P28BB

Code

Generic P — Powertrain

Cylinder 11 Ion Current Sense Circuit High

Brand: Generic

Type: P — Powertrain

Views: UK: 13 EN: 26 RU: 23

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Short to battery voltage in cylinder 11 ion sense wiring or connector
Corroded/contaminated coil, spark plug, or well creating unwanted conductive path
Damaged or chafed harness causing intermittent/high voltage readings
Faulty ignition coil or coil pack with internal sensor failure
Poor or missing ground at coil/engine harness or ECU ground
Faulty ECU/PCM ion sensing input (less common)

Read freeze frame and live data to confirm when code set (engine temp, rpm, throttle)
Inspect coil, spark plug, and well for oil, corrosion, or carbon tracking on cylinder 11
Visually inspect wiring and connector for cylinder 11 ion sense for damage, corrosion, bent pins, or water intrusion
Check engine and harness grounds for tightness and corrosion
Compare live ion‑current signal (or related live data value) for cylinder 11 versus another cylinder using scan tool
Scan for related misfire or ignition coil codes

Normal: brief ion‑current pulses correlated with combustion events on the coil/plug; amplitude is low and returns to baseline between events
High/Failed condition: sustained elevated voltage/current on cylinder 11 input or pulses above ECU threshold causing the DTC
Compare cylinder 11 signal shape and baseline to a known good cylinder — excessive DC offset, noisy or continuously elevated value indicates a problem

Record freeze frame and live data; note conditions when code set (rpm, temp, load).
Visually inspect coil 11, spark plug and well for contamination, oil, carbon, or damage; replace plug if fouled.
Inspect connector and wiring for cylinder 11 ion sense — look for corrosion, bent pins, melted insulation, or signs of short to battery. Repair any damage.
Check ground(s) related to the coil/ignition harness and engine block; clean and tighten as needed.
With ignition off, measure resistance/continuity between ion sense pin at the coil connector and the ECU pin (refer to OEM pinout). Verify no short to battery (+B) and no short to ground unless expected by design. Repair as needed.
Backprobe the coil ion sense pin with engine cranking/running and compare waveform/voltage to a known good cylinder using an oscilloscope or advanced scan tool. Look for elevated DC level or continuous voltage.
Swap the coil (and associated harness connector if possible) from cylinder 11 with a known good cylinder to see if the code follows the coil or remains on cylinder 11. If it follows, replace the coil. If it remains on cylinder 11, focus on wiring/connectors/ECU input.
If wiring checks good and problem follows to ECU input, consult manufacturer service data and consider ECU input testing or replacement per shop procedures.
After repairs, clear codes and road test under the same conditions to verify the fault does not return.