Hyundai Ioniq: Engine Electrical System / Troubleshooting

Hyundai Ioniq (AE) 2017-2025 Service Manual / Engine Electrical System / Troubleshooting

Trouble Shooting

Ignition System

Symptom	Suspect area	Remedy
Vehicle indicates Ready in dash, but engine will not run when requested by the HPCU (HEV module).	Ignition coil	Inspect ignition coil, or replace as required
	Spark plugs	Inspect spark plugs, or replace as required
	Ignition wiring disconnected or broken	Repair wiring, or replace as required
Rough idle	Ignition wiring	Repair wiring, or replace as required
Rough idle	Ignition coil	Inspect ignition coil, or replace as required
Engine hesitates / poor acceleration	Spark plugs and spark plug cables	Inspect spark plugs / cable, or replace as required
Engine hesitates / poor acceleration	Ignition wiring	Repair wiring, or replace as required
Poor mileage	Spark plugs and spark plug cables	Inspect spark plugs / cable, or replace as required

Charging System

Symptom	Suspect area	Remedy
Charging warning indicator does not light with Start/Stop Button "ON" and Hybrid System off.	Fuse blown	Check fuses
	Light burned out	Replace light
	Wiring connection loose	Tighten loose connection
	LDC problem	Check the LDC. Refer to HC group
Charging warning indicator does not go out with Hybrid System on. (Battery requires frequent recharging)	Battery cable loose, corroded or worn	Inspect cable connection, repair or replace cable
	LDC problem	Check the LDC. Refer to HC group
	Wiring	Repair or replace wiring
Overcharge	LDC problem	Check the LDC. Refer to HC group
Overcharge	Voltage sensing wire	Repair or replace wiring
Discharge	Wiring connection loose or short circuit	Inspect wiring connection, repair or replace wiring
	LDC problem	Check the LDC. Refer to HC group
	Poor grounding	Inspect ground or repair
	Worn battery	Replace battery
	Abnormal parasitic draw from the vehicle	Install a current probe to measure current. It should be less than 0.05A (50mA) after Hybrid System off and waiting 10 minutes. Make sure trunk light is removed for this test.

Starting System

Symptom	Suspect area	Remedy
Vehicle will not indicate Ready in dash at Hybrid System on.	Auxiliary 12V battery charge low	Charge or replace auxiliary 12V battery
	Auxiliary 12V battery cables loose, corroded or worn out	Repair or replace cables
	Transaxle range switch (Vehicle with automatic transaxle only)	Refer to AT group-automatic transaxle
	Fuse blown	Replace fuse
	Ignition switch faulty	Replace

Specifications

SpecificationsIgnition System Items Specification Ignition coilPrimary resistance0.56 Ω ± 10 %Spark plugsTypeELR9ISP8+Gap0...

Other information:

Hyundai Ioniq (AE) 2017-2025 Owner's Manual: Aux. Battery Saver+ was used while parked, Switching to Hybrid mode to allow heating or air conditioning (Plug-in hybrid vehicle)

Aux. Battery Saver+ was used while parked (Plug-in hybrid vehicle) This message is displayed when the Aux. Battery Saver+ function has been completed when the vehicle is turned ON. Switching to Hybrid mode to allow heating or air conditioning (Plug-in hybrid vehicle) This message is displayed when the vehicle automatically switches to HEV mode to allow heating or air conditioning...

Hyundai Ioniq (AE) 2017-2025 Owner's Manual: Closing the fuel filler door

1. To install the fuel tank cap, turn it clockwise until it "clicks" one time. 2. Close the fuel filler door until it is latched securely. WARNING Gasoline is highly flammable and explosive. Failure to follow these guidelines may result in SERIOUS INJURY or DEATH: Read and follow all warnings posted at the gas station...