P2303

Ignition Coil B Primary Control Circuit Low

Ignition / misfire Generic OBD-II Medium

What it means

P2303 means the ECM has detected low voltage on the primary control circuit for ignition coil B — usually a short to ground or a failing coil. That cylinder can misfire, giving a rough idle and lost power, and a sustained misfire can damage the catalytic converter, so it should not be ignored.

Medium

Can I keep driving? Drivable but expect a misfire on that cylinder — if the check-engine light flashes, drive as little as possible to protect the catalytic converter.

Real-world scan data

Seen in

401

scans in the past year

Found in

0.1%

of scans

0.1%

of scans that found faults

Appears alongside · share of P2303 scans

P0352in 72.8% of scans

P2300in 42.9% of scans

P0351in 42.6% of scans

Figures reflect only diagnostic scans recorded through our own apps and tools. Cars are typically scanned because a symptom or warning light prompted it, so these counts describe our scan records — not the incidence of faults in any model, and not the quality, reliability, or safety of any vehicle. No comparison between manufacturers or models is implied. All trademarks belong to their respective owners; no affiliation or endorsement is implied.

Common symptoms

What you'll notice

Check-engine light on (may flash during an active misfire)
Rough idle, stumble, or hesitation
Loss of power on acceleration
Slightly increased fuel consumption

Common causes

Most likely first

Faulty ignition coil B or a short to ground in its primary windingLikely
Wiring shorted to ground on the coil control (driver) circuitCommon
Corroded or loose coil connectorCommon
Chafed harness near the coilLess often
Failed coil driver inside the ECM/ignition moduleLess often

How to diagnose & fix

Work through it in order

Read freeze-frame data and note which cylinder coil B feeds.
Inspect the coil connector and control wire for damage or a short to ground.
Swap coil B with a known-good coil and see if the fault follows the coil.
Check the control wire back to the ECM for a short.
Replace the coil if faulty, then clear and confirm the misfire is gone.

FAQ

Quick answers

Is it safe to drive with P2303?+

Only briefly. A steady misfire dumps raw fuel into the exhaust and can overheat the converter — a flashing light means stop driving soon.

Can I just clear P2303?+

It returns quickly because the ECM keeps monitoring the coil circuit until the coil or wiring is repaired.

Read & clear P2303 yourself

Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.

▶ Get it on Google Play

✓ Verified name — SAE J2012 / ISO 15031-6Guidance reviewed by OBD DashX