Turbo Code Help 2007 XC70 - 126C: boost pressure sensor-signal too high

[TempXCGuy]

At this point I would start with replacing/inspecting vacuum lines going to the waste gate actuator and TCV. IpD is selling great silicone hoses for this(i believe it was $20). If no leaks in the hoses, I would move to check if waste gate actuator is still working(hand held vaccum brake bleeder might be of help). Might want to remove waste gate connector and inspect if it moves freely. If you are already there you already inspected short upper turbo hose that goes to the Intercooler for cracks. If that all checked good...I would try to look for an oem wiring diagram and focus on MAP. I think it is a 3 wire sensor. Dont quote me, but i think it should be on 5v reference(1 wire), constant ground(usually 3rd) and sensor/feedback wire (2nd wire). At times you might get short to power or short to ground with those aging wires. Interesting if it is a hard fault vs occurring after several drive cycles. Great idea to smoke test everything. Good luck

Thank you for the information. I haven’t checked the hoses between the TCV and turbo and waste gate, but I will. Major noob question here (I’m just not that familiar with turbo cars), the line going to the waste gate provides pressure and not vacuum, correct?

I’ll check wires at the MAP. I have “mapped” the output on the MAP sensor on my scanner (Autel) and it is fairly consistent until I’m accelerating. Then it spikes and drops quickly, usually results in a code shortly there after and dump of most boost produced from that point forward. I should say, it spike, then stabilizes. I will monitor voltage as well though, I’ve been watching boost.

The waste gate does move freely, but again it’s under pressure and not vacuum.

Thanks again!

ok , a quick test , reach in and tug lightly on the rubber coupler sleeve that connects the turbo output to the charged air pipe that goes over the engine. They can get loose and blow off under boost, dumping the boost, then get sucked back into place again when the wastegate dumps the boost, you're non the wiser until you pull on the pipe and comes off.

If thats not the problem, robert spinner has a video about volvo turbo operation.

That video cleared up some things I think. I’m now thinking I have an over boost condition. The back story here is that I bought this car with a blown motor, so I hadn’t driven it up until recently. Given that, I have no idea what it’s supposed to feel/sound like. The turbo was supposedly new before the engine failed, so I didn’t do anything with it other than inspect it for shaft play.

I just got a smoke machine, so I’m going to complete checking for leaks tomorrow, but will verify the waste gate is functioning properly. The other thing I’m not sure about is whether I’m getting proper pressure going into the TCV to support movement of the waste gate. Any ideas on how to check this?

Thanks again!

[TempXCGuy]

What reader are using? Make sure the codes map to the correct Volvo code in Vida

It’s an Autel MaxiCOM MK808S. Can you explain your last sentence please? Been a mechanic for a long time, but this is my first experience with a Volvo.

Codes come in two varieties (that I know of)... look at this page and you'll see what I mean https://www.matthewsvolvosite.com/volvo ... wer-codes/

That is very good to know. I’m used to seeing P codes and others. Was a little thrown off by what I was seeing with the Autel, but also hadn’t dug into it yet. Thanks for that!

[jonesg]

I use an analog vac/press gauge to monitor the turbo.
https://www.ipdusa.com/products/10122/I ... Y1xqPT59Db

[TempXCGuy]

No turbo leaks to speak of. There was a very small one at the hose that connects to the throttle body. Easy fix with a little snug if the clamp. I’ve ordered a pressure/vacuum gauge and am going to check the pressure coming out of the turbo to the TCV. As I mentioned before, I’m now suspect that I don’t have any or maybe not enough pressure to activate the waste gate. More to come.

[TempXCGuy]

What reader are using? Make sure the codes map to the correct Volvo code in Vida

It’s an Autel MaxiCOM MK808S. Can you explain your last sentence please? Been a mechanic for a long time, but this is my first experience with a Volvo.

Codes come in two varieties (that I know of)... look at this page and you'll see what I mean https://www.matthewsvolvosite.com/volvo ... wer-codes/

I’m not finding either of these codes in that list. I have 126C and 601C

[matthew1]

I'd poke around in that Autel's menu to look for a way to switch code standards.

Google:

Q»
what kind of codes does autel use?

A»

Autel scan tools utilize standard OBD-II codes, including generic (P0, P2, P3, and U0), manufacturer-specific (P1, P3, and U1), and pending codes. These codes are used to diagnose and troubleshoot issues with a vehicle's engine and other systems. Additionally, Autel scan tools can display freeze frame data, I/M readiness status, and DTC definitions.

[TempXCGuy]

I'd poke around in that Autel's menu to look for a way to switch code standards.

Google:

Q»
what kind of codes does autel use?

A»

Autel scan tools utilize standard OBD-II codes, including generic (P0, P2, P3, and U0), manufacturer-specific (P1, P3, and U1), and pending codes. These codes are used to diagnose and troubleshoot issues with a vehicle's engine and other systems. Additionally, Autel scan tools can display freeze frame data, I/M readiness status, and DTC definitions.

Good suggestion, I’ll try that!

[TempXCGuy]

I wasn’t really able to work on the car this past week. But I’ve been poking around today and have some information.

I’ve checked all lines and pipes in and out of the turbo, TCV, and waste gate and have no leaks anywhere. I still need to monitor voltage and signal out of MAP, so that’s on my to-do for today or tomorrow. I wanted to see what pressure I was getting out of the TCV to actuate the waste gate so I connected a pressure gauge inline between the TCV and waste gate. I also pressurized the line with compressed air and noted that the waste gate doesn’t really move at all until it sees about 10psi. Does that seem right?

Also, the MAP is new but reads about 14 psi whether the car is idling or off. I assume it’s reading atmospheric pressure and that I can consider the 14 psi as 0 psi in terms of boost pressure (25 psi observed in scanner is the same as 11 psi boost)?

Ok, I went for a test drive with pressure gauge connected and scanner, trying to watch them both as I drove. I noted that it pulls good up to about 10 psi (observed both on gauge and scanner), then you can feel the waste gate open and if I stay in it, it’ll recover and continue to pull. My gauge only goes to 10 psi so it’s hard to know how much pressure I’m getting there.

Finally, I’m reading at most about 30psi (16psi) on the scanner. Does that seem right in terms of maximum boost on this car?

Does it make sense that you’d really feel the waste gate open, resulting in a noticeable loss in power. Not massive, but definitely noticeable, not smooth.

Sorry for the long message guys and thanks again for the help!

[jonesg]

I get 5 psi turbo pressure. Never feel the wategate blow off.
Its supposed to be a low pressure turbo, has it been changed ? tuned ?

[matthew1]

^ that was my thought. Tune, bigger turbo, IPD CBV kit, etc.