P2894

Code

Generic P — Powertrain

Cylinder 2 Ion Current Sense Circuit

Brand: Generic

Type: P — Powertrain

Views: UK: 20 EN: 31 RU: 19

AI status

Completed

ready

Completed 100%

Page language: EN

Causes

Open or short in ion current sense wiring or connector for cylinder 2
Corroded/loose connector or poor ground at coil/ECM
Faulty ignition coil or spark plug (cylinder 2)
Contaminated or damaged coil-on-plug boot or electrode
Intermittent wiring damage from rubbing/heat
Faulty ECM/ignition module sensing circuit

Symptoms

Malfunction Indicator Lamp (MIL) illuminated
Possible misfire on cylinder 2 (rough idle, hesitation)
Reduced engine power or drivability complaints
Decreased fuel economy and increased emissions
Engine may run normally at times if issue is intermittent

What to check

Read and record freeze-frame and stored codes; note any misfire codes (e.g., P0302)
Visually inspect coil-on-plug, spark plug, boot and harness for damage, corrosion or oil contamination
Inspect and wiggle-wire test ion-sense wiring and connectors while monitoring scan data or oscilloscope for change
Check for other related DTCs (ignition coil, misfire, ECM communication)
Measure coil primary and secondary resistance per manufacturer spec
Back-probe ECM ion-sense pin to observe waveform or use an oscilloscope/current probe on the ion-sense return path

Signal parameters

Ion current is a microamp-range signal (commonly reported as ~0–1000 µA depending on engine/ECU) — expected transient spikes synchronized to ignition/combustion events
Ion-sense is usually measured as a small current or corresponding small voltage across the ECM’s sense resistor (tens to hundreds of millivolts) rather than a battery-voltage DC level
Expected waveform: short-duration spike shortly after ignition event; amplitude and shape vary with load and rpm
Typical ignition coil primary resistance (for reference) often ~0.3–2 Ω; secondary resistance often in the kΩ range (consult vehicle spec)
Continuity: wiring between coil sense pin and ECM should show low resistance and no intermittent opens (continuity < a few ohms for short runs)

Diagnostic algorithm

Connect a scan tool; record freeze frame and live data. Note any concurrent misfire codes (P0302) or coil codes (P0352).
Perform a visual inspection of cylinder 2 coil-on-plug, spark plug, boot and harness; repair any obvious damage or contamination.
Perform a wiggle test on the ion-sense wiring and connector while observing scan data or oscilloscope for signal changes.
Check coil electrical values: measure primary and secondary resistance and compare to specification. Replace coil or plug if out of range or visibly damaged.
Back-probe the ECM ion-sense terminal (or the coil sense terminal) and capture the ion-current waveform with an oscilloscope or current probe. Verify there are combustion-synchronized spikes for cylinder 2 similar to other cylinders.
If waveform or current is absent, check continuity and resistance between the coil sense terminal and ECM pin; repair any opens/shorts and poor grounds.
Swap coil (and plug if practical) between cylinder 2 and a known-good cylinder. If the code follows the coil or plug, replace the failed component.
After repairs, clear codes and perform a road test under varying loads and RPMs to confirm the issue is resolved.
If wiring and components check good and problem persists, consider ECM/ignition-module fault. Verify power/ground/communication at ECM before ECM replacement.

Likely causes

Broken/shorted harness between cylinder 2 coil and ECM
Failed ignition coil (cylinder 2) or degraded secondary winding
Damaged spark plug or electrode preventing reliable ion signal
Corroded connector or poor ground at coil/ECM pin
Intermittent open/short that appears under vibration or thermal change

Fault status

⚠️ Status

DTC P2894 — Cylinder 2 Ion Current Sense Circuit. The ECM detected an abnormal or missing ion-current signal from cylinder 2 (open/short/intermittent or out-of-range). Inspect wiring, coil/spark plug, connectors and ECM sensing circuit.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 1.0-2.5 hours