ECM Code EO18 - Open Crank Signal Circuit: Notes

TEST CONDITIONS:  Engine RPM greater than or equal to 800.

FAILURE CONDITIONS:  No crank signal has been received by the ECM since the last time that RPM was zero RPM (engine started, ECM didn't register a crank signal).

ACTION:  ECM turns on "ENGINE CONTROL SYSTEM" light. ECM commands BCM to display "SERVICE SOON" message on CCDIC panel. Code is stored as current for entire key cycle.

The crank input signal to the ECM is an on/off signal that comes from the starter solenoid, through the 3-amp crank fuse, and then to pin "B3" of ECM. During crank, the signal is battery voltage, at all other times signal is zero volts.

Code EO18 is set if the ECM detects engine running at 800 RPM or more without having crank input go to system voltage.

1. DO NOT use this procedure if EO18 is a history code. See NOTE ON INTERMITTENTS.
2. If circuit No. 806 becomes grounded, the crank fuse will blow when engine is cranked.
3. This branch of diagnostic chart tests for ECM's or BCM's ability to short crank input signal to ground.
4. Voltage signal to crank fuse comes from ignition switch, through theft starter interrupt relay, and the park/neutral switch. This branch checks for opens between crank fuse and starter solenoid.