Volvo: ETS light coming on... -20 C / gas tank half full, mass air flow sensor, mass air flow

Question
Hello Vedat,
Thanks in advance for taking the time to answer my
question.
1999 Volvo S70 , 100,000 miles.
Repair history...only standard replacements thus far as well
as some front suspension issues...nothing electronic thus
far.
So, the basic problem, as I am sure you know with ETS
issues, is the light comes on, there is some 'choking' in the
engine with some near stalling in an idling state (i.e.
stopped at a light).  This issue has happened now on two
trips...the tank was half full (I use only premium fuel - 91
octane) and the temperature was -20 C or even colder on
both occasions.  To solve the problem I filled the tank
up...my thought at the time was that the fuel was freezing
in the lines...not enough gas getting in...and therefore the
near stalling...I have since come to think that the issue may
not be so simple.  I am wondering what might be going on,
if this is a serious issue,  and whether or not I need to take
it in immediately.
I hope that I have provided enough pertinent information...

Again thank-you for your input.  It is greatly appreciated,
Sincerely,
Julian

Answer
Hello Julian,
Firstly I should say that unfortunately this case is important so you should get the car repaired as soon as possible.
ETS means Electronic Throttle System, the problem is regarding that part. The part is located in the inlet side of the engine that means it is a part of inlet side of the emission system, also there is one part called mass air flow sensor it is located also at the inlet side of the engine. There are two parts also called oxygen sensors (one of them is front oxygen sensor the other one is rear) located on the exhaust, they are parts of the emission system. If you drive this car more with ETS problem, you may face to face oxygen sensor and mass air flow sensor problems also.
Firstly, please take the car to the service, the ETM (Electronic Throttle Module) should be cleaned, if the cleaning procedure will not be enough, it should be replaced with new one. Its price approx 750 USD. It has also a Software (ETM Software).
Briefly, go to service as soon as possible. At the service, the car will be checked via computer, and the Diagnostic Trouble Codes will be taken from the Engine Control Module. In my opinion they are regarding ETM according to your clues. Firstly, cleaning (if not enoughh) may be replacing...
Regards...