U1027 – Electric vehicle supply equipment (EVSE) (Nissan)

Nissan-specific code — factory diagnostic data

U1027 means your Nissan Leaf has a fault related to communication or status with the charging equipment you plug into. You will most often notice charging that will not start, stops early, or behaves inconsistently. According to Nissan factory diagnostic data, this code indicates an Electric Vehicle Supply Equipment (EVSE) issue as seen by the Charger/PD module. That does not prove the EVSE itself has failed. It tells you the vehicle detected an abnormal EVSE-related condition and set a network-type DTC to point you toward the charging interface, its signals, and the modules that interpret them.

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U1027 Quick Answer

U1027 on a Nissan Leaf points to an EVSE-related fault seen by the Charger/PD module. Diagnose the EVSE pilot/proximity inputs, related wiring/connectors, and module power/grounds before replacing parts.

What Does U1027 Mean?

Official definition: Electric vehicle supply equipment (EVSE). In plain terms, the Charger/PD module decided something about the external charging equipment interface did not look right. In practice, that usually means the car cannot confirm charging readiness, cannot maintain a valid charging session, or logs an EVSE-related network complaint even if you can still drive normally.

What the module is actually checking: the Charger/PD module monitors EVSE-related status and command information during plug-in and charge events. Depending on Leaf configuration, that includes the control and detect signals that indicate “plug present,” “ready to charge,” and “allow charge.” Why that matters: U-codes use intentionally general wording under SAE J2012-DA, and the DTC text does not identify a failed part. You must confirm which EVSE-related input, message, or circuit the module found abnormal, then prove the root cause with testing.

Theory of Operation

Under normal operation, the Nissan Leaf Charger/PD module manages the vehicle side of the charging handshake. It watches the EVSE interface state as you connect the charge coupler. The module then decides when to request and permit charging. It also shares charge status across the vehicle network so other modules can coordinate.

U1027 sets when that expected EVSE-related information becomes invalid, missing, or inconsistent for the conditions present. The problem can live outside the car, at the charge port, or inside the vehicle wiring and modules. A weak connection, water intrusion, or poor power or ground to the Charger/PD module can corrupt signals and create a network-type fault. Because the description stays broad by design, you must use scan data and circuit checks to narrow the exact failure path.

Symptoms

You will usually notice charging-related problems first, and a technician will see EVSE-related faults during a scan.

• Scan tool behavior Charger/PD module shows U1027, and EVSE/charge-status PIDs may flicker or disagree with the plug-in state
• Charging won’t start Plugged in but the vehicle does not transition to a charging state
• Charging stops early Session begins then terminates without a clear external cause
• Intermittent charging Works on some attempts, fails on others, often tied to connector movement
• Charge warning Charge indicator or EV system warning messages related to charging availability
• Reduced charge features Delayed charge or timer functions may fail because the vehicle cannot validate EVSE status
• Stored history Code may store as history after a single abnormal plug-in event, even if charging later resumes

Common Causes

• EVSE communication interruption: The Charger/PD module loses expected EVSE-related messaging or signaling and logs U1027 when the input becomes invalid.
• Open circuit in EVSE signal path: A broken conductor or backed-out terminal prevents the module from seeing the EVSE state change or handshake.
• Short to ground in EVSE signal wiring (FTB -11 pattern): Insulation damage or water intrusion pulls the line low and blocks valid EVSE signaling.
• Short to battery in EVSE signal wiring (FTB -12 pattern): Harness chafing to a power feed drives the line high and forces an implausible EVSE status.
• High resistance at connectors: Corrosion or loose pin fit drops signal quality and creates intermittent EVSE detection, often worse with vibration.
• Poor Charger/PD module power or ground: Voltage drop under load destabilizes the module and disrupts EVSE interpretation without a hard module failure.
• Network integrity fault affecting EVSE-related data: A CAN/LIN fault can block EVSE status sharing, causing the Charger/PD module to flag a network DTC.
• EVSE equipment fault or incompatible signaling: A failing charge cable/EVSE can output an invalid state that the Nissan Leaf interprets as a fault condition.

Diagnosis Steps

Use a scan tool that can read Nissan-specific DTCs, freeze frame, and network status for the Leaf. Have a quality DMM, a back-probing kit, and basic harness inspection tools. For network checks, use an ohmmeter function and access to CAN+ and CAN- at a convenient module connector. You will also need a known-good EVSE or a way to swap charge equipment safely.

1. Confirm U1027 in the Charger/PD module and record freeze frame data. Focus on ignition state, vehicle speed, battery voltage, charge/plug status, and any related U-codes. Note whether U1027 shows as pending or confirmed/stored, since two-trip logic can apply to some monitors.
2. Run a full network scan and verify the Charger/PD module appears online. Record any modules that do not report, plus all communication and power-supply DTCs. If multiple modules show network DTCs, treat this as a network or power problem first.
3. Check fuses and power distribution feeds for the charging system and related control modules before probing the Charger/PD module. Inspect fuse blades and fuse box terminals for heat damage. Verify the correct feeds power up in the correct ignition mode.
4. Verify Charger/PD module power and ground with voltage-drop testing under load. Command an operating state when possible, or key ON to wake the module. Accept less than 0.1 V drop on grounds during operation, because a clean continuity check can miss high resistance.
5. Inspect the charge inlet area and EVSE-related harness routing for water intrusion, impact damage, or prior repairs. Look for rubbed-through loom, pinched wiring, and green corrosion. Pay close attention to connector locks and terminal tension.
6. Disconnect and inspect the Charger/PD module connectors and any accessible EVSE/charge-inlet connectors. Check for pushed-out pins, spread terminals, moisture, and discoloration from heat. Reseat connectors fully and confirm the secondary locks engage.
7. Use the scan tool to review live data PIDs related to charging and EVSE status. Watch the data while you plug and unplug the EVSE, and while you manipulate the harness lightly. If the status flickers, you have a strong harness or connector fault direction.
8. If the Leaf uses CAN for EVSE-related status exchange on your platform, check CAN bus resistance with ignition OFF and the 12 V battery disconnected. Measure between CAN+ and CAN- at an accessible connector. A healthy bus reads about 60 ohms, while 120 ohms or OL points to an open or missing termination.
9. With ignition ON, check CAN bias voltage to ground at the same access point. You should see about 2.5 V bias on both CAN+ and CAN-, because the network bias only appears when powered. Do not use ignition-OFF readings as a reference for bias checks.
10. Perform targeted circuit tests on the EVSE signal circuits that the service information identifies for your Leaf configuration. Check for short to ground, short to battery, and open circuit from the Charger/PD module connector to the next inline connector. If the scan report includes an FTB suffix, use it to prioritize the test direction, such as -11 for short to ground or -12 for short to battery.
11. Differentiate freeze frame from a scan tool snapshot during an intermittent issue. Freeze frame shows conditions at the moment U1027 set. Use a snapshot you trigger while wiggling the harness or swapping EVSE equipment to catch brief signal loss events.
12. Clear DTCs and retest under the same conditions that set the code. Confirm the EVSE status stays stable in live data and U1027 does not return as pending after one trip or as confirmed after two trips, depending on monitor behavior.

Professional tip: Treat U1027 as a “suspected trouble area” code, not a parts verdict. On Nissan Leaf charging concerns, a small voltage drop on a ground splice or a lightly corroded connector can mimic an EVSE failure. Prove the power, ground, and signal integrity first, then evaluate the EVSE equipment with a known-good unit.

Possible Fixes

• Clean and repair corroded connectors: Remove moisture intrusion sources, restore terminal tension, and repair damaged pins after confirming the fault location.
• Repair harness damage: Fix chafed, pinched, or broken conductors in the EVSE/charge-inlet signal path, then verify stable live data.
• Restore proper module power and grounds: Repair high-resistance grounds, loose fasteners, or compromised power feeds found by voltage-drop testing.
• Correct a network fault: Repair CAN wiring opens/shorts or termination issues when resistance and bias checks prove a bus problem.
• Verify EVSE operation with a known-good unit: Replace or service the external EVSE/charge cable only after the vehicle-side circuits test good.
• Module replacement as a last step: Replace the Charger/PD module only after you prove correct powers, grounds, and inputs, and confirm the fault persists.

Can I Still Drive With U1027?

You can usually drive a Nissan Leaf with U1027 stored, but you should treat it as a charging-system warning first. This code points to the Charger/PD module losing expected communication or status information related to the EVSE connection. Driving may feel normal because the fault often shows up during charge events, not while cruising. The risk comes later, when you need to charge. The car may refuse to charge, stop charging early, or charge at a reduced rate. Do not ignore warning messages related to charging, the EVSE connection, or the high-voltage system. If the vehicle shows multiple charging faults, or it will not shift normally, stop and diagnose before continued use.

How Serious Is This Code?

U1027 ranges from an inconvenience to a major usability problem. If the Nissan Leaf drives normally and only fails to start a charge, this code mainly affects charging reliability. It becomes more serious when the Charger/PD module drops offline on the network, because other modules may also lose charger-related data. That can trigger reduced power modes or limit charging as a protective strategy. Treat it as higher priority if you see repeated charge interruptions, charging port warnings, or multiple U-codes across modules. Also take it seriously if the code returns immediately after clearing. A fast return often indicates an active network, power, ground, or connector fault.

Common Misdiagnoses

Technicians often replace the EVSE, charge cord, or charge port parts too early. U1027 does not prove the EVSE failed. It tells you the Charger/PD module did not see expected EVSE-related information. Another common mistake involves ignoring the SAE J2012DA FTB suffix -93. That suffix points to a specific fault type, so you should test for the matching condition before any parts. Shops also misread a “no charge” complaint as a charger failure and skip basic network checks. Confirm module power and ground under load, verify connector tension and corrosion, and check CAN/LIN integrity at the Charger/PD module before ordering components.

Most Likely Fix

The most common confirmed repair direction involves restoring a clean, stable electrical and network path to the Charger/PD module. That usually means correcting poor terminal tension, corrosion, water intrusion, or harness damage at the charger/EVSE-related connectors. A close second involves fixing a power or ground feed problem that causes the module to reset during EVSE handshake. Do not treat the charger module as failed until you verify power, ground, and network waveforms, and you confirm the EVSE signal path meets Nissan service checks. After repair, verify with repeated charge attempts and a road test that meets enable criteria for the related self-checks.

Repair Costs

Network and communication fault repairs vary by root cause — wiring/connectors are often the source, but module-level repairs or replacements can be significantly more expensive.

Last updated: April 10, 2026