P1370 Code? Here’s How to Fix It Quickly and Easily

The P1370 code is a manufacturer-specific powertrain code. Its exact definition depends on the vehicle application, but it most commonly indicates a fault in the ignition control module’s 4X reference circuit.

This code identifies a detected signal or circuit condition, not necessarily a failed module. Proper diagnosis requires verifying the exact factory definition and testing the relevant reference circuits.

Key Takeaways

• The P1370 code is manufacturer-specific, commonly indicating an Ignition Control Module 4X reference circuit fault on GM applications.
• Possible causes include damaged wiring, poor electrical connections, a faulty crankshaft position sensor, or a failed ignition control module.
• Symptoms typically include an illuminated Check Engine Light, engine misfires, rough idle, and stalling.
• Diagnosis requires confirming the exact factory definition and testing the 4X reference signal and related sensor circuits.
• Repairs depend on the confirmed fault and may involve wiring repair, sensor replacement, or module replacement.

P1370 Code Description and Implications

P1370 is a manufacturer-specific trouble code. Its exact definition depends entirely on the vehicle application.

Some General Motors (GM) applications: The code indicates an “Ignition Control (IC) Module 4X Reference Circuit” fault. The Powertrain Control Module (PCM) monitors the 4X reference pulses generated by the IC module and detects an abnormal number of pulses or a missing signal.

Certain Ford applications: The code may relate to a spark test RPM or ignition coil primary circuit fault. Because definitions vary, verifying the exact factory service information is mandatory.

Common Causes of the P1370 Code

Several conditions can trigger this manufacturer-specific malfunction code. Identifying the exact cause requires electrical testing of the specific circuit.

• For GM applications: A failing crankshaft position sensor, damaged wiring between the sensor and the IC module, or a faulty IC module.
• Poor electrical connections, corroded connectors, or loose pins in the 4X reference circuit.
• Electrical interference from damaged secondary ignition components, such as arcing spark plug wires.
• A faulty PCM or internal module driver issue (rare, usually only after circuit verification).

Symptoms Associated With P1370

Symptoms vary depending on the specific system design and the underlying fault condition.

• Illuminated Check Engine Light.
• Engine misfires, rough idle, or hesitation during acceleration.
• Engine stalling or a no-start condition if the PCM loses the critical reference signal required for fuel injection and spark timing.
• Reduced engine power or the vehicle entering a fail-safe mode.

Diagnosing the P1370 Trouble Code

Diagnosis must begin by confirming the exact factory definition and inspecting the physical system components.

• Verify the exact manufacturer definition and locate the wiring diagram for the specific 4X reference or ignition circuit.
• Visually inspect the wiring harness and connectors at the IC module, crankshaft position sensor, and PCM for damage, chafing, or corrosion.
• Use a digital multimeter or oscilloscope to test the 4X reference signal waveform and verify circuit continuity.
• Check for related codes, such as P0335 (Crankshaft Position Sensor Circuit), which may indicate a broader sensor issue.

Repairing the P1370 Issue

Repairs depend entirely on the confirmed root cause of the system malfunction.

• If wiring damage or an open/short circuit is found, repair or replace the affected harness sections and secure the routing.
• Clean or replace corroded connectors to restore proper electrical contact and circuit integrity.
• If the crankshaft position sensor or IC module fails electrical or functional testing, replace it using a component meeting the correct vehicle specification.
• If testing confirms the PCM is faulty and all external circuits are intact, follow the manufacturer procedure for module replacement.

Cost Considerations for P1370 Repairs

Cost depends on diagnostic time, component accessibility, required parts, programming requirements, and labor.

Replacing an externally mounted sensor or repairing a wire is generally less expensive than diagnosing and replacing an Ignition Control Module or performing complex wiring repairs.

Prevention Strategies for Future Occurrences

While electrical and mechanical failures are not always preventable, some practices can reduce the risk of sensor and ignition issues.

• Inspecting exposed wiring and connectors can help identify developing damage from heat exposure, chafing, or road debris.
• Keeping electrical connections clean and sealed helps prevent moisture intrusion and corrosion.
• Replacing secondary ignition components before they degrade can prevent electrical interference that disrupts sensitive reference signals.

Troubleshooting Tips and Best Practices

Always consult the exact manufacturer service information for your vehicle’s wiring diagram and expected signal waveforms.

• Do not assume the IC module is faulty simply because the code points to the 4X reference circuit; wiring damage and poor connections must be ruled out first.
• On GM applications, verifying the 4X signal against the 24X signal (if equipped) can help isolate whether the fault lies with the sensor, the wiring, or the module.
• Verify technical service bulletins for your specific make and model, as some manufacturers issue updated wiring harnesses or revised sensor part numbers for recurring signal faults.

More OBD-II Codes

Frequently Asked Questions

Is the P1370 code generic or manufacturer-specific?

No. P1370 is a manufacturer-specific code. Its exact definition varies by vehicle make, most commonly indicating an Ignition Control Module 4X reference circuit fault.

Can I drive my car with a P1370 code?

It depends on the symptoms. If the engine is stalling, misfiring severely, or failing to start due to a missing reference signal, the vehicle is unsafe or impossible to drive.

Will a bad crankshaft position sensor cause a P1370 code?

Yes. On GM applications, a failing crankshaft position sensor will disrupt the signal sent to the Ignition Control Module, triggering this specific reference circuit malfunction code.

Can a wiring issue trigger the P1370 code?

Yes. An open circuit, short to ground, or high resistance in the 4X reference signal wire between the Ignition Control Module and the PCM will cause a signal fault.

Will a P1370 code cause an emissions test failure?

Yes. Any code that illuminates the Check Engine Light or indicates an active misfire or ignition system fault will cause an automatic failure during an OBD-II emissions inspection.

What Should You Do About the P1370 Code?

Confirm the exact factory definition for your specific vehicle application. Follow the applicable manufacturer diagnostic procedure to test the relevant ignition control circuits, reference signals, and sensors.

Repair or replace the confirmed failed component or fix the identified wiring fault, then retest the system to ensure proper operation.