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1997 Pontiac Sunfire P0325 Code Reappears After Knock Sensor Replacement - Troubleshooting Guide

Model: 97 Sunfire Fault Code: P0329 Posted: 2018-10-18 11:55

I recently purchased a 1997 Pontiac Sunfire with 125,000 miles on the odometer. Upon inspection, it had two existing trouble codes: P0300 and P0325. I replaced the original Champion copper spark plugs with NGK iridium plugs, which significantly improved idle stability. I also installed a new knock sensor as recommended. After clearing both codes using my OBD-II scanner, I took the car for a drive. The P0300 code remained resolved, but the P0325 code returned shortly after. Despite removing and reinstalling the knock sensor multiple times, the issue persists. I'm now looking for further diagnostic steps. Is it possible that there's an electrical connection or wiring issue with the knock sensor? Or could there be a problem with the engine control module (PCM) reading the signal incorrectly? I've tried checking the AC voltage on the knock sensor wire and confirmed proper installation—no sealant was used since the sensor does not sit in the water jacket, and the mounting hardware was tightened to specification. The fault appears intermittent: the check engine light goes off for a few days, then returns intermittently. This makes troubleshooting especially difficult. I'm considering whether it's time to consult a professional mechanic with access to a diagnostic tool capable of testing PCM pin continuity or performing live sensor signal analysis.

Related fault codes
P0329
Comments (2)
Anonymous 2018-10-18 14:40

Check for any engine noises or exhaust leaks. Verify the wiring harness from the knock sensor to the PCM is intact and properly connected. Measure AC voltage on the knock sensor wire using a multimeter. Ensure correct torque during installation, no sealant used (since this sensor does not go into the coolant jacket), and all connections are secure.

Anonymous 2018-10-18 14:50

This is a 2.4L Twin Cam engine—important to note for diagnostics. No unusual engine noises or exhaust leaks have been detected. I haven't yet removed the PCM to test continuity on the correct pin for ground connection. Accessing the area was extremely tight; I only managed to get a wrench in, and tightened it as much as possible without tools. No sealant was applied because the knock sensor does not interface with the water jacket. The wiring appears physically intact. The issue is intermittent—the check engine light turns off for several days before returning sporadically. This makes consistent diagnosis challenging.