1998 V70XC P0330 (Knock Sensor)

[bubbeck]

Also sounds like I might in luck and can remove the throttle body instead of the intake manifold. Any reason not to do this?

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[DeadEric]

written a few posts ago...

Knock sensors use piezoelectric crystals to convert vibrations into voltage. The ecu sees the voltage spike at the wrong time and assumes that you're having detonation (combustion before spark) and adjusts timing to compensate (if applicable and to the degree that it can.) When the ecu cannot compensate for detonation the code is set (speaking most cars not Volvo specifically.)

If you have detonation you'll be able to hear/feel it. The pistons "ring" inside the cylinders from combustion occurring too soon before tdc and have to travel thru the force of combustion to reach the end of the stroke before moving down. It's also referred to a spark knock as it does make a knocking sound.

Knock, knock...

Who's there?

Spark knock.

Spark knock, who?

Spark knock something, something funny cuz you waited too long and need a new engine. (Haven't been able to work that one out to make it funny.)

As far as testing a knock sensor, the voltage should be 0 if there is no vibration. Knock sensor unplugged and volt meter touching the leads, engine off. Light tapping in the engine with a small hammer will create voltage spikes.

[jimmy57]

Knock sensor codes are just of never caused by fuel. 87 octan at 5000 feet plus is usually sufficient unless you tow or drive flat up up the pass to IKE. The knock sensors make miniscule current moderate voltage spikes in response to the internal crystal shock from knock. The connectors having ANY issues with corrosion or low female side tension will cause the codes. Inspection of that connector shown in one of the earlier replies is where is starts. The code sets when the engine speed and calculated load exceeds threshold values and no minimal signal is detected. There will always be some knock sensor signalling at higher engine speeds with even light loading. The signal value for knocking responses is an increasing scale with engine speed. The knock sensors do have to be secure to block but I have never had any issue years later unless the knock sensors have been disturbed for a repair. You stand a good chance of repairing it with contact cleaner spray and dielectric grease (wheel bearing and most chassis grease has metal additives for better wear, dielectric grease is a higher temp melt point grease with nothing added, just the moistureproofing effects of the lubricant.

[bubbeck]

Hmm well based on your advice, I hit the connector with some contact cleaner and put some dielectric grease on it, and so far so good, no code with 1500 miles on the clock... Will update it rears its ugly head again.