Ignition Switch Circuit Open
Table of contents
U300A MERCURY Possible Causes
- Faulty Ignition Switch
- Ignition Switch harness is open or shorted
- Ignition Switch circuit poor electrical connection
- Faulty Body Control Module (BCM)
How do I fix code U300A MERCURY?
Check the “Possible Causes” listed above. Visually inspect the related wiring harness and connectors. Check for damaged components and look for broken, bent, pushed out, or corroded connector’s pins.
Cost of diagnosing the U300A MERCURY code
The cost of diagnosing the U300A MERCURY code is 1.0 hour of labor. The auto repair labor rates vary by location, your vehicle’s make and model, and even your engine type. Most auto repairs shops charge between $75 and $150 per hour.
Possible Symptoms
- Engine Light ON (or Service Engine Soon Warning Light)
U300A MERCURY Description
Conventional Ignition Switch:
The ignition switch is a multiple position rotary switch that is controlled by a lock cylinder and a key. The ignition switch provides voltage to the ACC, ON, or START-designated circuits depending on the position it is placed. The Body Control Module (BCM) calculates the positions based on the voltage received from the ACC and ON-designated circuits.
The key removal inhibit solenoid (also known as the key release interlock actuator) is an electronically controlled solenoid that prevents the ignition lock cylinder from being turned to the OFF position unless the gear selector lever is in the PARK position. The key removal inhibit solenoid is part of the ignition switch.
Push Button Ignition Switch:
The push button ignition switch is used instead of a conventional ignition switch to achieve the various ignition modes. The push button ignition switch is a momentary dual contact switch. Both sets of contacts are normally open and receive the voltage at all times. When the START/STOP button is pressed, the voltage is sent to the BCM, the RFA module, and the PCM to indicate a button press.
The ignition switch has a LED for switch illumination when the backlighting is activated.
