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EV Charging Diagnostic Tool

Won't charge, charging slowly, or seeing a charger error? Pick your symptom and get an instant diagnosis of the most likely faults — on-board charger, charging port, home wallbox, DC fast charger and BMS charge logic — plus a free expert call. Works on every EV brand.

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11+ charging faults26+ fault codesAC & DC · Type 2 · CCS2 · GB/T2W · 3W · 4W · any brand

Free diagnosis

What's your EV charging problem?

Pick the symptom that matches what you're seeing — we'll instantly show the most likely faults and offer a free expert diagnosis, for any EV brand.

Every EV charging fault, diagnosed

Symptoms, root causes, how we fix it, and the related fault codes — for the charging faults we see most across every EV brand.

No charging — dead charge session

criticalNo charging

The EV does not begin charging at all when plugged in — no charge light, no progress. The fault can be anywhere from the supply socket to the BMS charge-enable signal, so a structured trace beats swapping parts.

Symptoms

• No charging indicator when plugged in
• Works on one charger but not another
• Sometimes starts after re-plugging

Common causes

• No / low supply voltage at the socket or wallbox
• Control-pilot (CP) handshake not established
• Failed on-board charger (OBC) or its relay
• BMS refusing to enable charging (12V, SOC or fault)
• Damaged charging-port pins

How we fix it

• Verify supply voltage and earthing at the socket
• Test the cable / gun on a known-good charger
• Read OBC and BMS charge-enable status over CAN
• Inspect and clean the charging-port contacts

PILOT_NO_SIGNALOBC_INPUT_UVBMS_CHG_DISABLEGet a free fix

12V / auxiliary battery preventing charge

mediumBMS / battery

A weak 12V auxiliary battery is one of the most common reasons an EV 'won't wake up' to charge. The 12V system powers the contactors and charging logic; if it is flat, the high-voltage charging never enables.

Symptoms

• Car seems dead or slow to wake
• Intermittent no-charge
• Other 12V gremlins (lights, infotainment)

Common causes

• 12V battery aged or discharged
• DC-DC converter not topping up the 12V
• Parasitic drain from accessories

How we fix it

• Test and charge / replace the 12V battery
• Verify DC-DC output (~13.5–14.5V running)
• Run a parasitic-draw test if it keeps discharging

BMS_CHG_DISABLEGet a free fix

Slow / reduced charging speed

highSlow charging

Charging is happening but far below the rated kW. The cause can be the charger, the cable, a degraded port contact, BMS throttling, or thermal / cold limits — measuring real kW throughput isolates the bottleneck instead of guesswork.

Symptoms

• kW far below rated
• Slower than it used to be
• Slow on DC but normal on AC (or vice-versa)

Common causes

• BMS thermal or cold throttling
• High resistance at the charging-port contacts
• Charger / cable rated lower than the car
• Single-phase supply where 3-phase was expected
• High pack temperature

How we fix it

• Measure delivered kW vs the rated speed
• Thermal-image the port and connector under load
• Compare AC vs DC behaviour
• Check and service the port contact resistance

BMS_CHG_DERATEPORT_CONTACT_RESBMS_CHG_OVERTEMPGet a free fix

On-board charger (OBC) failure

criticalCharger / OBC

The on-board charger converts AC to DC to charge the pack. When it fails the car won't AC-charge, may trip mid-charge, or throw OBC fault codes; water ingress and surge damage are frequent root causes.

Symptoms

• No AC charging (DC may still work)
• Charging trips out within minutes
• Burnt smell near the charger
• OBC fault code present

Common causes

• Surge / spike damage to the OBC
• Water ingress into the module
• Internal relay or rectifier failure
• Lost CAN communication with the OBC

How we fix it

• Confirm AC fails but DC works (isolates the OBC)
• Read OBC fault codes and live data
• Measure OBC input and output under load
• Board-level repair where feasible, else replace + add surge protection

OBC_INPUT_UVOBC_OUTPUT_OVOBC_OVERTEMPOBC_COMM_LOSSOBC_RELAY_FAULTGet a free fix

Charging port / inlet damage

highPort / cable

The charging inlet takes mechanical and thermal stress every plug-in. Loose, corroded, melted or cracked pins cause no-charge, slow-charge, overheating, or a gun that won't lock.

Symptoms

• Melted, discoloured or corroded pins
• Gun won't lock / clicks repeatedly
• Hot to touch while charging
• Intermittent connection

Common causes

• Repeated arcing from a loose contact
• Water / dust ingress and corrosion
• Locking-actuator failure
• Physical damage

How we fix it

• Inspect and measure pin contact resistance
• Clean contacts or replace the inlet to OEM spec
• Repair / replace the locking actuator

PORT_OVERTEMPPORT_LOCK_FAULTPORT_CONTACT_RESGet a free fix

Charging cable / connector fault

mediumPort / cable

A damaged Type-2 cable, portable charger or control-pilot fault in the gun can stop charging or cause intermittent drops. Often mistaken for a car fault.

Symptoms

• Works on another cable but not this one
• Visible cable damage or burnt pins
• Portable-charger LED error

Common causes

• Damaged or kinked cable
• Control-pilot (CP/PP) resistor fault
• Burnt / arcing connector pins

How we fix it

• Swap-test with a known-good cable
• Inspect both connectors for damage
• Repair / replace the cable or gun

PILOT_NO_SIGNALCP_FAULTGet a free fix

AC home charger / wallbox — no output

highHome / AC

A home wallbox that powers up but delivers no charge, or trips the breaker, usually has a supply, earthing, RCBO or internal-relay issue. Installation faults are a frequent root cause.

Symptoms

• Wallbox powers on but won't charge
• Trips the MCB / RCBO on start
• App shows fault / won't pair

Common causes

• Incorrect or missing earthing
• RCBO / GFCI tripping on leakage
• Internal contactor welded or failed
• Under-rated supply wiring

How we fix it

• Verify supply, earthing and RCBO type / rating
• Test the wallbox contactor and PCB
• Correct installation faults

EVSE_NO_POWEREVSE_RELAY_WELDEVSE_GFCI_TRIPGet a free fix

DC fast charger handshake / sequence failure

highDC fast

DC fast charging needs a digital handshake (CCS PLC / GB-T CAN / CHAdeMO) before the contactors close. A failed handshake, isolation check or timeout stops the session before any power flows.

Symptoms

• DC session aborts before charging
• Works on AC but not DC
• Fails only at certain DC chargers

Common causes

• PLC / CAN communication dropout
• HV isolation fault flagged pre-charge
• Sequence timeout / version mismatch
• Charge-port or pilot fault

How we fix it

• Capture the DC abort code
• Test on a second DC charger
• Measure HV isolation resistance
• Check pilot + PLC/CAN communication at the inlet

DC_HANDSHAKE_FAILDC_ISOLATION_FAULTDC_TIMEOUTGet a free fix

Charge stops at 80% / won't reach 100%

mediumBMS / battery

Stopping near 80% can be normal (a set charge limit or DC taper) or a real BMS balancing / SOC-estimation issue. Diagnosis confirms whether it's a setting or a fault.

Symptoms

• Always stops near 80%
• SOC jumps near the top
• Long time to add the last few %

Common causes

• Charge limit set in the app
• Normal DC taper above 80%
• Cell imbalance triggering early cutoff
• SOC estimation drift (LFP flat curve)

How we fix it

• Check the app charge-limit setting first
• Run a full slow AC balancing charge
• Read individual cell voltages for imbalance

BMS_CHG_CUTOFFBMS_CHG_IMBALANCEGet a free fix

Overheating during charging

criticalSafety / earth

A charger, cable or port that becomes very hot — or any burning smell — is a safety risk. Stop charging immediately. Causes range from a loose contact to a cooling or BMS fault.

Symptoms

• Connector / port too hot to touch
• Burning smell or discolouration
• Charging derates or stops from heat

Common causes

• Loose / high-resistance contact arcing
• Under-rated socket or wiring
• Battery cooling fault
• OBC thermal fault

How we fix it

• Stop charging and disconnect at the source
• Thermal-inspect the full path (socket → cable → port)
• Repair the contact / cooling / OBC fault

PORT_OVERTEMPOBC_OVERTEMPBMS_CHG_OVERTEMPGet a free fix

Earth leakage / RCD trips while charging

criticalSafety / earth

An RCD / RCBO that trips when charging is detecting current leaking to earth — a genuine safety device doing its job. It must be diagnosed, never bypassed.

Symptoms

• RCD / RCBO trips on plug-in or mid-charge
• Trips only when charging, never otherwise
• Mild tingle on the body (stop immediately)

Common causes

• Insulation breakdown in OBC / wiring
• Moisture in the charging port or cable
• Wrong RCD type (needs Type A or B)
• Faulty wallbox earth

How we fix it

• Insulation-resistance test the charge path
• Dry / repair the port and cable
• Fit the correct RCD type and repair the earthing

EVSE_GFCI_TRIPPORT_CONTACT_RESGet a free fix

EV charging fault codes reference

Generic charging-related fault codes across the on-board charger, BMS charge logic, charge port, control/proximity pilot, EVSE and DC fast charging. Exact strings vary by manufacturer.

Code	System	Description	Severity	What to do
OBC_INPUT_UV	OBC	On-board charger input under-voltage	high	Check supply voltage and earthing at the socket; test on a known-good charger.
OBC_INPUT_OV	OBC	On-board charger input over-voltage	high	Check mains stability; surge events can damage the OBC — inspect for damage.
OBC_OUTPUT_OV	OBC	OBC DC output over-voltage	critical	Stop charging. OBC regulation fault — service diagnosis required.
OBC_OVERTEMP	OBC	On-board charger over-temperature	high	Allow to cool; check OBC cooling. Repeated faults need inspection.
OBC_COMM_LOSS	OBC	Lost communication with on-board charger	high	Check 12V supply and CAN to the OBC; hard reset, then diagnose.
OBC_RELAY_FAULT	OBC	OBC input relay welded / open	critical	Do not keep charging. OBC relay failure — service required.
BMS_CHG_DISABLE	BMS	BMS charge-enable not asserted	high	Check 12V battery, SOC and active BMS faults; read the charge-enable flag.
BMS_CHG_CUTOFF	BMS	BMS early charge cutoff	medium	Confirm the charge-limit setting; run a balancing charge; check cell voltages.
BMS_CHG_OVERTEMP	BMS	Pack over-temperature during charge	high	Allow cooling; verify battery cooling system operation before charging.
BMS_CHG_OVERVOLT	BMS	Cell over-voltage during charge	critical	Stop charging. Possible cell imbalance / BMS fault — service required.
BMS_CHG_IMBALANCE	BMS	Cell imbalance limiting charge	medium	Run a slow AC balancing charge; read individual cell voltages.
BMS_CHG_DERATE	BMS	Charge power derated by BMS	medium	Usually thermal or cold. Precondition the battery; recheck under normal temp.
PORT_OVERTEMP	PORT	Charge port over-temperature	critical	Stop charging. Loose / high-resistance contact — inspect and repair the inlet.
PORT_LOCK_FAULT	PORT	Charge port locking-actuator fault	high	Gun won't lock; charging is blocked. Test / replace the lock actuator.
PORT_CONTACT_RES	PORT	High charge-port contact resistance	high	Causes heat and slow charge. Clean or replace the inlet contacts.
PILOT_NO_SIGNAL	PILOT	No control-pilot (CP) signal	high	Handshake cannot start. Test the cable and the inlet CP circuit.
CP_FAULT	PILOT	Control-pilot duty / level fault	high	Check the cable / EVSE CP signal and the inlet CP circuit.
PP_FAULT	PILOT	Proximity-pilot (PP) resistor fault	medium	Cable not detected correctly. Inspect the PP resistor / connector.
EVSE_NO_POWER	EVSE	Wallbox / charger no output	high	Verify supply, earthing and the wallbox contactor / PCB.
EVSE_GFCI_TRIP	EVSE	Charger earth-leakage (GFCI/RCD) trip	critical	Real leakage detected. Insulation-test the charge path; never bypass the RCD.
EVSE_RELAY_WELD	EVSE	Wallbox contactor welded	critical	Charger cannot isolate safely — stop use and replace the contactor.
EVSE_OVERTEMP	EVSE	Charger / wallbox over-temperature	high	Check ventilation and connector seating; inspect for loose terminals.
DC_HANDSHAKE_FAIL	DC	DC fast-charge handshake failed	high	Try another DC charger; check pilot + PLC/CAN comms at the inlet.
DC_ISOLATION_FAULT	DC	HV isolation fault before DC charge	critical	Leakage detected pre-charge. Insulation-resistance test required.
DC_TIMEOUT	DC	DC charging sequence timeout	medium	Comms / version mismatch. Retry; if persistent, diagnose the charge-port comms.
AC_PHASE_LOSS	EVSE	AC phase missing (3-phase supply)	high	Charging limited or stopped. Check the supply phases at the wallbox.

Connectors & charging standards

The standards we diagnose and repair, with their most common faults.

Type 2 (AC)

Mennekes 7-pin AC connector — home & public AC charging up to 22 kW.

• Control-pilot (CP) handshake faults
• Proximity-pilot (PP) resistor errors
• Pin burn / arcing from loose contact
• Locking-actuator failure

CCS2 (DC fast)

Combined AC + DC connector for fast charging up to 350 kW.

• DC handshake / sequence timeout
• HV isolation fault before contactor close
• Temperature derate / pin overheating
• PLC communication dropout

GB/T & Bharat AC/DC

Common on Indian and Chinese-origin EVs and many 2W/3W.

• GB/T DC sequence & CAN faults
• Bharat AC-001 socket / RCBO issues
• Connector corrosion in humid climates

CHAdeMO & 3-pin

Legacy DC fast standard; 3-pin domestic 'granny' charging.

• CHAdeMO CAN handshake errors
• 3-pin overheating / undersized wiring
• No earth / loose neutral at the socket

EV charging safety

High voltage & mains warning

DC fast charging and the EV's on-board charger handle 300–800 V DC, and home charging runs on mains AC. Never probe a charging port or open an OBC without isolation, insulated tools and training. If you smell burning or see a melted connector, stop charging immediately and disconnect at the source.

• A dedicated RCBO (Type A or B) is mandatory for AC charging.
• Never charge via an extension board or undersized socket.
• A warm plug is normal; a hot or discoloured plug is not.
• Repeated MCB / RCD trips indicate a real fault, not a nuisance.
• Earth-leakage trips, burning smells or HV isolation codes → call a technician.

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EV charging — frequently asked

My EV won't charge at all — what do you check?

We diagnose from the wall socket inward: supply voltage and earthing, the charging cable / gun, the charging port, the on-board charger, and the BMS charge-enable logic. You get a clear cause and a fixed-price repair — no guesswork.

Do you repair and install home AC chargers / wallboxes?

Yes — installation, no-output faults, RCBO / earth-leakage trips, and app or Wi-Fi pairing for 3.3 kW and 7.4 kW home units across all major brands.

Which connectors and standards do you support?

Type 2 (AC), CCS2 (DC fast), GB/T, CHAdeMO and Bharat AC-001 / DC-001, plus standard 3-pin domestic charging.

Which EV brands does the tool cover?

Every brand — Tata, MG, Mahindra, Hyundai, Kia, BYD, Ola, Ather, TVS, Bajaj, Hero, Ampere and more — across 2-wheelers, 3-wheelers and cars. EV charging faults are largely brand-agnostic.

Can you fix slow charging?

Yes. Slow charging usually traces to the charger, cable, a degraded port contact, BMS throttling or thermal limits. We measure actual kW throughput to isolate the real cause instead of swapping parts.

Is the diagnosis really free?

Using the tool is free, and an ev.care expert will call you back within 2 hours for a free assessment. The site-visit fee is waived when you go ahead with the repair.

Diagnosed it? Let's fix it.

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