From Ross-Tech Wiki
16705/P0321/000801 - Engine Speed Sensor (G28): Implausible Signal
- Engine shuts off
- Engine doesn't start
- Speedometer inoperative
- Glow Plug Indicator Lamp (K29) flashes
- Engine Speed Sensor (G28) loose
- Engine Speed Sensor (G28) faulty
- Check Engine Speed Sensor (G28)
- The Engine Speed Sensor (G28) is also used as a reference sensor for the crankshaft position and correlates with the Camshaft Position Sensor Bank 1 (G40) and Camshaft Position Sensor Bank 2 (G163).
- When an engine will not start due to mechanical (spark/fuel/compression/timing) related issues it is not uncommon to set a false G28 fault codes due to extended cranking with a no-start condition.
- When found in a VW Golf/Jetta (1J/9M) or Audi A3 (8L) with 1.9l TDI-PD (AXR), check TPI 2007067 which explains issues with electro magnetic interference. A modification to the wiring will fix this problem, extensive details can be found in the named TPI. Even though this TPI was originally released for VW Golf/Jetta (1J/9M), a customer of ours came across the same issue on an Audi A3 (8L).
- When found in a 2004 VW Golf, Jetta, or New Beetle with 1.9l TDI-PD (BEW), check for TSB 2010461 (01-07-45 formerly 97-05-03) or 201463 (01-07-44 formerly 97-05-04) calling for a flash update to the ECU and a secondary ground installation.
- General note for any engine type: Check the wiring to/from the sensor and engine control module to rule out harness and module damage due to engine oil or coolant from a failed sensor or tensioner. This is an example from a 2012 Tiguan with Coolant in the ECM which resulted in G28 DTCs in addition to intermittent stalling.