Volvo Repair: 1999 Volvo V70XC ETS Light, mass air flow, volvo xc

Question
I have recently purchased a 1999 Volvo XC with 71k miles.  The car runs fine, but after only 125 miles of use the ETS light came on and stays on whenever the car is running.  No other warning lights (engine, etc) are on and the car seems to run fine (no stalling or rought idle, etc). I've driven about another 50 miles without incident other than the light being on.   All the owners book says is that it's the Engine Throttle System light and to take it to the dealer....can you give some idea of what this problem might be?   I have been using regular (89 octane) gas vs. the premium that is suggested in the owners guide.  Could that cause this problem?

Answer
Hello,
Firstly, I should say that do not use 89 octane use 92 or more.
Then, ETS (Electronic Throttle System) faulty is a serious faulty. The car should be checked as soon as possible. ETM (Electronic Throttle Module)is a part of the engine emission system, located at the inlet side, and also at the inlet sided there is one "brother" of it, Mass Air Flow(MAF) sensor, they work together. The other brothers of the emission system are located on the exhausr, oxygen sensors, all of them work together, inlet side and exhaust side affect eachother. So that means if there is a problem on one of them the other ones can be affected, because of this reason please do not drive the car more with this faulty, as soon as possible get it checked.
Te problem can be ETM itself. Firstly, to clean the ETM will be helpful, if you have no problem regarding stalling, rpm decreasing&increasing or powerloss. Also, there is Software for ETM, ETM Upgrade. This SW will be helpful for this car after cleaning. If the faulty is more serious than I guessed maybe ETM replacement will be necessary.
Also, I should say that if your car has manual gearbox, under clutch pedal there is a sensor, clutch pedal sensor, sometimes this (ETS) lamp lights because of this sensor's faulty. (However, as percentage I can give you 95%possibility of the ETS light is ETM, 5% is the other affects, like clutch pedal sensor)
Regards...