How in the hell can an OEM KS fail less than ONE year after installing it???
If the code P0325 is stored in the ECU, does it mean that the KS was operating and performed the designated function, or is it kaput altogether? What are the chances of an OEM part like this failing less than one year later?

It's pretty easy to read codes on your Q with an OBD2 code reader. I would clear the code, start your engine for just a few seconds and then go back and read the codes again. If the KS code comes back that quickly then it's dead. You should also be able to ohm test the KS at the connector which on the 90-95 Q is on the passenger side of the plenum. Instructions are at Q45.org. I suspect that your MY will be the same as the 90-95 OBD1 engines.

goody90q45 wrote:It's pretty easy to read codes on your Q with an OBD2 code reader. I would clear the code, start your engine for just a few seconds and then go back and read the codes again. If the KS code comes back that quickly then it's dead. You should also be able to ohm test the KS at the connector which on the 90-95 Q is on the passenger side of the plenum. Instructions are at Q45.org. I suspect that your MY will be the same as the 90-95 OBD1 engines.

Ya, I totally understand that they fail.... but how do OEM sensors fail so soon? Shouldn't they be worth at least two years? I mean.. c'mon... WTF man? BTW... I cleared the code once already and it came back again...

Did you replace the subharness at the same time? They're known to fail too.

Did you buy the OEM sensors from a dealership or outside source? Supposedly counterfeits are common on places like ebay.

Heath

No, I didn't replace the subharness... I bought it, but Paranoidjack said I didn't need them... you're just talking about the pigtail wire plug that goes directly on the harness? Right? The ones that NAPA sold me had two wires on them, and there is only one wire on the harness...
So which one is P0325??? passenger or Driver side??? The local Dealership isn't giving me any answers...
I know there's counterfeits galore on Ebay... but the ones I bought were in the Nissan bubble wrap bag, and had the Nissan Logo on the top rim of the pastic covering.... still counterfeit? That's a lot of trouble for a crook to go through...isn't it?

The sub-harness goes between both knock sensors and connects to the main wiring harness.

As far as the counterfeits, who knows... there are people that will go a long way to duplicate packaging and stamp realistic looking part housings. Google for articles on HID bulbs. It is a HUGE market for that... not sure if knock sensors rise to that. Figuring it out probably means cutting open a known genuine one and the one you'd be buying - rendering both unusable.

Heath

Ok Heath, ... so I got another knock sensor (OEM) and also the harnesses. I think I'll replace them too since this is the FOURTH time I am taking the engine apart. I got this down to a science now...(not that it is something to brag about)

My questions:
(1) do the harnesses that I have look like the correct length for a VH41DE??



(2). Is the main engine harness connector supposed to look like this??? I cannot find a detailed diagram of it anywhere....



I bet there is a whole bunch of thick wiring loom and electrical tape to unravel to find those connector ends... anyone else done this on their VH41DE???

(3). One last thing... if I drain the radiator before doing all this again, this should avoid all the spillage of coolant in the valley when I unhook the center coolant Y-pipe... right?

Unless it's different on the Y33, I don' think that's it. The harness on the G50 has two connectors like that that hook to the sensors, and then a larger one that connects to the main harness - on our car it's a 6 pin connector. That connector looks like the one in this picture. From the FSM from your car, there's an 8 pin connector on the Y33.

Heath, I think I found the problem. it must have been making contact with the block and shorting out. upon closer inspection the insulation had just cracked from heat exposure, but I still had continuity, so I decided to repair, rather than replace.



I put three coats of spray on liquid electrical sealant, taped it up, and attached so extra wiring loom to avoid any further contact with the hot surfaces. Oh man, I hope this is the last time I have to get under the plenum.... it's really starting to suck. I inspected the sensors, no physical damage... so I cleaned and reattached them.

That very may well have been it. I'm keeping my fingers crossed that you'll be code free when it's all back together!

Heath

Heath, don't uncross your fingers yet.... I put it all back together.... first few cycles everything is ok... next day... there it is again, P0325!! yes... to me it is P)#@%!!!! I ohm tested the sensors after cleaning them and re-installing them... 0.563 Mega ohm and 0.585 Mega ohm. That is within spec if I converted it right... isn't it? So what is the next step??? Test the wiring from the junction to the ECU? Yank the ECU and have it tested?
How much power and fuel economy is really lost if only one sensor wiring is bad? Can the functioning side still pick up pinging from the opposite bank? I feel like just being lazy about it and just resetting the code every third ignition cycle... It'll be another year before I'm mentally ready to take another crack at this...

Ugg... I'd ohm them at the harness wherever it connects to the main harness. My guess is still that it's the subharness.

Keep in mind that the code has nothing to do with the sensors actually detecting spark knock (pinging). It's just a check to make sure that it's seeing the correct ohms at startup - and there's some speculation that the ECU also uses the sensors to "listen" for normal operating noises - since the ECU will still drop in to the "safe" fuel map even with a resistor hooked up in place of a sensor.

Heath

Ok, I'll check there too... I don't think I have to remove everything to get to the harness junction... Since I don't have the wiring schematic, I'll just try to find two prongs that give me the standard resistance measurement... right? Worst case scenario: What are the chances that the ECU is not putting out the operating 5 volts to the sensor? If the actual sensor is testing ok in terms of Ohms, then it should be sending back 2.5 volts to the ECU, shouldn't it?

ECU failure is pretty rare... not impossible, but rare.

Wiggler wrote:What are the chances that the ECU is not putting out the operating 5 volts to the sensor? If the actual sensor is testing ok in terms of Ohms, then it should be sending back 2.5 volts to the ECU, shouldn't it?

If Nissan used "Pull-Up" resistors that are the same resistance as the knock sensors (500K - 620K ohms), then yes, the knock sensors would "pull down" the 5 volt supply to 2.5 volts.

If Nissan used some other value for the "Pull-Up" resistors, then the knock sensors would "pull down" the voltage to something other than 2.5 volts.

I don't know what value Nissan used for the "Pull-Up" resistors, so can't say what voltage you'd actually measure at the ECM coming from the knock sensors.

However, if there's wiring problem somewhere between the ECM and knock sensors, you'd probably measure either 0 volts (wire shorted to ground somewhere), or 5 volts (open connection somewhere between the ECM and the knock sensor).

Ok Heath & Ski,

Play by play....

Tested ohms at these two circled prongs on the subharness/main engine harness junction, since these were the prongs that tested with any ohms whatsoever.



outer left prong like so....



And middle right prong like nyahhh...



Ohms within spec, right??? So we can conclude the harness is working?

here is ohms with the ignition in the "on" position, motor off.

outer prong:



middle prong.



next, checked voltage from the ECU at the corresponding female ends of the engine harness connector, with ignition in "on" position...




left:


center:


is this voltage within spec??? It's not 5 volts but am I doing something wrong?

Oh... and I almost forgot

continuity check between subharness pin #2 and ECU harness pin #108



continuity check between subharness pin# 4 and ECU harness pin #105



voltage at pin # 108 ignition on engine running position....



voltage at pin # 105 ignition on engine running position...



FSM says these voltages should be between 2.0 and 3.0 volts??? I'm way off unless I'm checking something wrong...

Sorry if I missed it, but have you read the KS at the ECM?
That's the only place that really matters.
Should be about the same at the ECM as the KS.

Read what? Voltage or resistance?

Your resistance measurements on both knock sensors look OK - Which is good news. At least you know that you don't have replace the sensors again!

Wiggler wrote:
next, checked voltage from the ECU at the corresponding female ends of the engine harness connector, with ignition in "on" position...

left:


center:


is this voltage within spec??? It's not 5 volts but am I doing something wrong?

1.3 mV is just 0.0013 volts, which is essentially nothing. All your meter is picking up is just a small amount of random voltage, not the 5 volts which the ECU should be supplying to both of those pins.

So, it looks like you've either got an open connection somewhere between those pins and the ECU, or the ECU itself is screwed.

voltage at pin # 108 ignition on engine running position....



voltage at pin # 105 ignition on engine running position...



FSM says these voltages should be between 2.0 and 3.0 volts??? I'm way off unless I'm checking something wrong...

Again, your meter is just measuring a small amount of random voltage.

Did you measure with the harness connector plugged into the ECM?

Skibane wrote: Did you measure with the harness connector plugged into the ECM?

You mean the ECU harness?? yes.. the harness was plugged in and I managed to stick a wire through the outside of the connector and it was making contact with the metal crimp....
The harness in the engine bay was always plugged in, for the ECU point of testing.

Ski? any other suggestions?