P2890

Code

Generic P — Powertrain

Cylinder 1 Ion Current Sense Circuit

Brand: Generic

Type: P — Powertrain

Views: UK: 25 EN: 25 RU: 19

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Causes

Open or short in the ion-current wiring for cylinder 1
Poor or corroded connector at ignition coil, plug or harness
Faulty ignition coil or coil pack for cylinder 1
Damaged or incorrect spark plug for cylinder 1 (insulation issues)
High resistance or poor ground in ignition/engine grounds
ECM or ignition control module fault

Symptoms

Malfunction Indicator Lamp (MIL) illuminated
Possible misfire or rough idle on cylinder 1
Reduced engine performance or hesitations under load
Poor fuel economy
Intermittent starting or stumbling
Inconsistent knock/no-knock behavior or unexpected timing adjustments

What to check

Read freeze frame and related codes with a scan tool; record live data for ion-current or knock/combustion-sensing channels
Visual inspection of ignition coil, spark plug, wiring harness, and connectors for damage or contamination
Check for additional DTCs: misfire (P0301), ignition coil primary/secondary (P0351), ECM faults
Wiggle test harness and connectors while monitoring live data or checking for MIL change
Measure continuity and resistance of ion circuit wiring to the ECM and to ground
Swap cylinder 1 coil with another cylinder to see if the code follows the coil

Signal parameters

Ion-current pulse should be timed with the ignition event (crank angle related) and show a transient AC pulse corresponding to combustion
Expected waveform: short-duration pulse(s) at the time of ignition; steady flatline indicates open/no signal
Low or no pulse amplitude suggests open circuit or failed coil; excessive DC offset or constant high level suggests short to voltage
Signal amplitude typically in microamp to low milliamp range (system-dependent); noise or irregular spikes indicate wiring or grounding problems
Presence/absence of expected pulses when comparing cylinder 1 to other cylinders is a key diagnostic parameter

Diagnostic algorithm

Verify code: Retrieve P2890 and any related/history codes. Note freeze-frame data and attempt to re-create the symptom with clear/drive cycle.
Visual inspection: Check ignition coil, plug, connector, and wiring for damage, corrosion, oil, or coolant contamination. Repair as needed.
Connector/ground checks: Disconnect battery ground if required for safety, then inspect and clean connector pins and engine/ignition grounds. Reconnect and recheck.
Wiggle and scan: With scan tool monitoring ion-current channel or related live data, wiggle connectors and harness to spot intermittent faults.
Swap components: Swap the cylinder 1 coil (and associated plug if practical) with another cylinder. If code moves to the other cylinder, replace the coil/plug assembly.
Electrical tests: Check continuity and resistance of the ion-current wiring from the coil to the ECM connector. Look for short to battery or ground. Repair any open/shorts.
Scope test: Use an oscilloscope to view ion-current waveform on cylinder 1 and compare to a known-good cylinder. Look for missing pulses, excessive noise, or DC offset.
Check spark and compression: Confirm spark quality and perform a compression/leakdown test if mechanical issues are suspected that could affect ion signal.
Replace suspect parts: Replace faulty coil, spark plug, or harness as indicated by tests. Use OEM or ion-sensing-compatible ignition components.
ECM check: If wiring and components are confirmed good and the fault persists, evaluate ECM/ignition control module for internal fault; consult manufacturer's procedures for reprogramming or replacement.
Verify repair: Clear codes and perform a drive cycle or test conditions to ensure P2890 does not return.