Fault light came on today. - BAS/ASR malfunction indicator l

[steveperry]

Well I was driving to work this morning, my intermittent aircon fault was in full effect so that the air was going full blast & heat with the two aux fans  infront of the rad going at full speed too. :angry:

I was crawling in traffic going uphill, so holding the the car on the accelerator, when the BAS/ASR malfunction indicator lamp decides to light up My foot wasn't near the brake pedal when the lamp came on.

I drive for a couple of miles then stop behind some red lights, I took the opportunity to switch off and remove key for approx 30 seconds. Switch back on and the light remained off for the rest of the trip and never came on again for the rest of the day.

I remember reading in the hand book "If the electrical voltage drops below 10 volts, the malfunction indicator lamp will also light up in the instrument cluster and the Brake Assist System (BAS) will be de-activated."

I'm guessing this was the cause of my light illuminating today given my a/c was like a jet in take-off and must have been taxing the battery but my question is will the car ECU keep a log of this particular fault? Also will it log the fault indefinitely until someone links up with diagnostic software?

Sorry for the long post.
Any thoughts Andy?

Thanks,
S.

 

[rpalmeida]

Fault light came on today.

Lots of ecus in the car will log the undervoltage fault, and keep it until the ecu's fault log is reset. I imagine most ecus will lose their log when the power is removed..

 

[Arnie]

Fault light came on today.

The faults are normally stored in NVRAM or EEPROM and in this case, the log is not affected by disconnecting the battery.

Most electronic equipment in cars will work over a 9v - 18v range, but if your battery voltage has dipped too low then this could cause a system to temporarily malfunction and register a fault.

Shouldn't worry though, as most ECUs will disregard (erase) faults if they haven't re-occured for a while.

 

[Andy]

Fault light came on today.

Hi Steve

Replace the brake light switch. This should sort the problem.

Regards

Andy @ www.mercedesservicing.com

 

[steveperry]

Fault light came on today.

Thanks for all the information guys,

I feel a little happier that some expensive system isn't about to go critical on me.

cheers,

S.