Riviera V6-231 3.8L VIN L SFI (1991)
Crankshaft Position Sensor: Description and Operation
Dual Crankshaft Sensor
Cam Sensor Circuit
The ECM/PCM uses this signal, through the C3I ignition module, to calculate engine speed and crankshaft position. The ECM/PCM compares pulses on
this circuit to any that are on ground CKT 453, ignoring any pulses that appear on both. The ECM/PCM also uses the pulses on this circuit to initiate
injector pulses. If the ECM/PCM receives no pulses on this circuit, no fuel injection pulses will occur and the engine will not run.
Circuit 453 is a ground circuit for the digital rpm counter inside the ECM/PCM, but the wire is connected to engine ground only through the ignition
module. Although this circuit is electrically connected to the ECM/PCM, it is not connected to ground at the ECM/PCM. The ECM/PCM compares
voltage pulses on the reference input CKT 430 to any on this circuit, ignoring pulses that ground on both. If the circuit is open, or connected to ground at
the ECM/PCM, it may cause poor engine performance and possibly a "CHECK ENGINE" light with no code.
