P28AA: Cylinder 7 Ion Current Sense Circuit Low

Ion current from cylinder 7 is below the expected window. Spark plug fouled, signal wire shorted to ground, or sensing path interrupted.

Cylinder 7 is numbered according to the manufacturer: check your engine's manual before working on it.

Most likely causes

• Spark plug fouled with carbon or oil
• Sense wire shorted to ground
• Connector pins corroded - high contact resistance

What to check, in order

Start with the simplest. You can tick off each step.

1. Check the battery, connectors, and wiring
2. With the connector unplugged, check whether the signal wire is making contact with ground.
3. Read the live data with a scanner
4. Follow the manufacturer's service manual

Good to know

• Repair difficulty: medium
• It affects emissions.

What each character of P28AA means

• P: Powertrain: engine and transmission
• 2: Generic code: same on every make
• 8: Transmission
• AA: Specific fault in that system

Frequently asked questions

Can I keep driving with code P28AA?

If the car is running normally, drive in moderation to a repair shop. If it loses power or another warning appears, do not continue.

What causes code P28AA?

The most common causes are: spark plug fouled with carbon or oil; sense wire shorted to ground; connector pins corroded - high contact resistance.

Related codes

• P28A6Cylinder 6 Ion Current Sense Circuit Low
• P28AECylinder 8 Ion Current Sense Circuit Low
• P28A2Cylinder 5 Ion Current Sense Circuit Low
• P28B2Cylinder 9 Ion Current Sense Circuit Low
• P289ECylinder 4 Ion Current Sense Circuit Low
• P28B6Cylinder 10 Ion Current Sense Circuit Low
• P289ACylinder 3 Ion Current Sense Circuit Low
• P28BACylinder 11 Ion Current Sense Circuit Low

Sources

• github.com: dtc database
• en.wikipedia.org: Ion current signal
• en.wikipedia.org: Ignition system

Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.