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Protocol guide

CCS handshake basics

Find where SLAC, CableCheck, PreCharge, or CurrentDemand dies, then branch.

CCS handshake basics

When you use this / what it is not

Use this when a CCS1/CCS2 DC session fails before useful current, fails at CableCheck/PreCharge, or drops during CurrentDemand with protocol-looking symptoms. Audience: field techs who can read CP/PP with a meter and pull CSMS session timelines.

This is not:

  • DIN 70121 / ISO 15118 stack source code or a PLC Wireshark course
  • An OEM pinout for every handle on the market
  • Permission to probe HV DC with a $20 meter and hope
  • A vehicle OEM diagnostic procedure (you validate with a second EV; you do not reflash the car)

If the cabinet is already StatusNotification Faulted with GroundFailure before plug, start with the OCPP Faulted map — handshake never started.

How handshake failures present

Display / LEDs

  • “Initializing,” “Communicating,” “Preparing,” then error or silent return to idle
  • Lock engages then releases within seconds (SLAC/SDP fail)
  • Lock stays, display spins, no kW — stuck in CableCheck/PreCharge
  • LEDs: blue/white “session” then red; some OEMs flash connector LED during PLC

OCPP / CSMS

  • Preparing → Available with no StartTransaction (auth never completed or EVSE aborted)
  • StartTransaction with 0 kWh Stop a minute later
  • vendorErrorCode: SLAC, SDP, CableCheck, PreCharge, CurrentDemand, Timeout, Isolation
  • MeterValues never leave 0 A / 0 V (or show bus voltage then collapse)

Vehicle side (driver report)

  • Car screen: “Charging station error,” “Compatible station not found,” “Check connection”
  • Tesla via CCS adapter has its own messages — note adapter brand/model

Decision tree

Capture first: brand/model of EV + adapter if any, EVSE firmware, connector (CCS1 vs CCS2), outdoor temp, whether AC Level 2 works on same site (if dual).

Branch 1 — No lock / no CP activity

  1. Measure PP resistance at inlet path if accessible (typical approx values vary by current capability — compare to OEM table, not memory).
  2. Inspect latch, debris, ice, bent proximity pin.
  3. Try second cable/gun if dual.
  4. If PP open/short → cable/handle; if PP good and no CP PWM → EVSE control board / CP driver.

Branch 2 — Lock OK, fails in under ~5 s (SLAC/SDP region)

  1. Clean contacts; reseat firmly; avoid partial insert.
  2. Known-good EV test.
  3. If only one EV model fails → vehicle/adapter; if all fail → PLC modem, PE quality, noisy site, firmware.
  4. Check PE continuity and bonding; poor PE wrecks PLC.

Branch 3 — Reaches CableCheck, fails isolation

  1. Treat as safety — do not hammer retries.
  2. Dry cable; inspect jacket; check for flood debris in handle.
  3. If dry and persistent: IMD/cable insulation/contactor path — escalate with OEM code.
  4. Confirm site was not pressure-washed into the inlet.

Branch 4 — CableCheck OK, PreCharge fails / timeout

  1. Note whether EVSE reports EV voltage mismatch or EVSE bus never rises.
  2. PreCharge timeout with healthy second EV → EVSE power stage / precharge resistor path.
  3. Only one EV fails → vehicle HV contactors / EV precharge — still document, do not argue with drivers in the rain.

Branch 5 — CurrentDemand starts, then abort

  1. Look at kW vs time: immediate abort vs thermal ramp.
  2. Immediate: EV max mismatch, emergency shutdown, lost PLC (PE intermittent).
  3. Ramp then abort: cooling, grid undervoltage, LMS cut, connector overtemp.
  4. Correlate with SuspendedEVSE vs Faulted in OCPP.

Branch 6 — Intermittent only when wet / hot / after long idle

  1. Wet → seals and drainage.
  2. Hot → derate and liquid loop (see cooling guide).
  3. Long idle → sticky lock or modem watchdog; check uptime.

Ranked causes with field notes

  1. Partial insert / dirty CCS pins / bent PE — Still #1 on public sites. Field note: wipe with approved contact cleaner; never sandpaper plating off.
  2. Adapter stack (NACS↔CCS, etc.) — Extra junctions, extra thermals. Field note: test native CCS EV before condemning EVSE.
  3. PE / earth quality killing PLC — SLAC flaky on multiple vehicles. Field note: check ground rod bonding and loose PE lugs under LOTO.
  4. CableCheck isolation trip — Moisture or damaged cable. Field note: one gentle retry after dry; then quarantine cable.
  5. PreCharge / bus voltage mismatch — Power module or EV. Field note: second EV is the cheap oscilloscope.
  6. PLC modem / firmware — Cluster failures after update. Field note: compare firmware train across site.
  7. CP PWM driver / control pilot hardware — No session any car. Field note: CP open-circuit voltage / PWM % per OEM service (LOTO if probing inside).
  8. Lock actuator intermittent — Mechanical. Field note: listen; service-menu lock cycle.
  9. LMS / site voltage sag during CurrentDemand — Looks like handshake abort. Field note: log Vac under load.
  10. Vehicle OEM bug — Real. Field note: document VIN/model/year; do not “fix” by yelling at CSMS.

Step procedures

Procedure A — Presentation pack

Tools: phone, CSMS.

  1. Video the plug attempt from ready to error (10–30 s).
  2. Export session timeline.
  3. Note ambient temp and whether cable was on the holder or lying in a puddle. Expected: Clear stage of death (lock, SLAC, CableCheck, PreCharge, CurrentDemand).

Procedure B — PP/CP sanity at the handle (de-energized checks first)

Tools: DMM, OEM breakout if issued.

  1. Unplug EV. Inspect pins: PE, PP, CP, DC+, DC−, tempsense if present.
  2. PP resistance vs OEM table for that cable rating.
  3. If OEM allows CP measurement during Preparing: compare PWM duty to expected state — only with rated PPE and procedure. Expected: PP in range; pins straight; no green crust bridging PE to signal.

Procedure C — Dual vehicle / dual gun matrix

  1. EV-A on Gun1, EV-B on Gun1, EV-A on Gun2.
  2. Fill a 2×2 result grid in the ticket. Expected: Pattern isolates gun vs vehicle vs site.

Procedure D — Isolation failure response

  1. Stop retries.
  2. Quarantine cable if portable; red-tag gun if attached.
  3. LOTO before any insulation test inside cabinet.
  4. Escalate with humidity + photos. Expected: No further CableCheck spam that stresses contactors.

Procedure E — PreCharge / CurrentDemand with metering

Tools: CSMS MeterValues, clamp if safe/authorized on AC side only unless OEM DC procedure exists.

  1. Watch Vac at cabinet under the failed attempt.
  2. Watch whether DC voltage appears in MeterValues.
  3. If Vac sags hard at CurrentDemand → power quality path, not PLC. Expected: Distinguish protocol abort from site power collapse.

Procedure F — Firmware / PLC hygiene

  1. Confirm EVSE time is correct (TLS and logs).
  2. Note PLC-related vendor codes.
  3. If OEM has “PLC reset” in service menu, use once and retest — not ten times. Expected: Stable SDP and CableCheck on known-good EV.

Safety / LOTO

  • DC+ / DC− can be lethal during and after failed PreCharge. Capacitors hold charge.
  • Do not defeat isolation monitoring to complete a handshake “for testing.”
  • Contact cleaner is flammable — no sparks, no smoking, dry fully before energizing.
  • Adapters can hide damage; inspect adapter shells for melt marks; melting means stop.
  • If the handle is hot enough to hurt, thermal fault — cooling / derate path, not more plug cycles.

CCS stage cheat-sheet (field memory)

StageWhat you want to seeTypical fail signature
Plug + PPLock path readyNo lock / PP fault
CPPWM in expected stateNo PWM / stuck 12 V
SLACPLC linkInstant fail both cars → PE/modem
SDPPort / security setupFail one OEM EV → EV/ISO stack
Fine alignment / authContract or EIMPayment/PnC — see those guides
CableCheckIsolation OKIMD / wet cable
PreChargeVoltages convergeTimeout / mismatch
CurrentDemandAmps riseAbort / derate / grid

Exact state names differ by DIN vs ISO 15118; use OEM language in tickets.

When to escalate

OEM: isolation trips dry cable; PreCharge never builds bus on two EVs; PLC modem suspect after PE verified; burnt DC pins.

Vehicle OEM / fleet: single model/VIN family fails everywhere.

Electrician: PE open, lost neutral/phase, Vac collapse under load.

Network/CSMS: only if auth/PnC is the stage — handshake PLC itself is local.

Do not escalate “CCS broken” without the stage of death and a second-vehicle result. That is how tickets bounce.

Field worksheet

CheckResult
CCS1 or CCS2
Adapter used
Stage of death
Gun number
EV #1 result
EV #2 result
PP inspection
PE spot-check
Vac under attempt
vendorErrorCode
Cable quarantined

Noise, PE, and “it works at the other plaza”

PLC (HomePlug Green PHY class behavior on CP/PE) hates:

  • Loose PE lugs
  • Shared noisy motors on the same ground without discipline
  • Corroded PE in the handle
  • Some poorly shielded add-on meters or radios inside the cabinet (rare but real after “upgrades”)

If SLAC fails at Site A and works at Site B with the same EV and similar firmware, prioritize earth and handle PE before ordering a power module.

Auth vs handshake (do not confuse)

  • RFID timeout during Preparing can abort before CableCheck — that is payment stack.
  • FreeVend or PnC test separates “won’t talk PLC” from “won’t authorize.”
  • ISO 15118 PnC failures after SDP are not SLAC failures — see the PnC guide.

Closeout

Leave the gun Available only if known-good EV completed CurrentDemand ≥1 minute or you red-tagged a specific cable/gun with site approval. Write the stage of death in the first line of the ticket closeout. EOF

Extended field scenarios

Scenario: Works with truck, fails with passenger EV

High-clearance trucks sometimes seat the connector more fully. Passenger cars with bumper shrouds get partial insert. Before condemning PLC:

  1. Have the driver remove inlet caps fully.
  2. Push until lock clicks; do not rely on “it feels in.”
  3. Check for aftermarket license-plate brackets hitting the handle.
  4. Retest. If still model-specific, document bumper geometry in the ticket.

Scenario: First attempt fails, second works

Often moisture film or incomplete latch. Still capture the first failure code — intermittent SLAC under humidity predicts afternoon callbacks. If the site is coastal, schedule contact inspections.

Scenario: CableCheck fails only after rain

Drainage path into the handle is clogged. Blow out (carefully, approved methods), check seals, holster drain holes. Quarantine if water drips from the handle when tilted.

Scenario: PreCharge timeout after power module swap

Installer left DC sense wiring loose or busbars unevenly torqued. LOTO, verify torque paint marks, confirm OEM torque values. PreCharge is a ruthless inspector of assembly quality.

Scenario: CurrentDemand aborts at exactly the LMS cap

Not a handshake bug. CSMS will show SuspendedEVSE or flat MeterValues at the cap. Check LMS before ordering PLC modems.

Tools kit for CCS calls

ToolUse
Phone videoStage of death
Flashlight / borescopePins and PE
True-RMS DMMPP, Vac (authorized points)
Contact cleaner (approved)Film on pins
IR thermometerHandle heat vs ambient
Known-good EV accessMatrix
CSMS exportCodes + MeterValues
Dielectric gloves / PPEAny energized work
LOTO kitCabinet entry

If you lack a known-good EV, say so — your isolation of “EVSE vs vehicle” is incomplete.

Documentation quality bar

A good CCS ticket first line: Gun2 CableCheck fail both EVs; PE lug OK; Vac 480 stable; vendor=ISO_CABCHK_47; cable red-tagged

A bad first line: CCS not working

Interaction with liquid cooling

Cooled CCS cables that airlock will abort in CurrentDemand with thermal codes that drivers describe as “handshake failed.” Always ask whether power ever rose above 0 kW. If yes for even 10 seconds, you left pure SLAC land.

Interaction with payment

Authorize timeout during Preparing cancels before CableCheck. FreeVend or tech RFID once. If FreeVend reaches CableCheck and paid path does not, switch guides.

Night work notes

PLC debugging under temporary lights is fine; probing CP inside the cabinet at night without a second qualified person is how mistakes happen. Prefer morning module for HV procedures.

Seasonal patterns

  • Winter: stiff seals, ice in latch, false PP.
  • Summer: thermal aborts mislabeled as protocol.
  • Pollen season: insulating film on pins in some regions — clean and retest.

Closeout expanded checklist

  • Stage of death named
  • Two-EV matrix or explicit gap stated
  • PE/pin inspection photos
  • Vac under attempt recorded if power stage reached
  • Cable quarantine status
  • Related Directory searches checked
  • Escalate target named if unresolved

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