I have the same stuff on my CD.

A constant reading of 53-64% suggests that the oil temp switch is making the brain think that the engine is still cold and is therefore keeping the system in open loop. Try unplugging the oil temp sensor so the brain does not get a ground signal, and see if the ratio starts to move around after the engine warms up.

The full sequence of tests for the emissions system is on the CD in 14-100 under the intake/exhaust manifold section.

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Chuck Taylor
Falls Church VA
'66 200, '66 230SL, '96 SL500. Sold: '81 380SL, '86 300E, '72 250C, '95 C220, 3 '84 280SL's '90 420SEL, '72 280SE, '73 280C, '78 280SE, '70 280SL, '77 450SL, '85 380SL, '87 560SL, '85 380SL, '72 350SL, '96 S500 Coupe