P2303
Ignition Coil "B" Primary Control Circuit Low
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The P2303 code means the PCM has detected that the voltage in the primary control circuit for ignition coil B is lower than the expected range. This is essentially the same type of problem as P2300 but for a different coil — coil B instead of coil A. The primary circuit is what the PCM uses to control the timing and firing of the ignition coil.
When ignition coil B is not receiving proper voltage, the associated cylinder or cylinders will misfire. You will notice rough running, especially at idle, and a definite loss of power. The engine may vibrate noticeably and fuel economy will drop. If the misfire is severe enough, the engine may stall at low RPM.
Diagnosis should start with a visual inspection of the wiring harness and connectors for coil B. Look for obvious damage like frayed wires, corrosion on connector pins, or evidence of animal chewing. If the wiring looks good, replacing the ignition coil is typically the fix. Coil replacement is usually a bolt-on job that takes less than 30 minutes on most vehicles. If the problem persists, the ignition control module or PCM may require professional diagnosis.
Severity
Symptoms
- •Check Engine Light is on
- •Engine misfires on one or more cylinders
- •Rough idle or engine vibration
- •Loss of power during acceleration
- •Poor fuel economy
- •Engine may stall at low RPM
Likely Causes
The ignition coil for cylinder B has an internal failure causing the primary control circuit to read below normal voltage.
Broken, corroded, or chafed wiring between the PCM and coil B results in low voltage at the coil. Rodent damage is a frequent cause.
The module that drives the ignition coils may be failing, sending insufficient signal to coil B.
The PCM's internal coil driver for coil B may have failed, unable to supply proper voltage.
A corroded or loose ground for the ignition coil circuit can result in low voltage readings.
Estimated Cost
Professional Repair
Includes parts + labor
Common Fixes
- Replace ignition coil B
- Repair or replace damaged wiring and connectors
- Replace ignition control module
- Clean or repair ground connections