P0351 medium Severity

P0351: Ignition Coil 'A' Primary/Secondary Circuit Malfunction

May cause rough idle, engine misfire, power loss, difficulty starting and potentially catalytic converter damage if left unresolved

Overview

OBD‑II P0351 indicates a malfunction in the primary or secondary circuit of ignition coil A (cylinder #1), commonly due to coil failure, wiring/connector fault, or ECM control issue; causes misfire conditions.

Common Symptoms

  • Check engine light illuminated
  • Rough or erratic idle
  • Engine misfire, especially on cylinder #1
  • Poor acceleration and loss of power
  • Difficulty starting the engine

Most Common Causes

Faulty ignition coil 'A' (internal short/open) high

Most frequently observed trigger causing improper coil firing or electrical signal faults according to multiple references

Damaged or corroded wiring/connectors in ignition coil circuit high

Open circuits, shorts to ground or voltage are common contributors to P0351

Faulty spark plug or plug wiring increasing coil load medium

Faulty secondary components can stress the coil circuit and trigger the code

PCM/ECM driver circuit malfunction low

Less common but possible, typically after wiring and coil faults have been ruled out

Diagnostic Steps

  1. Use an OBD‑II scanner to confirm P0351 and check for related misfire or ignition codes
    Expected: P0351 present with or without P0301 misfire codes
    Interpretation: Confirms ignition coil A circuit fault and helps correlate misfire presence
  2. Visually inspect ignition coil A, connectors, and wiring harness for damage, corrosion, or loose pins
    Expected: No visible damage or poor connections should be present
    Interpretation: Damage indicates likely cause; repair and test again
  3. Swap ignition coil A with another cylinder’s coil and re‑scan
    Expected: If code follows the coil to a new cylinder, coil is defective
    Interpretation: Confirms coil unit failure if the code changes to the other cylinder
  4. Test wiring continuity and resistance between PCM and coil primary circuit with multimeter
    Expected: Proper continuity within manufacturer spec
    Interpretation: Breaks or anomalies suggest wiring/connector fault
  5. Check spark plug condition and resistance; replace if fouled or outside spec
    Expected: Plugs within spec and properly firing
    Interpretation: Faulty plugs can mimic coil circuit faults and should be corrected

Repair Solutions

Replace faulty ignition coil A medium
Estimated Cost: $80 - $250

Cost varies by vehicle; OEM coils cost more than aftermarket

Repair or replace damaged wiring/connectors medium
Estimated Cost: $50 - $300

Depends on extent of wiring harness damage

Replace spark plug and plug wiring easy
Estimated Cost: $40 - $150

Recommended when secondary ignition components show wear

PCM/ECM repair or replacement hard
Estimated Cost: $500 - $3000

Consider only after eliminating other causes; relatively rare

Common Misdiagnoses

Avoid these common diagnostic mistakes:

  • Replacing ignition coils without diagnosing wiring faults
  • Assuming vacuum leaks are unrelated to ignition misfire symptoms
  • Replacing spark plugs without verifying circuit integrity

Frequently Asked Questions

What is the definition of the P0351 engine code?

Ignition Coil 'A' Primary/Secondary Circuit Malfunction is the standard definition for P0351. This diagnostic code is triggered when the ECU detects a problem in the Ignition.

Can P0351 cause engine damage?

The P0351 code is considered medium severity. May cause rough idle, engine misfire, power loss, difficulty starting and potentially catalytic converter damage if left unresolved

What happens when the P0351 code is active?

You may experience the following: Check engine light illuminated, Rough or erratic idle, Engine misfire, especially on cylinder #1.

Potential causes for OBDII code P0351

The most common causes are: Faulty ignition coil 'A' (internal short/open), Damaged or corroded wiring/connectors in ignition coil circuit, Faulty spark plug or plug wiring increasing coil load.

What is the price difference for fixing P0351?

The cost varies significantly based on the root cause. For example, replacing a Replace spark plug and plug wiring typically costs between $40 and $150, while fixing a PCM/ECM repair or replacement can range from $500 to $3000.

Is the P0351 code specific to Chevrolet?

The P0351 code is a generic powertrain code, meaning it applies to almost all makes and models, such as Honda, Toyota, VW, Ford, and Chevy.

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