Thank you for the information.

After I got the reply for you, I decided to give it the last try, found out the the volume switch in the faceplate had a short circuit, this masked all the another switches on the faceplate, after I separated the shorted contact pins and cleaned it, my headunit came back to life!!

Then after it accepted the code, it displayed E-3, after a full day of scratching head, I found the synthesizer IC SAA1057 in the receiver was dead, It screwed up the IIC bus, caused trunk mount receiver couldn't power on itself.

Removal of this IC temporarily solved the problem, I can use CD and cassette now, but without synthesizer, radio doesn't work. Hope I can find replacement part easily, I got the information from Philips semiconductor's home page, this chip was first release in 1983, hehe, hope they are still selling it.

Have a nice Christmas.

__________________
99 BMW 540i 6-speed 110K Km
03 SAAB 9-5 wagon 80K Km
92 400E (Sold) 245K km
Still missing the days with the Benz, it kept me busy.