Well, tried again with engine not running, just ignition "ON", with the built in blinker light, got codes 4, 10 and 26. This time pressing the built in button to clear and turning off key for 2 seconds, then wait 10 seconds, then crank semed to remove the CEL. So my blink light box or my timing may have been off on the reset.

Can I expect code 4 (air pump system ) to keep happening, is there some sort of functional test being run and the lack of pump clutch current or performance is noticed?

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91 300 TE 235K
93 Cabriolet 155K sold
92 300 TE 200K boneyard