Easy one-page printout for the garage or repair shop
This summary uses the existing diagnostic information shown in full below.
This code means that the car's computer has detected a problem with the part of the engine that measures how well the spark plugs are working. It's like if a video game controller wasn't getting enough power to work properly.
The P1390 code indicates that the voltage in the circuit responsible for measuring the ionic current, which helps monitor the spark plug performance, is below the expected level.
The ionic current voltage selection measuring circuit is part of the engine's ignition system. It monitors the ionization current in the combustion chamber, which is used to assess the quality of the combustion process. A low voltage in this circuit can affect the engine's ability to optimize ignition timing and fuel mixture, potentially leading to performance issues.
• Check Engine Light is on
• Poor engine performance
• Increased fuel consumption
• Faulty ignition coil
• Damaged wiring or connectors in the circuit
• Failed engine control module (ECM)
Ignition Coil: A component that transforms the battery's voltage to a higher voltage needed to create a spark in the spark plugs.
ECM: Engine Control Module, the computer responsible for managing the engine's functions.
• Use an OBD-II scanner to confirm the code.
• Inspect the ignition coil and related wiring for damage.
• Test the voltage in the ionic current circuit.
• Replace the faulty ignition coil.
• Repair or replace damaged wiring or connectors.
• Replace the ECM if necessary.
• OBD-II scanner
• Multimeter
• Wrench set
$150 - $500
Moderate
• Chrysler PT Cruiser
• Dodge Neon
• Jeep Grand Cherokee
• Regularly inspect ignition system components.
• Ensure all electrical connections are secure.
• Follow the vehicle's maintenance schedule.
Sensor Issue
• Have the vehicle inspected by a professional if the Check Engine Light is on.
• Avoid driving the vehicle aggressively until the issue is resolved.
Check with the vehicle manufacturer for specific warranty coverage related to the ignition system.
This code has been associated with ignition system issues in older Chrysler and Dodge models, often due to aging components.
Moderate – The vehicle may experience performance issues, but it is usually safe to drive to a repair shop.
Driving with a malfunctioning ignition system can lead to increased emissions and may be illegal in some areas.
• Engine running
• Vehicle at operating temperature
The ignition coil is typically located near the engine's spark plugs.
Q: Can I drive with a P1390 code?
A: It's generally safe to drive short distances, but you should have it checked as soon as possible to avoid further issues.
Q: Will a P1390 code affect fuel economy?
A: Yes, it can lead to increased fuel consumption due to inefficient combustion.
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Network faults often require full-system access instead of a generic code reader alone.
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Universal · Digital multimeter
A solid entry-level multimeter for voltage, continuity, resistance, and basic electrical troubleshooting.
Helpful for checking voltage drops, grounds, and basic circuit health when modules are not communicating.
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Universal · Wire connectors and repair kit
Useful when diagnosis points toward damaged wiring, corroded terminals, or connector repairs.
Useful if diagnosis points toward damaged connectors, wiring, or terminal repairs.
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Fitment Required · Vehicle-fitment part
Commonly relevant for misfire, ignition-efficiency, and some drivability-related repairs.
Misfire and ignition-related faults commonly involve spark plugs as part of the repair path.
Check the correct plug type, gap, and engine application for your vehicle.
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Fitment Required · Vehicle-fitment part
Relevant when the fault points toward ignition-coil performance or cylinder-specific ignition issues.
Some ignition faults involve coil performance or cylinder-specific coil problems.
Match the coil to your engine and confirm the failed component before ordering.
View options on AmazonThese parts may be related to this fault category, but a code by itself does not confirm exact fitment or guarantee that replacing a part will solve the problem.