Download 2004 Hyundai Sonata No Spark Problem & Service Manual – 1. At the crank position sensor, check for battery voltage to be present on the Red wire with the key on and cranking. The Black wire should be a good ground and the Blue wire should have 5 volts on it from the computer. One may have to disconnect the crank sensor to check for the 5 volt reference. 2. During crank look for a good 5 volt square wave signal on the Blue wire. 3. Check at the ignition coils for good battery voltage key on and cranking. If there is a loss of voltage during crank check the ignition failsafe relay. 4. Check for any stored engine codes. Crankshaft Position (CKP) Sensor Ignition Failsafe Sensor The ignition failsafe sensor supplies battery voltage to the ignition coils. The ignition coils can look like they have good battery voltage key on but during crank the ignition failsafe relay can stop sending voltage to the ignition coils.