Already disconnected, I removed the CIS-E control unit from the car. I unscrewed the black case covering the innards. Inside on my hobby bench, I examined the double circuit board arrangement to determine which board could be freed to allow examination of the components upon them. The lighter green board populated by integrated circuits was carefully separated by removing two screws and unlocking several plastic bayonet post mounts. I carefully unfolded the two boards on their shared ribbon-cabled hinge. Using the inspection methods recommended for the ISCU went it becomes internally suspect, I looked at the components for any signs of overheating or bad solder joints. A few questionable solder welds were reheated with an small-tipped iron. Overall, the stuff inside my CIS-E looked good.

With the sounding continuity feature enabled, I attempted to trace the circuitry from the connector pin assigned to connect with B11/2. The related components looked good, and so did there solder welds. I did the same thing with the pin that outputs the TF Signal to the ISCU. Again, nothing signficant was noted.



Back in the car, I reconnected the naked and unfolded CIS-E. I successfully measured continuity from the B11/2 sensor wire plug to the backside of the CIS-E's mounted connector. With this additional access to the connections within the CIS-E, I confirmed and performed a few more electrical checks from the previous test groups. Nothing remarkable was found. I duplicated the previously failing TF Signal test and got two measurements of 0.50V and 0.57V.

As the engine continued to warm-up, I repeatedly measured the voltage input from B11/2 at the CIS-E's pin 21 and the output from pin 9. When the temperature stabilized at 159 degrees F (70 deg C) the two values converged at 0.46V. At that time, I realized that the manual's specification (3.5 - 5.0V) and my measurement were off by an order of magnitude. Could it be that the manual contains another (potentially the third for me in two days) typographical error? Can anyone confirm the correct output voltage of pin 9 for a 1986 560SL's CIS-E?

I realize on hindsight, that the engine was not warm enough the tests I performed today. I will be repeating several tests again tomorrow, and definitely double-checking if B11/2 is affecting the idle speed.