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post #30 of (permalink) Old 09-13-2019, 02:50 PM
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rv6john's Avatar
Join Date: Mar 2013
Location: In the twisties around Hendersonville, NC
Posts: 8,004
I'm pretty sure that the CMP sensor is only used at starting and disregarded once the engine is running. Once it knows cylinder #1 is on TDC compression stroke, it can keep track with just the CKP sensor after that.

This is borne out by the Fail Safe chart in the service manual.

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I first became aware of this when working on my Aprilia SXV. It is a V-twin with only a CKP sensor. The ECM throws spark at both cylinders for about 20 seconds and then figures out which cylinder to fire by the pulse intervals. A not uncommon mistake on those engines would be to install the cams 180 degrees off. It would start just fine and run for 20 seconds

I just don't see how a faulty CKP could produce these codes on those two cylinders so consistently. Even the manual's possible "things to check" does not mention the CKP as a possible culprit.
"Ignition coil, wiring/coupler connection, power supply from the battery"

I know it has been checked, but my guess would be the that there is a poor connection on the O/W power wires to those two cylinders. At a certain rpm, it might just vibrate the poor connection enough to trigger the fault.

Originally Posted by Chuckster View Post
If you think reading is tricky, how the hell are you going to follow troubleshooting directions?
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