If your Nissan vehicle has triggered the P1320 diagnostic trouble code, your engine’s ignition system isn’t communicating properly with the vehicle’s computer. This Nissan-specific code points to a malfunction in the primary ignition circuit—the electrical pathway that controls spark plug firing. While this is a moderate severity issue, it requires prompt attention to prevent engine damage and restore reliable operation.
What Does P1320 Mean?
P1320 is a manufacturer-specific code used by Nissan and Infiniti vehicles to indicate a fault in the Ignition Signal Primary Circuit. The primary circuit is the low-voltage electrical loop that connects the ignition control module (ICM) to the engine control unit (ECU). This circuit is responsible for triggering the ignition coil to fire the spark plugs at precisely the right moment during the engine cycle.
When the ECU detects an abnormal signal or loss of communication from the ignition control module, it sets code P1320. This could mean the signal is too weak, missing entirely, or the timing is off. Unlike generic OBD-II codes, P1320 is specific to Nissan’s proprietary diagnostic system and primarily affects 1990s to early 2000s Nissan and Infiniti models.
Common Symptoms
- Check Engine Light: The primary indicator—the MIL (malfunction indicator lamp) illuminates on your dashboard
- Engine Misfires: Rough idle, hesitation during acceleration, or noticeable stumbling while driving
- Hard Starting: Engine cranks but takes longer than normal to start, or fails to start entirely
- Stalling: Engine cuts out unexpectedly while driving or idling
- Reduced Power: Noticeable loss of acceleration and overall engine performance
- Rough Idle: Engine vibrates or shakes noticeably at traffic lights or in park
- No Start Condition: In severe cases, the engine won’t start at all
Possible Causes (Ranked by Frequency)
- Faulty Ignition Control Module (ICM): The most common cause. The ICM is responsible for managing the primary ignition circuit, and when it fails, the signal is lost or corrupted.
- Bad Crankshaft Position Sensor (CKP): This sensor provides timing data to the ignition system. A failing CKP sensor can cause incorrect or missing ignition signals.
- Corroded or Loose Connector Terminals: The connectors linking the ICM, ECU, and ignition coil can corrode or loosen, breaking the electrical connection.
- Damaged Wiring Harness: Broken, pinched, or chafed wires in the primary ignition circuit can interrupt signal transmission.
- Faulty Ignition Coil: A failing ignition coil can send abnormal feedback signals to the ECU, triggering the code.
- ECU Software Issue: Rarely, a corrupted engine control unit or outdated software can misinterpret normal ignition signals.
- Battery or Charging System Problem: Low system voltage can cause weak ignition signals, though this typically triggers other codes first.
Diagnostic Steps
Step 1: Verify the Code
Use an OBD-II scanner to confirm code P1320 is present. Check for any additional codes that might provide additional clues (such as P0335 for crankshaft position sensor faults).
Step 2: Visual Inspection
Inspect the ignition control module, ignition coil, and all related connectors for:
- Corrosion or white/green deposits on terminals
- Loose or partially disconnected connectors
- Damaged, pinched, or burnt wiring
- Water damage or moisture inside connectors
Step 3: Check Connector Integrity
Disconnect and reconnect all ignition system connectors. Clean any corroded terminals with a wire brush or electrical contact cleaner. Retest with the scanner to see if the code clears.
Step 4: Test the Crankshaft Position Sensor
Using a multimeter, check the CKP sensor resistance and voltage output. Compare readings to your vehicle’s factory specifications. A faulty sensor typically shows out-of-range values.
Step 5: Test the Ignition Control Module
With the ignition on (engine off), measure voltage at the ICM connector. You should see battery voltage (approximately 12V). If voltage is absent or very low, there’s a wiring issue. If voltage is present but the code persists, the ICM likely needs replacement.
Step 6: Scope Testing (Advanced)
If available, use an oscilloscope to monitor the ignition signal waveform. The signal should show a clean square wave pattern. Distorted or missing waveforms confirm a primary circuit failure.
Step 7: ECU Scan
Have a Nissan dealership or qualified technician perform a full ECU scan to rule out software issues or other underlying problems.
Repair Cost Estimates
DIY Repairs:
- Connector cleaning and terminal repair: $0–$50 (parts only)
- Wiring harness repair or replacement: $50–$200 (parts and supplies)
Professional Shop Repairs:
- Ignition Control Module replacement: $300–$600 (parts + labor)
- Crankshaft Position Sensor replacement: $150–$350 (parts + labor)
- Ignition Coil replacement: $200–$400 (parts + labor)
- Full ignition system diagnosis and repair: $400–$800 (parts + labor)
Nissan Dealership Repairs:
- Full diagnostic and repair: $600–$1,200 (higher labor rates)
Note: Costs vary by location, vehicle year, and complexity. Always get a written estimate before authorizing repairs.
Can I Still Drive?
Severity: Moderate
While P1320 is not an immediate “pull over now” emergency, you should not ignore it. Here’s what you need to know:
- Short Trips: You may be able to drive short distances to a repair shop, but performance will be compromised.
- Highway Driving: Not recommended. The vehicle may stall unexpectedly, creating a safety hazard.
- Extended Driving: Continued operation can damage the catalytic converter and cause additional engine damage.
- Risk of Stalling: The engine could cut out at any time, potentially in traffic or at an intersection.
Best Practice: Have the vehicle diagnosed and repaired within 24–48 hours. If you experience severe misfiring, hard starting, or repeated stalling, stop driving immediately and have it towed to a repair facility.
Frequently Asked Questions
Can a loose gas cap cause code P1320?
No. A loose gas cap typically triggers P0455 (Evaporative Emission System Leak Detected). P1320 is specific to the ignition system’s primary circuit and requires attention to electrical components, not fuel system components.
Will clearing the code fix the problem?
Temporarily clearing the code with a scanner will not fix the underlying issue. The code will return once the vehicle is driven again. You must diagnose and repair the root cause—whether that’s a faulty ICM, bad sensor, or wiring problem—to permanently resolve the issue.
Is P1320 the same as P0320?
No. P0320 is a generic OBD-II code for “Ignition/Distributor Engine Speed Input Circuit,” while P1320 is Nissan’s manufacturer-specific code for the primary ignition circuit. They indicate similar problems but are specific to different systems and manufacturers.
Can I replace the ignition control module myself?
Possibly, depending on your mechanical skill level. The ICM is typically located under the hood and requires basic disconnection of connectors and removal of mounting bolts. However, if you’re not comfortable with electrical work, professional installation is recommended to ensure proper configuration and avoid additional damage.