2007 XC70 loses almost all power while in Cruise control...

AylmerQc · Post by **AylmerQc** » 21 Jul 2025, 06:30

It has happened twice.
First time I was pulling away from a parking lot and onto a highway. Gunned it and put on the cruise control then realized I was too slow for traffic coming up behind me so I pressed the + repeatedly to increase my cruising speed. The car pretty much immediately lost all power and went into what I believe was limp mode as I pulled over onto the shoulder.
I turned it off and back on again and was able to drive away as if nothing had happened except there was a message on the side display of reduced engine power.
I drove it for a few months without any similar issues and eventually took the car to a reputable mechanic who reset the code and said he didn't find any problems although he said it may have been caused by an Air Mass flow issue...
Fast forward many months and yesterday I was cruising at 110kms going up a slight but long incline on the highway when the car lost power again.
I pulled over, turned off the engine and everything went back to normal. This time though there wasn't a Reduced engine Power message on the display.
Any suggestion on what's causing this?

Post by **Blacklab467** » 21 Jul 2025, 07:23

This is a somewhat common issue, I've had it occur several times and found other documented cases on this forum.
When it would happen on my 2003 XC70, the car would go into limp mode and not be able to exceed about 30 km/h. I would have to pull over and clear a P1354 code with my cheapy scanner before it would go back to normal. I would also get the REDUCED ENGINE PERFORMANCE message.
Each time this happened it was while the cruise control was engaged and being commanded to accelerate hard, going up a hill on the highway for example.
I've stopped using the cruise control permanently for fear of getting stranded in a remote location and requiring a tow.
As far as I recall, no one has been able to find a cause or solution for this issue.

Post by **Blacklab467** » 21 Jul 2025, 07:26

viewtopic.php?p=588399&hilit=limp+mode#p588399

This is a post that I wrote the first time it happened. Note that the code was a P1651. Good Luck!

Post by **br0dy519** » 21 Jul 2025, 07:59

Check your throttle body. Similar symptoms on my Bosch MY04 when it died.

Sweep test in VIDA, pos2 startup sequence, and of course clean it.

AylmerQc · Post by **AylmerQc** » 21 Jul 2025, 11:55

Thanks..
I understand what you've written except the Pos 2 startup sequence..?

Post by **br0dy519** » 21 Jul 2025, 13:59

From car off, put key into POS2, wait up to 90 seconds, it should do a test of the butterfly flap in the throttle body, you should actually be able to hear or watch it do it's sweep test.

Post by **jonesg** » 21 Jul 2025, 15:17

if it runs on the vacuum system, my old volvo did,
the brake assist vac pump might be providing too a weak vacuum.... or vac leak.

Brake position sensor will disable the system if bad or out of position.
Out of position will show as if the peddle is depressed and disengage the system.
viewtopic.php?f=9&t=33622

Post by **Krons** » 21 Jul 2025, 20:51

My 08 S60 was occasionally dying under power, was the fuel pressure sensor on the rail. Easy item to swap if you want to try it.

I initially diagnosed as torque converter going bad as it felt like transmission was coming out of gear. I seemed to recall it was somewhat tied to cruise control use…never happened without cruise on.

Post by **scot850** » 22 Jul 2025, 08:41

I'm not sure the 07 XC70 has the fuel pressure regulator on the rail. Our 06 XC70 and a friends 06 S80 2.5T both have the in the fuel pump in the tank.

Neil.

Post by **vtl** » 22 Jul 2025, 10:33

Read the codes with DiCE/VIDA, it will tell you what's wrong. A generic OBD scanner can't tell you the whole story.