P289E

Code

Generic P — Powertrain

Cylinder 4 Ion Current Sense Circuit Low

Brand: Generic

Type: P — Powertrain

Views: UK: 20 EN: 24 RU: 21

AI status

Completed

ready

Completed 100%

Page language: EN

Causes

Open or shorted wiring in the cylinder 4 ion current harness (connector, broken wire, corrosion)
Poor connector contact or corrosion at coil pack / ignition module / ECU
Faulty ignition coil or ignition module with integrated ion sensing
Defective or fouled spark plug in cylinder 4
Fuel injector fault or lean/poor fuel delivery on cylinder 4
Mechanical issue on cylinder 4 (low compression, valve problem) reducing combustion ionization

Symptoms

Malfunction Indicator Lamp (MIL)/Check Engine Light illuminated
Possible rough idle or vibration if misfire occurs on cylinder 4
Intermittent or persistent misfire-related driveability issues
Reduced engine performance or hesitation under load
Misfire codes for cylinder 4 (P0304) may be present or recorded
Failed emissions test or high hydrocarbon (HC) readings

What to check

Read freeze-frame and live data for ion current channel and related misfire counters; note engine load, RPM, and temperature when fault set
Scan for related DTCs (P0304, P0300, knock sensor codes, injector codes)
Visually inspect wiring and connectors at cylinder 4 coil/ignition module and ECU for corrosion, damaged insulation, or loose pins
Swap coil pack/ignition module from cylinder 4 with another cylinder to see if code follows the coil
Inspect and measure spark plug condition and gap for cylinder 4; replace if fouled or damaged
Perform a spark test or secondary ignition verification if safe and applicable

Signal parameters

Expected: distinct ion-current pulse following ignition event with measurable peak amplitude relative to background noise
Low condition: pulse amplitude near noise floor or absent, flat or very low-magnitude waveform
Comparison: other cylinders should show consistent peak timing and amplitude under same operating conditions
Diagnostics: scope view typically uses microamp or mV-level signals depending on manufacturer-specific circuitry

Diagnostic algorithm

Retrieve DTC, freeze-frame, and related codes. Confirm P289E is current or stored.
Clear codes and attempt to reproduce under the same conditions. Note any intermittent behavior.
Visually inspect wiring and connectors for cylinder 4 ion sensing circuit (coil-to-ECU). Repair damaged wiring or connectors, then retest.
Swap the cylinder 4 ignition coil/ion-sensing module with a known-good cylinder. If the code follows the coil, replace the coil/module.
Inspect and, if necessary, replace the spark plug for cylinder 4. Re-test for the fault.
Use an oscilloscope or OEM scan-tool ion-current function to compare cylinder 4 waveform to a good cylinder. Look for absent or reduced peak.
If waveform shows normal ignition but no ion current, check fuel injector operation for cylinder 4 and perform a compression/leak-down test to rule out mechanical/compression issues.
If wiring, coil, plug, injector, and combustion are all good, test ECU input/output for the ion circuit and consider ECU repair or replacement as last resort.
After any repair, clear codes and verify the issue does not return during representative driving conditions.

Likely causes

Damaged or loose harness/connector at coil or ECU
Failed ignition coil or coil pack for cylinder 4
Bad or fouled spark plug in cylinder 4
Intermittent connector corrosion or water ingress
Combustion problem (misfire, low compression, or injector issue) specific to cylinder 4

Fault status

⚠️ Status

Cylinder 4 ion current sense circuit low — measured ionization signal below expected threshold (possible open/short, poor spark, or combustion issue).

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 1.0-3.0 hours