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2001 Nissan Pathfinder 3.5L Engine Faults: P1145, P0505, and P0304 Diagnosis & Fixes

Model: 2001 Nissan Pathfinder Fault Code: P0304 Posted: 2017-08-10 14:53

Hello, my name is Jesse. I own a 2001 Nissan Pathfinder SE with approximately 196,800 miles. The vehicle is currently exhibiting multiple engine issues indicated by the following diagnostic trouble codes: P1145, P0505, and P0304. I have already replaced the idle air control valve (IAC) and the camshaft position sensor. I've also removed and inspected the spark plugs, checked all electrical connections, and performed basic diagnostics. Despite these efforts, the check engine light remains on—flashing after short drives (less than 1/4 mile), and the codes persist even after clearing them. I'm now at a loss as to what might be causing this. I'm considering more advanced troubleshooting or even engine replacement, but I'd greatly appreciate any expert advice from experienced mechanics or owners of similar vehicles. Any insights into how these specific codes relate to actual component failures would be incredibly helpful.

Related fault codes
P0304P0505P1145
Comments (9)
Anonymous 2017-08-10 14:54

I believe you meant to specify a 3.5L V6 engine—this is important for accurate troubleshooting and part compatibility.

Anonymous 2017-08-10 16:06

Do you have access to an OBD2 scanner that can display live data? For codes P0505 (idle control system malfunction) and P1145 (throttle position sensor issue), start with circuit integrity checks. For P0304 (cylinder 4 misfire), verify spark at the plug—check if it's wet, black, or tan. Is there fuel injection? Try a coil or injector swap to isolate the fault. A fuel additive like Seafoam can help clear carbon buildup before disassembling components. If spark and fuel are confirmed, proceed with compression and vacuum tests. Always prefer OEM Nissan parts when replacing sensors or valves.

Anonymous 2017-08-10 16:24

I checked the spark plugs—initially, the gap was significantly off. I cleaned them with a wire brush; they now appear slightly grey. I plan to perform a coil swap between cylinders to test if the misfire code follows. My main concerns remain the idle air control valve and camshaft position sensor. Both were replaced, yet the engine management computer (EMC) continues to trigger these codes. A friend with a high-end scanner confirmed the same readings on my vehicle. After clearing the codes, they return shortly after driving—especially during short trips where the check engine light flashes.

Anonymous 2017-08-10 16:25

Sorry for the poor spelling—I have dyslexia and it makes writing difficult.

Anonymous 2017-08-10 17:23

It's critical to understand that a diagnostic code does not mean a part is faulty. Auto parts stores often suggest replacement based on codes because they sell parts. A code simply indicates the sensor is not reporting expected values or isn't communicating properly with the Powertrain Control Module (PCM).

Anonymous 2017-08-11 01:30

The sensors I removed were heavily coated in burnt grime—this suggests contamination, which may be interfering with accurate readings and causing false codes.

Anonymous 2017-08-11 06:07

Let’s start with simple, fundamental checks: What is the engine idle RPM at operating temperature? Are spark plugs firing correctly? And are these three codes the only ones present?

Anonymous 2017-08-11 08:08

The engine idles steadily around 1400 RPM when warm. I believe spark plug ignition is functioning properly.

Anonymous 2017-08-11 08:52

Simple troubleshooting steps to try: Check for vacuum leaks—use the old-school spray bottle method (spray carburetor or intake hoses while idling). If spark is confirmed, inspect fuel injection. Try a fuel treatment like Seafoam to clean injectors and combustion chambers before replacing any components.