Knock sensor P0331

Post by **ZionXIX** » 02 Mar 2020, 10:01

Last night I tripped a P0331 knock sensor code under hard acceleration merging onto the highway. There was no noticeable performance changes. I reset the code and it hasn't come back. I'm curious why it tripped in the first place.

Post by **RickHaleParker** » 02 Mar 2020, 12:48

P0331 = 4-3-3 No rear knock sensor signal.

The signal went missing. Check and clean the Rear Knock sensor electrical connector. Check the wiring for shorts and opens. It could also be at the ECM side of the connection.

Bare wire that shorts out when the engine moves.
Wire broken under the insulation, opens when the wire is pulled on.
Electrical connector losing contact under stress.

Post by **erikv11** » 02 Mar 2020, 16:23

Spurious knock sensor codes are common, in all likelihood the code will not come back and to my mind there is not much use in trying to speculate why it happened.

Great info from Rick, if it comes back check the wiring like Rick says. The sensors basically do not go bad, but the wiring/connectors do.

Post by **ZionXIX** » 02 Mar 2020, 20:13

Good to know. I'm not even sure where the sensors are.

Post by **RickHaleParker** » 02 Mar 2020, 21:08

ZionXIX wrote: ↑02 Mar 2020, 20:13 Good to know. I'm not even sure where the sensors are.

One on the front of the engine and one on the back of the engine. They look like this.
$168.07 that is why I say, check the wiring and connectors first.

Post by **erikv11** » 02 Mar 2020, 22:53

RickHaleParker wrote: ↑02 Mar 2020, 21:08 ... One on the front of the engine and one on the back of the engine. ...

Oops, not even close.

Both knock sensors are on one side of the engine, under the intake manifold. Checking the wiring is a PITA without removing the IM but you can do it. Easier on an NA obviously. I wouldn't bother if the codes don't recur but keep it in mind as something to eyeball during that next PCV job.

Don't sweat that high price tag for new ones. The junkyard is full of knock sensors and they are all working just fine. It is just a simple microphone, the sensors don't go bad but the wiring can.

Post by **abscate** » 03 Mar 2020, 01:17

Pedantically, the left side of the engine, one under the PCV BOX and one relatively exposed more to the left side of car. This is towards the front of the car. People have reported servicing these without removing the intake manifold but I don’t see how.

They indeed seldom die. I have two from parts cars if a junk run is inconvenient.

Post by **RickHaleParker** » 03 Mar 2020, 02:07

abscate wrote: ↑03 Mar 2020, 01:17 Pedantically, the left side of the engine,

Pedantically there are two front knock sensors because Left, Right, Front and Rear is determined by sitting in the car and looking out the windshield.

abscate wrote: ↑03 Mar 2020, 01:17 People have reported servicing these without removing the intake manifold but I don’t see how.

That where kids come in handy, the tiny hands. It is why my dad had me turning bolts at 7 years old.

Post by **abscate** » 03 Mar 2020, 06:22

deleted totally wrong post

Post by **erikv11** » 03 Mar 2020, 09:06

abscate wrote: ↑03 Mar 2020, 01:17 Pedantically, the left side of the engine, one under the PCV BOX and one relatively exposed more to the left side of car. This is towards the front of the car. People have reported servicing these without removing the intake manifold but I don’t see how.

They indeed seldom die. I have two from parts cars if a junk run is inconvenient.

Pedantically (that's me!), the right side of the engine. Timing belt on the front (think "front cam seals"), PCV on the right, exhaust on the left, rear cam seals on the rear.

The main point is to let people know the knock sensors are both on the same side of the engine.