P28B2

Code

Generic P — Powertrain

Cylinder 9 Ion Current Sense Circuit Low

Brand: Generic

Type: P — Powertrain

Views: UK: 27 EN: 36 RU: 24

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Page language: EN

Open or high‑resistance wiring between coil/ignition module and ECM ion sense input
Corroded/loose connector at coil, spark plug, or ECM
Faulty ignition coil or coil driver for cylinder 9
Damaged or fouled spark plug, worn electrode or wrong gap
No combustion in cylinder 9 (fuel, compression, or timing issue)
Faulty fuel injector or lack of fuel to cylinder 9

Read freeze frame and live data for ion sense channel and misfire counters
Compare ion signal for cylinder 9 to other cylinders using oscilloscope or OEM scan tool
Visual inspection of ignition coil, spark plug, wiring harness and connectors for cylinder 9
Check connector pins for corrosion, bent pins or poor mating at coil and ECM
Confirm spark at plug (use safe in‑cylinder method or scope)
Measure continuity and resistance of ion sense wiring and shield to ECM

Expected: short ionization pulse synchronized with ignition event shortly after spark; amplitude typically in the microamp to low milliamp range depending on system and engine design
Low condition: ion pulse amplitude near 0 µA or below ECM threshold for detection
Timing: pulse should occur within the ignition event window (milliseconds after coil discharge)
Waveform: bipolar or unipolar pulse depending on ignition topology; compare shape and amplitude to a known good cylinder

Retrieve code(s), freeze frame and live data. Note RPM, load, temperature and conditions when fault set.
Visually inspect cylinder 9 ignition coil, spark plug, wiring harness and connectors for damage, corrosion, loose connector or water ingress.
Using scan tool or oscilloscope, monitor ion sense waveform for cylinder 9 and compare to a known good cylinder while cranking and running. Confirm low or absent pulse.
Swap coil (or coil pack/module) and spark plug from a good cylinder into cylinder 9. Clear codes and run to see if fault follows the component.
Measure wiring continuity and resistance between coil ion sense terminal and ECM input. Check for shorts to ground or power and inspect shielding continuity.
Verify spark at plug and inspect plug condition (gap, fouling, electrode damage). Replace plug if suspect.
Check fuel injector for cylinder 9 operation (nozzle pulse, flow) and perform a balance test or use a stethoscope for clicking.
Perform a compression or leak‑down test on cylinder 9 to confirm combustion capability.
Inspect ECM power/ground and related fuses; check for software updates or TSBs that affect ion sensing logic.
If wiring, coil and plug verify OK and cylinder still shows low ion signal, consider ECM or ignition module replacement as last step. After repairs, clear codes and confirm normal operation on road test.