Code B418, Crank Signal Circuit Problem (Riviera Only): Notes

Code B418 will set when the ignition is on, engine speed is above 640 RPM, and the crank signal input (circuit No. 805 from the 3 amp crank fuse) is still or never did go high (system voltage). These conditions cannot be observed, as the purpose of the crank input is to signal the BCM to shut off when cranking so that voltage variations that are normal during crank do not affect the electronic devices. Circuit 805, crank signal input, is high (system voltage) when the ignition switch is in the crank position. If this code sets, fix this problem before trusting any other codes that may have set, as erratic voltages during crank could cause false setting of codes.

1. Checks for intermittent condition.
2. Checks if loss of crank signal is due to an open or short in the circuit.
3. Checks if blown fuse was caused by intermittent short to ground.
4. Checking continuity at various points will determine which branch of the circuit is shorted.
5. Checks to see if the open circuit reading is due to the circuit or the BCM.