P28BB: Cylinder 11 Ion Current Sense Circuit High

Ion current from cylinder 11 is above the expected window. Cross-coupled signal, biased reference, or sensor fault.

Medium severity. Can I keep driving?If the car is running normally, drive in moderation to a repair shop. If it loses power or another warning appears, do not continue.

Cylinder 11 is numbered according to the manufacturer: check your engine's manual before working on it.

Most likely causes

Inductive cross-coupling from ignition coil primary
Sense reference voltage biased
Connector pins corroded - high contact resistance

What to check, in order

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

Check the battery, connectors, and wiring
Check the sensor's ground and make sure the signal wire is not receiving voltage from another circuit.
Read the live data with a scanner
Follow the manufacturer's service manual

Good to know

Repair difficulty: medium
It affects emissions.

What each character of P28BB means

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

Frequently asked questions

Can I keep driving with code P28BB?

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 P28BB?

The most common causes are: inductive cross-coupling from ignition coil primary; sense reference voltage biased; connector pins corroded - high contact resistance.

Related codes

Sources

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.