mgd-98.5A4

It's been a while since I posted last, but I still own my 98.5 A4. Just passed 200k and almost 17 years of ownership.

Question. I just had my ABS module repaired by Module Masters. While the module was off the car and "in the mail" to/from Module Masters, the car sat in the garage - I didn't try to drive it. Today, after I installed the repaired module, I went to start it to see if the ABS/brake lights would go back to normal, and the car acted like it had a very low battery. Checknig the battery voltage it was at 9.5 volts. There were no problems at all prior to removing the ABS module - the car would sit for several days without any problems. So.... could having the ABS module unconnected for several days have drained the battery? I don't see others in the forum having a similar problem, but I'm blessed with poor search skills... Or, does this sound like a coincidental second problem that has just recently showed up? I'd rather it be something related to the ABS module disconnection since that "problem" has been solved now. But, if not, it's time to look at current draw and pin point what's now draining the battery. Audi ownership is always exciting and never boring!

Thanks,

Mike

AudiMick

You can't drain a battery by having something disconnected.

An A4 draws about 35-50 mA in standby ,even when the car is turned off, a brand new battery will discharge in 1000-1500 hours .

More likely is that you have an old battery with a couple of dead cells , you should be on your third battery by now since 7 years is about what they would last. Try charging the battery first, then check your alternator to see if you are getting 13.5 + volts out .

If you have a voltmeter that has a 2000 mA range you can check the current draw. Disconnect the + battery cable and connect your meter in series Make sure the lights are off and don't start the motor as you will fry that meter ,you should see around 150mA or so for less than a minute after you remove the key, it should then drop into standby mode.


I had an iPod adapter on my daughters A4 that didn't ever turn off with the ignition , drained the battery in 7 days if she didn't drive the car . If she drove it every day it was fine.

mgd-98.5A4

Thanks for the response! Yes, this is the 3rd, or 4th, battery in this car. This battery, an Interstate MTP-91, is under two years old.

I topped up the cells with distilled water before recharging the battery. The charge went well and the battery is holding a charge fine now. Yes, it's lifetime has likely been compromised somewhat. The alternator is putting out around 14 volts, and the dash voltmeter matches what my multi-meter shows. I don't have a 'clamp' style amp meter, so I had to disconnect the battery to check the current draw. Current draw dropped to 12-13 milliamps with everything off (which I'm told is normal for a 1998 A4). Note, I have no aftermarket electrical devices added to the car; it's essentially stock.

So, I had a few theories on what caused the battery to drain over several days. I'm in software development and when I investigate a problem I like to ask 'what happened just before the problem appeared?'. In this case, before I removed the ABS module, I used VCDS to scan and ensure the ABS codes were still the same. I then cleared all the DTC codes. During the clearing process, the radio did something very weird - it went into SAFE mode. I'd never had that happen during previous scans/clears. This scan and clear was done with version 14.10. I updated to 14.10.1 prior to the scans mentioned below.

Today, I scanned the car again. Scan showed a 01206 code in the HVAC system. Going into the Radio block, VCDS had trouble connecting to it due to "a high amount of errors". When clearing the codes, the radio reported no codes or inability to connect. Hum.... I pulled the fuse for the Radio to remove it from the equation and scanned again. Nothing was found - no modules connected at all. Hum.... I did the test under the VCDS options page and found the K1 line was shorted to ground. Aha!! I removed the Radio from the car and scanned again. All problems are gone - all remaining modules connect and show no codes. I'll rescan after a few drives to verify the HVAC code doesn't reappear.

So, I think my radio crapped out during the first set of scans and (theory time...) created a larger load on the battery while the ABS module was getting repaired. Then, when I disconnected the battery to charge it, the Radio reset itself so that there was a normal amperage draw (12-13 milliamps) when I measured it. Scanning again made the radio grumpy again, and that's when I saw the K1 short to ground problem.

My path forward now is to replace the radio. The ABS module was repaired successfully by Module Masters and is good to go.

Here are the scan codes I got so others can compare if they are in a similar situation. Note, the 01206 is likely a red herring - it was probably caused by the problems in the Radio.

Auto HVAC:
01206 - Signal for Duration of Ignition Off Time
27-10 - Implausible Signal - Intermittent

Radio:
No Faults Found
or DTCs not supported by controller
or a communication error occurred