P2899

Code

Generic P — Powertrain

Cylinder 3 Ion Current Sense Circuit Range/Performance

Brand: Generic

Type: P — Powertrain

Views: UK: 21 EN: 27 RU: 24

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Page language: EN

Causes

Open or short in ion-sense wiring or connector for cylinder 3
Corroded, loose or damaged connector at coil/spark plug/ECM
Failed ignition coil or coil pack with integrated ion-sensing
Failed ion-sensing module or sensor circuit in the ECM/ignition module
Bad or fouled spark plug, incorrect gap or damaged plug insulator
Poor compression or mechanical issue in cylinder 3 (valves, piston, head gasket)

Symptoms

Malfunction Indicator Lamp (MIL) illuminated and code P2899 present in history
Misfire on cylinder 3 or rough idle
Reduced engine power, hesitation or increased vibration under load
Increased fuel consumption or failed emissions test
Intermittent drivability problems correlated with engine speed/load

What to check

Read freeze frame and live data from ECM; note engine speed, load and conditions when code set
Perform a misfire cylinder balance or live misfire counts and compare cylinder 3 to others
Visually inspect wiring and connector for cylinder 3 ignition coil (pin damage, corrosion, chafing)
Inspect spark plug for wear, fouling, correct gap and proper installation
Confirm power and ground at ignition coil/ignition module and related fuses/relays
Swap ignition coil (or coil pack) between cylinder 3 and another cylinder to see if issue follows the coil

Signal parameters

Signal is synchronized with the ignition event for cylinder 3 (appears once per combustion event)
Waveform shows a combustion-related ion-current spike during/after spark; shape and amplitude should be similar to other cylinders under same conditions
Baseline should be near zero between events and not noisy or unstable
Signal should vary predictably with engine speed and load (higher engine load typically changes amplitude)
A flat, absent, inverted or erratic waveform indicates wiring/coil/sensor/combustion fault

Diagnostic algorithm

Connect scan tool, record freeze frame and live data. Confirm P2899 is active or stored; clear codes and road test to reproduce.
Compare ion-sense (or equivalent combustion detect) data and misfire counts across all cylinders; note if cylinder 3 differs.
Visually inspect coil 3 wiring, connector, and pin condition; repair any damage, ensure proper seating and corrosion-free contacts.
Inspect and remove spark plug 3: check gap, electrode condition, fouling or damage; replace with known-good plug if suspect.
Check coil power and ground circuits and relevant fuses/relays. Verify supply voltage and ground continuity at the coil.
Swap ignition coil (or coil pack) from cylinder 3 with an identical coil from another cylinder. Clear code and retest. If code follows the coil, replace the coil.
If swapping coil does not move the fault, inspect and test the ion-sense wiring back to the ECM for opens, shorts to ground or battery, and shielding integrity; repair wiring as needed.
Use an oscilloscope to capture the ion-sense or coil primary waveform on cylinder 3 and compare to a good cylinder. Look for missing spikes, reduced amplitude or abnormal noise.
If electrical components check good but ion signal remains abnormal, perform compression or leak-down test on cylinder 3 to rule out mechanical causes.
If injector or fuel delivery is suspected, test injector operation and fuel pressure; replace or repair as required.
If tests indicate the ECM or integrated ignition module is faulty, verify with manufacturer procedures before replacement (possible reprogramming or bench testing).
After repairs, clear codes and perform verification drive cycle to ensure the code does not return.

Likely causes

Damaged wiring or connector at cylinder 3 ignition coil
Failed ignition coil or ignition module that includes the ion sensing circuitry
Fouled or damaged spark plug in cylinder 3
Low compression or mechanical fault producing poor combustion and weak/no ion current

Fault status

⚠️ Status

ECM detected ion-current sense signal for cylinder 3 outside expected range or performance — abnormal or missing ion-sense waveform; may indicate ignition, wiring, sensor, or combustion problem on cylinder 3.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 1.5-3.5 hours