Introduction:

The diagnostic trouble code (DTC) P1351, often found in Ford, Lincoln, and Mercury vehicles, indicates a problem with the ignition coil control circuit. This code signals that the Powertrain Control Module (PCM) has detected a higher-than-expected voltage in the circuit controlling a specific ignition coil. Addressing this issue promptly is crucial to prevent engine misfires, reduced fuel efficiency, and potential damage to the catalytic converter.

Comprehensive Table: P1351 - Ignition Coil Control Circuit High Voltage

Category Detail Possible Causes
Basic Information Definition: Ignition Coil Control Circuit High Voltage. Indicates the PCM detected abnormally high voltage in the control circuit for a particular ignition coil. Affected Vehicles: Primarily Ford, Lincoln, and Mercury vehicles, but can appear in other makes. Severity: Can range from drivability issues to potential catalytic converter damage. Symptoms: Engine misfires, rough idling, reduced fuel economy, illuminated Check Engine Light (CEL), potential lack of power. Related Codes: P1350, P1352, P1353, P1354, P1355, P1356, P1357, P1358, P1359, P1360, P1361, P1362, P1363, P1364, P1365, P1366, P1367, P1368, P1369, P1370, P1371, P1372, P1373, P1374, P1375, P1376, P1377, P1378, P1379, P1380, P1381, P1382, P1383, P1384, P1385, P1386, P1387, P1388, P1389, P1390, P1391, P1392, P1393, P1394, P1395, P1396, P1397, P1398, P1399, P1400. Faulty Ignition Coil: A coil with internal shorts or open circuits can cause high voltage readings. Wiring Issues: Shorted or damaged wiring in the ignition coil control circuit. PCM Malfunction: In rare cases, a faulty PCM can incorrectly interpret or report voltage readings. Connector Problems: Corroded or loose connectors can disrupt the circuit and cause voltage fluctuations. Grounding Issues: Poor grounding can lead to voltage spikes in the control circuit. Excessive Resistance: High resistance in the circuit, possibly due to corrosion or damaged wires.
Diagnosis Tools Required: Multimeter, OBD-II scanner, wiring diagram. Initial Steps: Visually inspect the ignition coil and its wiring harness for damage. Check the connector for corrosion or loose connections. Use an OBD-II scanner to confirm the P1351 code and check for other related codes. Multimeter Testing: Measure the voltage at the ignition coil connector with the engine running. Compare readings to the manufacturer's specifications. Check the resistance of the ignition coil. Test the continuity of the wiring between the PCM and the ignition coil. OBD-II Scanner Data: Monitor the ignition coil's duty cycle and other relevant parameters using the OBD-II scanner. Component Isolation: Disconnect the ignition coil and retest the circuit to isolate the problem. Wiring Diagram Use: Consult a wiring diagram specific to the vehicle to trace the ignition coil control circuit and identify potential short circuits or open circuits. Damaged Wiring Harness: Rodent damage, chafing, or heat-induced damage to the wiring insulation. Loose Connectors: Vibration or corrosion can loosen connectors, creating intermittent high voltage readings. Internal Coil Failure: The coil's internal windings may be shorted, creating an abnormal resistance and voltage. PCM Driver Circuit Failure: The PCM's internal driver circuit for the ignition coil is malfunctioning. Interference: Electromagnetic interference (EMI) from other components affecting the control circuit. Aftermarket Modifications: Incorrectly installed aftermarket electrical components interfering with the ignition system.
Repair Ignition Coil Replacement: Replace the faulty ignition coil if it is determined to be the cause of the high voltage reading. Wiring Repair: Repair or replace damaged wiring in the ignition coil control circuit. This may involve splicing wires, replacing connectors, or rerouting the wiring harness. Connector Cleaning/Replacement: Clean corroded connectors with electrical contact cleaner. Replace damaged connectors. PCM Replacement: In rare cases, replace the PCM if it is determined to be faulty. Grounding Point Repair: Clean and secure grounding points to ensure proper electrical grounding. Wiring Harness Rerouting: Reroute the wiring harness to prevent chafing or contact with hot engine components. Professional Diagnosis: If you are unsure about the diagnosis or repair, consult a qualified mechanic. Improper Wiring Repair: Poorly executed wiring repairs can cause future problems. Incorrect Coil Installation: Failing to properly seat the ignition coil or torque the mounting bolts correctly. Ignoring Related Codes: Focusing solely on the P1351 code and neglecting other related DTCs. Using Incorrect Parts: Installing an incorrect or incompatible ignition coil. Failing to Clear Codes: Not clearing the DTCs after completing the repair, which can lead to misdiagnosis in the future. Neglecting Basic Inspection: Skipping the initial visual inspection of the wiring and connectors.

Detailed Explanations:

Basic Information:

  • Definition: The P1351 code specifically indicates that the PCM has registered a higher-than-normal voltage in the control circuit for a specific ignition coil. The "control circuit" is the wiring that the PCM uses to activate and de-activate the ignition coil, which then generates the spark to ignite the air-fuel mixture in the cylinder.
  • Affected Vehicles: While most commonly found in Ford, Lincoln, and Mercury vehicles, the underlying principle of ignition coil control circuits is similar across many makes and models. Therefore, a similar code could potentially arise in vehicles from other manufacturers, although the specific code number might differ.
  • Severity: The severity of the P1351 code can vary. A slight misfire might only cause a minor reduction in fuel economy and performance. However, a severe misfire can lead to catalytic converter damage, which is a costly repair.
  • Symptoms: The most common symptom is an engine misfire. This can manifest as rough idling, stumbling acceleration, and a general lack of power. The Check Engine Light (CEL) will also illuminate. Reduced fuel economy is a common consequence of the engine not running efficiently.
  • Related Codes: The P1351 code is often accompanied by other codes that specify which cylinder is misfiring (e.g., P0301 for cylinder 1 misfire). Other related codes might indicate problems with other ignition coils (e.g., P1352, P1353, etc.) or issues with the crankshaft position sensor or camshaft position sensor.

Diagnosis:

  • Tools Required: A multimeter is essential for measuring voltage, resistance, and continuity in the circuit. An OBD-II scanner is needed to read and clear diagnostic trouble codes. A wiring diagram specific to the vehicle is crucial for tracing the ignition coil control circuit.
  • Initial Steps: Begin with a visual inspection of the ignition coil and its wiring harness. Look for any signs of physical damage, such as cracks, frayed wires, or melted insulation. Check the connector for corrosion or loose connections.
  • Multimeter Testing: Measure the voltage at the ignition coil connector with the engine running. Compare the readings to the manufacturer's specifications (found in the vehicle's service manual). Check the resistance of the ignition coil itself. Test the continuity of the wiring between the PCM and the ignition coil to identify any breaks in the circuit.
  • OBD-II Scanner Data: Monitor the ignition coil's duty cycle using the OBD-II scanner. This can help identify if the PCM is commanding the coil correctly. Look for any abnormal readings or inconsistencies.
  • Component Isolation: Disconnecting the ignition coil and retesting the circuit can help isolate the problem. If the high voltage reading disappears when the coil is disconnected, the coil itself is likely the problem.
  • Wiring Diagram Use: A wiring diagram provides a detailed map of the ignition coil control circuit. This allows you to trace the circuit from the PCM to the coil and identify any potential short circuits or open circuits.

Repair:

  • Ignition Coil Replacement: If the ignition coil is determined to be faulty, replacing it is the most common solution. Be sure to use a high-quality replacement coil that is specifically designed for your vehicle.
  • Wiring Repair: Damaged wiring can be repaired by splicing wires together or replacing entire sections of the wiring harness. Ensure that all connections are properly insulated and protected from the elements.
  • Connector Cleaning/Replacement: Clean corroded connectors with electrical contact cleaner. If the connector is severely damaged, replace it with a new one.
  • PCM Replacement: PCM replacement should be considered as a last resort. Before replacing the PCM, thoroughly investigate all other potential causes of the P1351 code.
  • Grounding Point Repair: Clean and secure grounding points to ensure proper electrical grounding. Poor grounding can lead to voltage spikes in the control circuit.
  • Wiring Harness Rerouting: Reroute the wiring harness to prevent chafing or contact with hot engine components. This can help prevent future wiring damage.
  • Professional Diagnosis: If you are unsure about the diagnosis or repair, it is always best to consult a qualified mechanic. They have the expertise and tools to properly diagnose and repair the problem.

Frequently Asked Questions:

  • What does the P1351 code mean? The P1351 code indicates that the PCM has detected a high voltage in the control circuit for a specific ignition coil. This means the voltage is higher than what is expected.

  • Can I still drive my car with a P1351 code? While you can drive, it's not recommended. Continued driving with a misfire can damage the catalytic converter and reduce fuel efficiency.

  • How do I know which ignition coil is affected? The P1351 code often appears with other codes (e.g., P0301-P0308) that specify which cylinder is misfiring, thus identifying the affected coil.

  • Is it difficult to replace an ignition coil? Replacing an ignition coil is relatively straightforward on many vehicles, but it's important to disconnect the battery and follow the manufacturer's instructions.

  • Can a bad spark plug cause a P1351 code? While a bad spark plug itself won't directly trigger a P1351 code, it can contribute to misfires that might lead to other related codes and exacerbate existing ignition coil issues.

Conclusion:

The P1351 code signals a high voltage issue within the ignition coil control circuit, requiring prompt attention to prevent further engine damage. Thorough diagnosis using a multimeter, OBD-II scanner, and vehicle-specific wiring diagrams is crucial for identifying and rectifying the underlying cause, whether it's a faulty coil, wiring problems, or, in rare cases, a PCM malfunction.