What's Missing Here? VW Diesel (No Start)
A 2013 Jetta Diesel has a crank/no start condition. The engine will occasionally start, but rarely runs for long. The cam sensor has been replaced by the customer's shop as it tested bad.
First, two codes were pulled related to cam sensor performance and signal. There were no relevant data PIDs in relation to CMP sensor data, only RPM, which really isn't an issue.
Since all indicators pointed toward the cam sensor, next step is to scope the sensor to observe the waveform pattern. using a wiring diagram, the correct wires were located at the sensor. All three wires, 5V reference, ground, and signal return were all probed. The difference in scope patterns between a running and crank/no start became immediately became obvious, giving a good frame of reference between the two.
The 5V reference and ground pull up about half of an amp, which is normal during starter operation. By zooming in on the CMP pattern, we can compare it to a known good pattern.. When the patterns were compared, it became obvious that there was a small pulse missing on the problem vehicle. The segments on the cam were inspected, revealing all to be intact, leaving only one other possibility, the cam sensor!
The (new) cam sensor was replaced with an OE sensor, and the problem was solved!
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