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No Charging Diagnosis

5 boards 22 diagnostic checks Updated March 15, 2026

Overview

A MacBook that does not charge may still power on from battery. The diagnosis differs significantly between USB-C charging (CD3215/CD3217 USB-C controllers + ISL9239C charger) and MagSafe 1/2 (ISL6259 charger with direct barrel input). Key diagnostic signal: SMC_BC_ACOK — the adapter-OK signal from the charger IC to the SMC. If SMC_BC_ACOK is absent with a known-good adapter, the charger IC is not detecting or is not negotiating the adapter. Start there.

Diagnostic Methodology

Follow these steps in sequence. Each step eliminates an entire fault zone — do not skip ahead.

1. Test with known-good cable + adapter
Before touching the board, test with a known-good Apple USB-C cable and OEM charger on each port. Third-party cables often fail CC negotiation silently.
2. Check SMC_BC_ACOK
This signal must be 3.3 V when a valid adapter is connected. Absent SMC_BC_ACOK = charger IC not reporting adapter presence to SMC.
3. Measure VBUS at USB-C port
VBUS on USB-C port pin A4/B4 should be 5 V standby from adapter. If absent: USB-C controller or board-side ESD/TVS diode failure.
4. Check CC communication
CC1/CC2 lines carry USB-PD negotiation. Short or broken CC line prevents power delivery handshake. Measure CC resistance to GND — should be ~5.1 kΩ pulldown on device side.
5. MagSafe: check connector pins
MagSafe 1/2: inspect all 5 pins for corrosion and bent contacts. Pin 1 and 5 are ground, pin 3 is center power, pins 2/4 are ID/data. Clean with IPA.
6. Charger IC output
If VBUS and CC are fine but no charging: charger IC (ISL9239C / ISL6259) not converting input to PPBUS. Measure output and enable signals.

Per-Board Fault Trees

Board-specific checks ordered by failure likelihood. Most common root cause listed first.

MacBook Air A2337 (M1) — USB-C Charging Start: VBUS at USB-C port → T6022 BMIC
⊞ Repair guide ◈ Schematic hub
  • No charging on both ports
    T6022 BMIC not receiving VBUS or CC. Check both CD3215 USB-C controllers. Verify PPBUS_G3H from battery — if battery depleted, confirm with bench power supply injection.
  • No charging on one port only
    CD3215 on that port. Measure VBUS at port pins. Check VCONN enable. Inspect port physically for bent pins or corrosion (IPA clean first).
  • Charges intermittently
    CD3215 VBUS negotiation instability. Check board-side capacitors on CC lines. Re-solder CD3215 or replace — very common on A2337.
  • Charges with OEM cable, not third-party
    CC pull-down resistor value or CD3215 USB-PD profile. This is expected with non-certified cables. Not a board fault.
  • Battery not detected
    Battery BMS communication — separate from charging fault. Check battery connector and SMBus lines from T6022 to battery.
MacBook Pro A1989 (Touch Bar) — USB-C Charging Start: VBUS → CD3217 → ISL9239C → PPBUS_G3H
⊞ Repair guide ◈ Schematic hub
  • SMC_BC_ACOK absent
    ISL9239C not detecting adapter. Check D6900 TVS diode on VBUS (often fails after surge). Measure VBUS directly at ISL9239C input. Also check F6900 fuse continuity.
  • No charging left-side ports only
    Left-side CD3217 controller. Very common failure site on A1989 after liquid ingress near keyboard. Replace CD3217 on left cluster.
  • No charging right-side ports only
    Right-side CD3217 controller. Inspect right port area for liquid damage indicators.
  • Charges, then stops at X%
    Battery BMS or cycle count. Verify SMBus communication from ISL9239C to battery. Check battery health — may need replacement.
  • No charging after USB-C repair
    Re-check CD3217 solder joints (QFN package — reflow carefully). Verify CC lines not shorted to VBUS or GND after work.
MacBook Air A2681 (M2) — USB-C + MagSafe 3 Start: MagSafe 3 or USB-C VBUS → T6002 BMIC
⊞ Repair guide ◈ Schematic hub
  • No charging via MagSafe 3
    MagSafe 3 port routes to T6002 through dedicated path. Inspect MagSafe connector for corrosion on pins. Check board-side MagSafe connector pads.
  • No charging via USB-C (both ports)
    T6002 BMIC issue or upstream VBUS fault. Check CD3215 on both ports. Verify PPBUS_G3H from battery to confirm battery is not fully depleted.
  • No charging via USB-C (one port)
    CD3215 on that port. Same diagnosis as A2337. Replace CD3215 for affected port.
  • MagSafe LED amber, won't go green
    Battery BMS not acknowledging full charge. Check SMBus battery communication. May be genuine battery degradation.
  • No MagSafe LED at all
    MagSafe connector or T6002 not asserting power. Check continuity of MagSafe cable and connector pins.
MacBook Pro A1278 — MagSafe 2 Start: MagSafe DC-in → ISL6259 → PPBUS_G3H
  • No LED on MagSafe connector
    ISL6259 not asserting ADAPTER_SENSE. Check DC-in board connector continuity. Inspect MagSafe port for corrosion or bent center pin.
  • SMC_BC_ACOK absent
    ISL6259 not detecting or outputting adapter-OK. Measure VADP directly at ISL6259 input. If VADP present but ACOK absent: ISL6259 fault.
  • Charges on AC, not on battery
    Battery path through ISL6259 — check battery MOSFET (Q7030 area). Verify battery voltage and pack connector health.
  • LED green but not charging
    SMC_BC_ACOK asserted but SMC not enabling charge current. Likely a software/SMC issue — try SMC reset. If persists: SMC crystal or firmware fault.
MacBook Pro 820-01949 (A2141) — USB-C Charging Start: VBUS → CD3217 × 4 → ISL9239C → PPBUS_G3H
⊞ Repair guide ◈ Schematic hub
  • No charging via any of 4 ports
    ISL9239C charger output fault or SMC not enabling charge. Verify PPBUS_G3H from battery. Check SMC_BC_ACOK with all 4 CD3217 controllers.
  • No charging via 1–2 ports
    CD3217 on affected port(s). A2141 has 4 USB-C ports — 2 per side. Identify which side fails. Common after liquid spill on left/right keyboard area.
  • Charges slowly (5W instead of 96W)
    USB-PD negotiation failing — CD3217 falling back to 5V/0.9A. Check CC lines. May also be failing cable or adapter.

Frequently Asked Questions

What is SMC_BC_ACOK and why does it matter?
SMC_BC_ACOK (Battery Controller / Adapter Connected OK) is a 3.3 V logic signal generated by the charger IC (ISL6259 or ISL9239C) to tell the System Management Controller that a valid power adapter is connected. Without this signal, the SMC will not enable charging — even if voltage is physically present on the board. It is the most important single signal to verify in any no-charging diagnosis on Apple boards.
Why does the Mac charge with an Apple cable but not third-party?
Apple USB-C chargers use USB Power Delivery (USB-PD) negotiated over CC lines. The CD3215/CD3217 USB-C controller handles this negotiation. Third-party cables with poor CC resistors, damaged CC pins, or non-compliant PD profiles may not trigger the handshake. This is usually not a board fault — test with an OEM Apple USB-C cable and 61W+ charger to confirm.
The port charges if I hold the cable at an angle. What does this mean?
This indicates a broken USB-C port connector on the board, or a damaged cable. The USB-C port pins are making intermittent contact. This is a physical/mechanical fault — the port needs to be replaced via microsoldering. Do not continue using the machine in this state as it risks further connector pad damage.