I've done this many times in the past without problems, but suddenly I can't seem to get the 8-pin diagnostic module (X92) to work right. This is a Calif version with push button and red LED. (1988 260E with 103 motor.)

KOEO, hold the button 2-4 seconds and read the pulses. One pulse means everything's OK, no stored codes. But today, the red LED shows a steady light as soon as the key is turned on, and no amount of holding the button causes the LED to flash or to go off. Why is the LED on continuously, and how do I get it to turn off so that I can perform the pulse tests?

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1988 California version 260E (W124)
Anthracite Grey/Palomino
Owned since new and still going strong and smooth
MBCA member

Past Mercedes-Benz:
1986 190E Baby Benz
1967 230 Inherited from mom when she downsized
1959 220S Introduced me to the joys of keepin' 'em goin'

There are only 10 kinds of people in the world--those who understand binary and those who don't