by ptommo59 on Sat, 20 May 2023 11:51 +0000
Hi Gulfcountry,
The TACH signal is generated by the Engine ECU and as you indicated technically could be based on inputs from the Crank Angle and/or Camshaft Sensors but I don't have access to a definitive source that explains how the ECU works.
However having a quick look at the 1KD-FTV Failsafe Chart if you lose the Crank Angle Sensor the engine will shut down but if you lose the Camshaft Sensor it will only limit power. Based on that I would think that the Crank Angle Sensor is the primary source for the TACH signal as this is required for multiple functions of the engine, transmission, dash gauges, etc.