RAM 2500 Truck 2WD L6-5.9L DSL Turbo VIN 6 (1998)
Tachometer: Description and Operation
SYSTEM OPERATION
The tachometer gives an indication of the engine speed in revolutions-per-minute (RPM). The instrument cluster circuitry controls the gauge
pointer position. The instrument cluster circuitry calculates the proper gauge pointer position based upon engine speed messages received from the
Powertrain Control Module (PCM) on the Chrysler Collision Detection (CCD) data bus.
The PCM uses an input from the crankshaft position sensor and internal programming to calculate what engine speed messages are required. The
PCM then sends the proper messages to the instrument cluster on the CCD data bus. The crankshaft position sensor is a hall-effect sensor installed
near the rear of the engine, where it is aimed at the trigger wheel attached to the rear flange of the crankshaft.
