2022 Hyundai HECU Module Dark Current Measurement TSB

Important Warnings

Hyundai has issued specific instructions and warnings for dealers and owners regarding this service campaign:

• Dealers are required to perform this service campaign on all affected vehicles before customer retail delivery and whenever an affected vehicle is in the shop for any maintenance or repair.
• "Do not “Start” the engine at any time during the test procedure. Doing so will yield inaccurate dark current measurement results."
• "If the door is open while in standby, sleep mode will not activate."
• If the "ABS", "ESC", or "Brake" indicator lamps are illuminated, technicians must refer to the appropriate section of the repair manual before performing this TSB inspection.
• "All claims submitted that have incomplete, illegible, or missing documentation are subject to debit."
• "Claim is subject to debit if the part is not returned."
• "All part orders are on manual allocation."

Symptoms

Owners of certain 2022 Hyundai Elantra (CN7A), Sonata (DN8A), and Santa Fe (TMA) vehicles may observe the "Electronic Parking Brake (EPB) warning light on" in the instrument cluster. This symptom is often accompanied by Diagnostic Trouble Code (DTC) C1501, which indicates an "EPB Switch Failure." Despite the warning light, the EPB system's performance typically remains unaffected.

Fault codes / DTCs

This issue is primarily associated with the following diagnostic trouble code:

Code	Description	Module
C1501	EPB Switch Failure	HECU

Diagnosis / Trigger Conditions

The root cause of the "Electronic Parking Brake warning light on" and DTC C1501 is brake fluid ingress into the HECU electrical connector, leading to an excessive Hyundai HECU dark current draw. To diagnose this, technicians must measure the dark current draw from the HECU module. The vehicle must be in sleep mode for an accurate measurement, which means all doors should be closed and the ignition off for at least 3 minutes. It is crucial not to start the engine during this test, as it will lead to inaccurate readings.

Maximum dark current values vary by model and engine type:

• Elantra (CN7A) and Sonata (DN8A): 95 µA
• Santa Fe (TMA) 2.5L: 95 µA
• Santa Fe (TMA) 2.5T: 105 µA

Repair Procedure Summary

The repair process involves measuring the Hyundai HECU dark current to determine if the HECU module needs replacement. Here's a summary of the steps:

1. Preparation: Record the customer's radio presets. Turn off the vehicle, close all doors, and wait at least 3 minutes for the vehicle to enter sleep mode. Disconnect the negative battery terminal and remove the junction box fuse cover.
2. Multi-fuse Removal (Sonata/Santa Fe): For Sonata (DN8A) and Santa Fe (TMA) vehicles, remove the 10 mm multi-fuse mounting nut and both multi-fuses. Reinstall one multi-fuse to leave a specific space open for dark current measurement, then reinstall the mounting nut.
3. ABS Fuse Removal (Elantra): For Elantra (CN7A) vehicles, use a fuse puller to remove the 40A ABS fuse.
4. Multimeter Setup: Reconnect the negative battery terminal. Set the multimeter (DT-830D+) to the 200 µA setting. Ensure the multimeter's internal fuse is intact. Connect the black probe to the appropriate ABS fuse location and the red probe to the positive battery terminal.
5. Dark Current Measurement: Measure the dark current for at least 30 seconds, ensuring the reading remains consistent. Take a photo of the multimeter reading and the open junction box for documentation (STUI), including the last 6 digits of the VIN and the repair date.
6. Decision and Action:
   • If the measured dark current is below the maximum specified value, reinstall all removed parts in reverse order. No further action is required.
   • If the measured dark current is equal to or above the maximum specified value, replace the Hydraulic Electronic Control Unit (HECU) according to the shop manual. After replacement, take another photo of the newly installed HECU and the removed original HECU for documentation.
7. Final Steps: Reassemble the vehicle. Start the engine, confirm that the "ABS", "ESC", and "Brake" indicator lamps are not illuminated, clear any incidental DTCs, and reprogram the customer's radio presets.

Required Tools or Parts

Technicians will need the following specific tools and parts for this procedure:

• Multimeter: DT-830D+ (Part Number: HK589-DT830QQH)
• Hydraulic Unit Assy ESCI+ (HECU):
  • Elantra (CN7A): 58910-AB800QQH (supersedes 58910-AB800)
  • Sonata (DN8A): 58910-L0100QQH (supersedes 58910-L0100)
  • Santa Fe (TMA) 2.5L: 58910-S2DA0QQH (supersedes 58910-S2DA0)
  • Santa Fe (TMA) 2.5T: 58910-S2GA0QQH (supersedes 58910-S2GA0)

Owner Action

If you own a 2022 Hyundai Elantra, Sonata, or Santa Fe and are experiencing an "Electronic Parking Brake warning light on" or suspect an issue with your Hyundai HECU dark current, you should contact your authorized Hyundai dealer. This is a service campaign (990), meaning it should be performed free of charge. Dealers are instructed to perform this service on affected vehicles prior to retail delivery and during any maintenance or repair visit. You can also check the