Nissan Pathfinder Won T Start

Okay, so your Nissan Pathfinder won't start. That's a frustrating situation, but don't panic. The good news is that a no-start condition, while potentially complex, can often be diagnosed with some logical troubleshooting. This article will guide you through common causes and diagnostic procedures, assuming you have a basic understanding of automotive systems and some tools at your disposal. We'll cover everything from simple oversights to more involved electrical issues. Remember to always disconnect the negative battery terminal before working on electrical components to prevent accidental shorts.

Basic Checks: The Low-Hanging Fruit

Before diving into deeper diagnostics, let's cover the easy stuff. These might seem obvious, but they're often overlooked.

1. The Obvious: Fuel and Battery

Fuel Gauge: Is there actually fuel in the tank? The gauge might be faulty. If you're suspicious, add a gallon or two and try again.

Battery Voltage: This is crucial. Even if the lights come on, the battery might not have enough cranking amps to turn the engine over. Use a multimeter to check the battery voltage. A healthy battery should read around 12.6 volts at rest. Anything below 12 volts indicates a discharged battery. A jump start can help determine if the battery is the issue. If it starts with a jump, investigate the battery, alternator, or parasitic drain.

Battery Terminals: Check for corrosion on the battery terminals. Clean them thoroughly with a wire brush and battery terminal cleaner. Ensure they're tight and making good contact.

Loose Connections: Trace the battery cables to the starter and ground points. Look for loose, corroded, or damaged connections. Clean and tighten as needed. A bad ground can prevent the starter from receiving sufficient current.

2. Ignition System: Key and Security

Key Fob Battery: If your Pathfinder has a keyless entry system, a dead key fob battery can prevent the vehicle from starting. Try using the physical key (if available) or replace the battery in the fob.

Immobilizer System: The immobilizer system is designed to prevent theft. If the system isn't recognizing your key, it will prevent the engine from starting. Symptoms include the security light flashing on the dashboard. Try the following:

a. Ensure the key is fully inserted into the ignition.

b. Try a different key if you have one. A faulty transponder chip in the key can be the problem.

c. Consult your owner's manual for the immobilizer reset procedure. Some models require a specific sequence of turning the key on and off.

If the immobilizer continues to be an issue, it might require professional diagnosis and reprogramming.

Diagnosing the Problem: Fuel, Spark, and Compression

The engine needs three things to run: fuel, spark, and compression. We'll systematically check each of these.

1. Fuel System Diagnosis

Fuel Pump Relay: The fuel pump relay provides power to the fuel pump. It's often located in the under-hood fuse box. Consult your owner's manual for its exact location. To test it:

a. Locate the relay and the corresponding relay for a known working system (e.g., the horn relay, if it’s the same type).

b. Swap the relays. If the car starts, the original relay is bad.

c. If swapping doesn't work, use a multimeter to check for power at the relay socket when the ignition is turned on. You should see 12V at one of the terminals. If not, there's a wiring issue.

Fuel Pump: If the relay is good, the fuel pump itself might be failing. To test this, you'll need to access the fuel pump. The process varies depending on the Pathfinder model. Some have an access panel under the rear seat; others require dropping the fuel tank.

a. Safety First: Disconnect the negative battery terminal. Work in a well-ventilated area away from open flames. Have a fire extinguisher handy.

b. Locate the fuel pump connector. Use a multimeter to check for voltage at the connector when the ignition is turned on. If you have voltage but the pump isn't running, the pump is likely bad.

c. You can also try listening for the fuel pump priming when you turn the key to the "on" position. You should hear a whirring sound for a couple of seconds. No sound indicates a potential pump failure.

Fuel Filter: A clogged fuel filter can restrict fuel flow. While less common, it's a possibility. Locate the fuel filter (usually along the fuel line) and replace it. Note the direction of flow and install the new filter correctly.

Fuel Injectors: While less likely to cause a complete no-start, clogged fuel injectors can contribute to the problem. They usually show other symptoms like rough idle. If you've ruled out other issues, consider a fuel injector cleaner or professional injector cleaning service.

2. Ignition System Diagnosis

Spark Plugs: While unlikely to cause a complete no-start unless severely fouled, check the spark plugs. Remove one and inspect it. Look for excessive wear, carbon buildup, or oil fouling. If the plugs are old or in poor condition, replace them.

Ignition Coils: Modern Pathfinders use coil-on-plug ignition, meaning each spark plug has its own ignition coil. A faulty coil can prevent spark. To test them:

a. Obtain a spark tester. This is an inexpensive tool that allows you to visually confirm spark.

b. Disconnect the coil from the spark plug.

c. Connect the spark tester between the coil and the spark plug.

d. Have someone crank the engine. You should see a bright spark jumping across the tester's gap. No spark indicates a faulty coil.

e. You can also try swapping coils between cylinders. If the no-spark condition moves to a different cylinder, the coil is bad.

Crankshaft Position Sensor (CKP) and Camshaft Position Sensor (CMP): These sensors are critical for timing the ignition and fuel injection. A faulty CKP or CMP sensor can prevent the engine from starting. These sensors provide engine speed and position information to the ECU. If the ECU doesn’t receive a signal from them, it won’t trigger the ignition or fuel injection.

a. Symptoms: In addition to a no-start, you might see a check engine light (CEL) with codes related to the CKP or CMP sensors.

b. Testing: Use a multimeter to check the sensor's resistance and output voltage. Consult your Pathfinder's repair manual for the correct values and testing procedure. An oscilloscope is the best tool to check the signal waveform.

c. Location: The CKP sensor is typically located near the crankshaft pulley, while the CMP sensor is located near the camshaft. The exact location varies by engine model.

Distributor (If Applicable): Older Pathfinders may have a distributor. Check the distributor cap and rotor for cracks, corrosion, or damage. Ensure the distributor is properly timed.

3. Compression Diagnosis

While less common, a loss of compression can prevent the engine from starting. This is usually a sign of a more serious mechanical issue. A compression test is needed.

a. Remove all spark plugs.

b. Insert a compression tester into each spark plug hole, one at a time.

c. Crank the engine for several seconds and record the compression reading.

d. Compare the readings to the manufacturer's specifications. Low compression in one or more cylinders indicates a potential problem with valves, rings, or head gasket.

If you find low compression, further investigation is needed, possibly involving a leak-down test to pinpoint the source of the leak.

Scanning for Diagnostic Trouble Codes (DTCs)

Even if the check engine light isn't illuminated, there might be stored diagnostic trouble codes (DTCs) that can provide valuable clues. Use an OBD-II scanner to retrieve any codes. Research the codes to understand their meaning and potential causes. Common codes related to no-start conditions include those for the CKP sensor, CMP sensor, fuel pump relay, and immobilizer system. Clearing codes without addressing the underlying problem will not fix the issue.

Electrical System Issues

Fuses and Relays: Check all fuses and relays related to the fuel system, ignition system, and ECU. Use a test light or multimeter to verify that each fuse has power on both sides. A blown fuse indicates a short circuit in the corresponding circuit.

Wiring Harnesses: Inspect wiring harnesses for damage, such as frayed wires, broken connectors, or corrosion. Pay close attention to harnesses near the engine, exhaust, and areas prone to moisture. Use a multimeter to check for continuity and shorts in the wiring.

ECU (Engine Control Unit): While rare, a faulty ECU can cause a no-start condition. This is usually a last resort diagnosis after ruling out all other possibilities. If you suspect the ECU, it's best to consult a qualified mechanic for diagnosis and replacement.

Conclusion

Troubleshooting a no-start condition on a Nissan Pathfinder requires a systematic approach. Start with the basics, then move on to more advanced diagnostics. By carefully checking the fuel system, ignition system, and compression, and by using an OBD-II scanner, you can often pinpoint the cause of the problem and get your Pathfinder back on the road. If you're uncomfortable with any of these procedures, it's always best to consult a qualified mechanic.