Hard Trouble Code E18
NOTE:
If this code is not displayed during second pass of diagnostic codes, it is an intermittent failure and cannot be diagnosed using this procedure.
While engine is cranking, a 12 volt signal will be present in cranking circuit from ignition switch to ECM. Trouble code indicates that the 12 volt signal is not present at ECM while engine is cranking. Possible causes of this condition are: An open 3 amp crank fuse, defective wiring, terminals, etc., defective theft starter interrupt relay, defective Park/Neutral switch, or ECM not processing signal properly.
NOTE:
The following step numbers refer to the numbers in the accompanying flow chart(s).
- Check 3 amp crank fuse. If it is blown, check circuit No. 806 for short to ground between fuse and ECM. If circuit is okay and fuse blows again, then short must be in ECM connector or ECM itself.
- If fuse is okay, check voltage at crank fuse while cranking engine. If fuse has 12 volts on it, then check for voltage on circuit No. 806 at ECM, again while cranking engine. If 12 volts is measured then, check pin 1 terminal for an open before replacing the ECM. If no voltage is measured at ECM, repair open in circuit No. 806 between fuse and ECM.
- If there is no voltage at crank fuse, check voltage, while cranking engine, on circuit No. 5x at theft starter interrupt relay. If voltage is 0 volts, then open exists in circuit No. 6 between theft starter interrupt relay and ignition switch.
- If circuit No. 5x has 12 volts on it, then check voltage on circuit No. 5 at ECM while cranking engine. If voltage is 0 volts, then an open exists within theft starter interrupt relay; therefore, theft interrupt relay should be replaced.
- If circuit No. 5 has 12 volts on it, then check voltage, while cranking, at Park/Neutral switch. If voltage is 0, then an open exists on circuit No. 5 between theft starter interrupt relay and Park/Neutral switch.
- If circuit No. 5 has 12 volts on it, then check voltage on circuit No. 6 at Park/Neutral switch. If voltage is 0, then open exists in the Park/Neutral switch. Replace Park/Neutral switch.
- If circuit No. 6 has 12 volts on it, then open exists in circuit No. 6 between Park/Neutral switch and 3 amp fuse.