cruise control triggers limp mode

[93Regina]

I doubt that is a load issue

I'm just a "red-blocker," but doing a Google search with these words, "limp mode cruise volvo," brings up lots of posts on Volvo, and some VW forums. It seems OP never finds an answer on these forums.

There are a number of things that might trigger this issue, but it seems fuel/air/ignition issues are possible candidates...when hard acceleration under cruise control kicks engine into limp mode.

A code reader might narrow this issue down, but my gut feeling, via several posters' comments, is a temporary lean condition exists, which kicks engine into limp mode. It could be due to crack vacuum line, to clogged air filter, MAF off calibration, to brake booster's check valve, to a computer not getting correct inputs from various sensors, or computer sending out commands but output sensors are not responding correctly.

I'd have to see a listing of all the input/output sensors/etc, with a description of their functions, but I suspect something is bringing about a lean condition.

Btw, on this 2001 V70 XC, what type of code reader would be used for real time info? Does VIDA DICE give "live" info? IF so, I'd watch O2 readings and knock sensor(s) and take a test drive.

[abscate]

A lean condition will trip a CEL as the fuel system is continuously monitored. Paul definitely has/ had something electronic in nature going on

His cruise control switches input directly into the ECU, so if he had a short in that switch or a low voltage condition, that would trigger limp mode

[93Regina]

A lean condition will trip a CEL as the fuel system is continuously monitored.

I'm somewhat literate on GM and Bosch EFI systems, upto 1993 era. In short, the ECU (aka black box) calls the shots, which means its computer program determines when to turn on the CEL, and normally, OEMs don't detail their EFI systems, so we don't have the operational specifics of when/how codes are tripped.

Under this condition, limp mode happens when CC is doing a power acceleration, this topic has come up, over and over.

In a VW forum, one person stated ..." Everything electrical was replaced and nothing fixed the problem and that is why with 3k on the clock the car was purchased back by VWoA," OP stated at end of thread...."The code I got was for overboost. The dealer ended up replacing my fuel sensor but that didn't solve the problem. I ended up replacing the improperly sized Fujita intake (at the maf sensor) and replaced it with a Neuspeed P-Flo and this issue has not resurfaced, although I rarely use CC." In another VW thread, OP suggested..."i just talked to the dealership and they are saying that its a recall in a fuel sensor."

As I've learned from EFI systems, a code may point to the cause, or it can point to the effect. And, many mechanics have wasted millions and millions of dollars fixing the effect first, and not the cause when using a code-reader.

I assume VW and Volvo were both using Bosch's EFI...true/false? Again, does VIDA DICE give "live" info?

[abscate]

It's a classic case of the Internet causing the demise of expertise. Being able to read codes and replace parts does not make one a five rivers expert, it makes one a decent technician, like me.

OBD guides you to the repair about 90% of the time, the other 10% you needed either an expert or collective experience like MVS

[93Regina]

...the other 10% you needed either an expert or collective experience like MVS

Or, in Paul's case, omit this step:

"3) press + (accelerate button) on steering wheel"

Interesting, I have around a million miles driven, the old fashion way, without cruise. I never have cruise issues...never

Btw, I like this write-up...it all makes sense...ETM issue...5-cylinder engine in models produced in 1999, 2000 and 2001.

Signs of a failing ETM and its relation to the MAF sensor

[abscate]

I've found cruise very effective even in heavier traffic. I set up at about 15 percentile speed ( 65 mph in NY, 70 in NJ orvMA) and. Stay stress free in right lane