It seems that the RPM's are not consistent and the car is prone to stalling. Once the car gets going the RPM's will level out and the car runs well. The car seems to start when cold, OK but once warmed up RPM's become an issue (they drop below 1 on the tachometer)
and then stall. If by depressing the gas pedal and keeping the RPM's up the car will eventually get back to running OK.
Any suggestions?

Thank you,
Hello munkyrench,

Great to hear from you! The dealership must have erased the fault codes when they replaced the Electronic Throttle Module because the check engine light came back on today. I was able to stop at an Advance Auto where their diagnostic equipment read P1238 Fuel Air Metering and P0171 System too lean bank 1.

Just a reminder, I had already replaced the “Mass Air Sensor” and the “Turbo Control Valve”. The dealership replaced the Electronic Throttle Module, cleaned the crankcase ventilation and downloaded software to initialize to vehicle.

The car runs OK (not a lot of pep). When it is started from a cold start, once warmed up and restarted it needs to have the RPM’s kept up (with a little brake/gas peddle foot action) until it gets going and then it runs OK until it is shut off then restarted while warm. The cycle then starts over.

Looking forward to your response.
Thank you,
Hello munkyrench,

The TCV is Volvo and the Mass Air is a Bosch that replaced a Bosch (could I have gotten a bad Air Mass Sensor or maybe not have needed it in the first place? The old TCV had a broken clip and was laying under the air box. There was one missing hose clamp on the TCV and I am wondering if it maybe was exchanged while in the shop. I'm also wondering if the hoses were switched. I thought not at first because the hoses were very hard to get off. Could one of the hoses be bad? A mechanic at a Volvo dealership said not likely, could the waste hose be clogged? It seems as if the turbo is kicking in or could that just be normal acceleration?

I'll look at the intake again but it is hard to tell what I am looking at. Is it possible to see all the connections from under the hood or does the car need to be up in the air?

Thank you again,
Hello munkyrench,

There is a short piece of rubber hose 3-5 inches long that is attached directly to the manifold and some other hoses that connect to the intake plastic pipe ( about 3 inch diameter). Anyway this small piece of hose has two clamps that I do not think are tight enough because I can spin this hose on the nipple from the manifold and whatever else it is connected to with my fingers. Should this hose be tighter and not movable? The clamps look like none I've seen before and probably need a special tool to tighten them.

If the intercooler is viewable thru the grill and I'm not looking at the radiator, then it appears to be OK.

This will be my last attempt at fixing it before I bite the bullet.

Does this sight have eMail or a more direct line that we can communicate thru? My eMail address is

Thanks for all your help,
Hei i get the code 6805 Boost presure Control.Have change alredy the turbo Control valve but the car making the same problem Power desapire over 2000prm?Kan you help me?Regards
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