B418

Code B418 - Loss Of Crank Signal To BCM:

Wiring Diagram for Code B418 - Crank Signal Circuit Problem:

CODE B418 - CRANK SIGNAL CIRCUIT PROBLEM

Circuit Description:

Code B418 will set when the ignition is on, engine RPM is greater than 640 and the crank signal input (CKT 805 from the 3A crank fuse) is still or never did go HI (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. CKT 805, crank signal input, is HI (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.



Test Description:

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 BCM.


Note on Intermittents:

If an intermittent Code B418 is being set, check for an intermittent open in CKT 805 to BCM or poor terminal contact at BCM 1C9.