P28A8

Code

Generic P — Powertrain

Cylinder 7 Ion Current Sense Circuit

Brand: Generic

Type: P — Powertrain

Views: UK: 22 EN: 40 RU: 21

AI status

Completed

ready

Completed 100%

Page language: EN

Causes

Open, short to ground, or short to voltage in the Cylinder 7 ion-sense wiring or connector
Corroded, loose or damaged connector at the Cylinder 7 ignition coil
Faulty ignition coil with integrated ion-sensing circuitry
High resistance or poor ground at the coil or ECM connector
Contamination (oil/carbon) on coil boot or electrode preventing proper ion current
Faulty ECM/PCM or damaged ECM ion-sense driver circuit

Symptoms

Malfunction Indicator Lamp (MIL) illuminated
Rough idle or cylinder-specific misfire (may show as P0307)
Reduced engine performance and reduced fuel economy
Intermittent misfires or hesitation under load
Possible difficulty starting or unstable idle if ion sensing used for combustion control

What to check

Retrieve freeze frame and live data; confirm code and related misfire codes (e.g., P0307)
Visually inspect the Cylinder 7 coil, boot, and harness for damage, oil, carbon, or corrosion
Check connector pins for corrosion, bent pins, or poor mating
Swap Cylinder 7 coil with a known-good coil from another cylinder and see if the code follows the coil
Measure continuity and resistance of the ion-sense wiring between the coil connector and the ECM pin
Check power supply and ground at the coil harness connector with ignition on

Signal parameters

Ion-sense signal is an ignition-synchronized waveform present immediately after the spark event; expected: a repeatable pulse pattern for a healthy combustion event
Open-circuit condition: no ion-sense pulses detected from the cylinder during its ignition event
Short-to-ground: flattened or very low amplitude signal (near 0 V) or constant low reading
Short-to-battery: abnormally high or clamped voltage level; may show constant/high reading or saturated output
Healthy vs faulty comparison: amplitude, timing relative to spark, and repeatability across cycles are the key distinguishing parameters

Diagnostic algorithm

Verify DTC: Connect a capable scan tool, record freeze frame, and check for additional codes (P0307, ignition coil codes, ECM faults).
Visual inspection: With ignition off, inspect Coil 7, boot, harness, and connector for damage, oil, carbon, or corrosion. Repair any obvious damage.
Clear codes and attempt to reproduce: Clear DTCs, start engine, and see if the code returns or if misfire appears.
Swap test: Swap Coil 7 with a coil from another cylinder. If the code moves to the other cylinder number, replace the coil.
Electrical checks: With connector disconnected, check for proper reference voltage/power and ground at the coil connector. Verify continuity between coil ion-sense pin and ECM pin; check for shorts to ground/voltage.
Signal capture: Use an oscilloscope or manufacturer bi-directional scan-tool to capture ion-current waveform on Cylinder 7 and compare to a known-good cylinder while cranking/idle. Look for missing, shifted, or low-amplitude pulses.
Inspect/clean coil boot and spark plug: Replace spark plug and ensure boot is clean and free of oil/carbon. Re-test.
Repair harness/connectors: Repair broken wiring, corroded pins, or poor grounds. Use proper crimping, sealing, and heat-shrink where needed.
ECM check: If wiring and coil are verified good and problem persists, test or replace the ECM only after verifying with manufacturer procedures.
Final test: Clear codes, perform road test and verify code does not return and that misfires (if present) are resolved.

Likely causes

Damaged or corroded connector/wiring to the Cylinder 7 coil (most common)
Faulty ignition coil with integrated ion-sensing function
Poor ground or supply to coil harness affecting the ion-sense circuit
Contamination on coil boot causing weak/no ion signal
Less likely: ECM driver fault

Fault status

⚠️ Status

PCM detected an abnormal or missing ion-current sensing signal for Cylinder 7. The fault indicates the ion-sense circuit produced no valid combustion-related waveform or an out-of-range signal (open, short, low amplitude, or timing error). The condition may be active, pending or stored in history.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 1.0-2.5 hours