P2303: Ignition Coil B Primary Control Circuit Low
Do not keep driving
Stop if the engine light is flashing. Ask which cylinder this coil actually serves on your engine rather than assuming it is number two — the lettering follows the manufacturer's scheme past coil A, and on some engines reaching the wrong cylinder means dismantling the inlet manifold for nothing.
What this code means
Coil B's primary control circuit reads below its valid range. The primary and secondary distinction is at P2300, and the swap test at P0351.
One caution belongs with the second coil in the sequence: the letters are not a reliable guide to cylinder numbering. Coil A is cylinder 1 on almost every engine, but from B onwards the mapping follows the manufacturer's own scheme — which may run along the block, alternate between banks on a V engine, or follow firing order. Do not assume coil B is cylinder 2 without checking the firing order for the engine. Pulling the wrong plug is a wasted hour on some engines and a considerably worse one where the inlet manifold has to come off to reach it.
Likely causes
Start here
- Faulty ignition coil · easy
- Wiring shorted to ground · moderate
- Damaged wiring harness · moderate
Less common
- Corroded or loose connector · easy
- Faulty ignition coil driver in the module · specialist
Symptoms
Components involved
Information, not instruction
CarGeek is a reference, not a service manual. Its pages are written from public sources and from what other people have found, never from a manufacturer's own service information, so they can be wrong or incomplete for your particular vehicle. Some of what they describe carries real risk: high voltage, fuel under pressure, stored energy, hot and moving parts.
Have anything you intend to act on checked by a trained person against the manufacturer's own procedure for your vehicle. Nothing here replaces that procedure.
Community experience
Be the first to write this up
Nothing posted about this yet. Whatever you found is worth writing down — even a dead end saves someone the same afternoon.
What makes one worth reading:
- The car — make, model, year and engine. The same fault behaves differently on each.
- What you measured, not only what you replaced.
- What actually fixed it — or that nothing did, which is worth knowing too.
Sign in or create an account to add what you found about P2303.