Knock Sensor #2 (P0330) and other symptoms

[Bambusiero]

Engine Control Experts - opinions and interpretations invited.

Many here have reported problems with error code P0330, Knock Sensor #2, and it has usually been due to broken wiring or connection to the sensor, or an actual bad sensor.

I've had an intermittent P0330 for some time now, but recently it has become persistent, and I now believe it is an indicator of some other real engine problem.
There's conflicting evidence...

NOTE: I assume here that Knock Sensor #1 is toward the front of the engine (cylinders 1,2,3) and #2 is towards the back (cylinders 4,5,6). The FSM is not explicit about it, but that's how others have documented it.

Here's what I have done so far:

1) Checked wire harness continuity (opens and shorts) from both Knock Sensor #1 to Engine Control Module (ECM) connector E5(B) pin 6, and Knock Sensor #2 to E5(B) pin 14. Both are OK.

The ECM is in front of the passenger's right knee, and very awkward to probe.
(By the way, on mine, the wire for #1 E5(B)-6 is Red/Silver Dot, not Black like the LX450 1997 Electrical Wiring Diagram says on page 66.)

2) Checked the signal for both at the ECM connector with an o-scope at 4000 rpm. Looked OK I guess. It's a difficult signal to get a good picture of, but there was active signal on both, indicating both sensors are live.

3) Swapped sensors from front to back. P0330 returned, so:
- Both sensors are good.
- Maybe the wire for #2 is bad as a signal transmission line, somehow degrading the signal, even though it has continuity?
- Maybe the ECM input signal conditioning for #2 is degraded?
- Maybe there really is knocking on just one of the back 3 cylinders, and the ECM is misinterpreting it because it's different than all the others?

4) The truck seems to be very sensitive to poor quality gas, with loaded hot uphill conditions struggling to keep speed, even in 2nd gear, and coolant temp quickly rising. Premium gas did not struggle (well, not as much) in similar conditions.

5) P0330 stayed cleared on an evening highway trip at higher elevations, including long climbs, but come back when I got down to the lowlands. It would then come back within 30 seconds, with or without A/C running. Temperatures were relatively mild (for Phoenix), and coolant temp was low 190's.
- Maybe one cylinder getting lean at low elevations, but more of a match to the others at high elevations?

6) Here's the confusing one. I pulled the plugs. Cylinder #1 really looks like a problem. 2-6 look fine. That should be P0325, Knock Sensor #1, right?

My guess is a bad/plugged injector.
Any other possibilities?
What can cause this confusion of symptoms between front and back knock sensors?

 

[huntir]

Sorry I have no advice....I also have that problem,accept both
Of my sensors are giving me the code! I do know that when this
happens it retards your timing which takes the umph! out of engine!
So I hope some experts on this subject chime in.

 

[inkpot]

Howdy! So far I have been fortunate enough to not have any of these codes pop up, yet. So, no hands on experience to help you out with. My first thought was that the wiring for the two sensors is flopped somewhere in the system. Can you disconnect one sensor completely in order to force a code, thereby knowing if they are in fact reversed? Have you ever replaced your plugs and/or plug wires? Looks like #1 needs some help. Maybe there is a misfire, just bad enough to trip the knock sensor, but not the ox sensor? How's the ignition timing look? Could it be a problem with the crank position sensor? When I can't identify the actual cause of a problem, I always start with the cheap and easy stuff and work up from there. John

 

[Bambusiero]

I was thinking about that idea too, of pulling each sensor wire to deliberately throw a code to double check the whole system's agreement about which is which. Just haven't gotten around to it yet.

I had the head gasket job done about 20k miles ago, and I assume/hope that plugs were replaced then, but don't know for sure. I'm heading out now to get a new set of plugs, since they're already out. Plug wires? Probably original. They Ohm out OK, ranging from 7.5K Ohms (#1) and up to 17K Ohms. Spec is 25K Ohms max.

I have not checked the overall timing.

Can the crank position sensor be damaged/off for just one cylinder?

 

[ed97fzj80]

I support your injector theory.

 

[kidglove13]

It might be an injector thing but you really need to test the knock sensors
Did you do the PHH recently?
The plug and sensor are very sensitive to being hit or jarred
And how are you resetting the check engine light?
I have found it works best if you disconect the battery and allow the ECU to relearn

 

[inkpot]

If you have OEM plug wires, they will have the production year stamped on them.

 

[Bambusiero]

Ah - I'll have a look for the plug wire production year. Thanks.

The knock sensors have been tested to the extent of:
- Ohm meter - high resistance - open ckt - good.
- Physical inspection - connectors are intact - no damage.
- Oscilloscope at 4000 rpm at the ECM input pins - active AC signal on both, roughly similar amplitude. Waveform is too variable to really capture.
- Swapped #1 and #2 (front to back) - P0330 returned. Did not turn into P0325.

The PHH got changed during the major headgasket service, so everything was apart then.

I have a ScanGaugeII installed, which can read and clear OBDII codes.

I decided to clean up spark plugs #1 (hard ashy buildup) and #4 (pretty clean) and swap them, and re-check in a few days. We'll see.

 

[alia176]

I have a similar scenario ever since both of my 80s have head gasket swapped. I too am getting a knock sensor CEL code. At a cost of $142/ea, I'd like to make sure that is indeed the issue! The '97 has an intermittent P325 code and the '96 has a steady P325 code.

Let us know what you find out.

 

[landtank]

Check the injector plug. I've noticed on a few injectors that the tap that the female plug latches onto are breaking off.

 

[alia176]

Check the injector plug. I've noticed on a few injectors that the tap that the female plug latches onto are breaking off.

Excellent advice Rick. The knocking is a symptom caused by perhaps running too lean. I'll look at the injectors like you mentioned. Another clue is that I rec'd a second code. Can't recall the exact number but the description was "bank 1 too lean" or something like that.

 

[THEJOCKER]

Question

Bambusiero,
I just checking right now my knock sensor, because i changed but still the 55 error code on my truck, between both knock sensors connectors wires has continuity?

 

[alia176]

Curious as to the cause of the P330 code turned out to be!

 

[SmokingRocks]

in this boat right now........

Code 55, rebuilt engine 10k miles ago, broke one sensor in the process and replaced it. The one I replaced is the one that is throwing the code. The sensor passes its test, and the conduit path to the ECU is good. Although the wire into the connector did have a break in the insulation.

I guess I'll swap the front to back but I'm not sure whats going on here.

 

[landtank]

I've had a few since this thread started and it's the sensor itself as far as I can see. There are a lot of cheap sensors out now and most are junk.

 

[SmokingRocks]

IIRC the replacement sensor was a cheapy.

It did produce voltage when I tested it, but who knows could be too sensitive.

 

[ZRTALPHA1]

Does anyone know what the reading should be when testing the knock sensor. I just finished replacing the injector seals, intake gaskets and all the vacuum lines to get rid of an egr code and now I have a knock sensor code. Any help would be appreciated

 

[landtank]

if you are getting a sensor code it's likely the sensor. I've replaced 4 sets last year all with sensor codes. Seems to be getting more common as they get older

 

[ZRTALPHA1]

if you are getting a sensor code it's likely the sensor. I've replaced 4 sets last year all with sensor codes. Seems to be getting more common as they get older

I hope thats all it is, I will check the wire going to the sensor tomorrow. Thanks i will update.

 

[ZRTALPHA1]

I hope thats all it is, I will check the wire going to the sensor tomorrow. Thanks i will update.

Well I have some good news and some bad news, good news is the knock sensor is just broken and its not some other major issue. Bad news is I have to buy a new one. Thanks for your help, I love this forum!