Nissan XTerra Forum banner

1 - 20 of 33 Posts

·
Registered
Joined
·
7 Posts
Discussion Starter #1
What’s up club xterra, I have a 2004 supercharged xterra 4wd. I have a p0328 code, and decided to do the knock sensor relocation. I cleared the code before doing the job, and upon finishing, the code is still there and the truck is still in a limp state as it has been. My assumption is that I do not have a good grounding to the area I mounted it, which is right behind the supercharger, near the firewall.

what would be the best way to diagnose and solve my issue? Is there anyway I could ground the knock sensor directly to the battery? I need as much help as I can get, and any suggestions would be appreciated. Really want to get this truck back to maximum performance. Thank you
 

·
Administrator
2000 Xterra XE 4x4 3.3L AT
Joined
·
9,092 Posts
The harness in question is not the pigtail but the main harness. You replaced the knock sensor and wiring from the main on and the code persists. Need to check everything before that. Find the KS code in the FSM and follow the diagnostic to determine if the harness or connector is at fault.
 

·
Registered
Joined
·
818 Posts
From my understanding it is usually not recommended to relocate t the knock sensor on the SC models. The factory location is the best spot to accurately register knocks and pings and the knock sensor is actually used by the ECM in the SC models. Directly on the engine block between the cylinder banks ensures that there are no gaskets or grommets to dampen the vibrations. Relocation to the intake manifold for example will result in two layers of gaskets between the engine block and the sensor. Relocation to somewhere on the cylinder head also results in gasket interference. If you've used RTV or a gasket sealant on teh upper and lower plenum gaskets (which is NOT recommended) then the signal will be dampened even more. The NA models get away with relocation because they don't actually use the data generated and won't slip into limp mod even if the sensor is bad.

As Racer states,
1) A short or break in the leads or wires.
2) Could be a bad knock sensor
3) Relocation is in a spot that doesn't register correctly.
 

·
Registered
Joined
·
422 Posts
I believe the NA trucks do use the knock sensor signal to limit timing advance, however on a SC model any DTC will put the boost bypass valve in the bypass position as well as limit timing advance. NA engines don’t worry about this because the few degrees of timing dont make that big of an impact. A couple pounds of boost lost will though
 

·
Registered
Joined
·
422 Posts
If you want maximum performance all the time, stick a bolt in the boost bypass valve so it can never go into bypass and you’ll have full boost all the time. Just like a knock sensor relocation, this is not recommended
 

·
Registered
Joined
·
818 Posts
The gen 1 has no automatic spark/ignition timing advance since it's a standard distributor system and is a totally mechanical set up. The only adjustments made by the ECM is for the fuel injectors to adjust the fuel/air mix. Due to the higher compression on the SC models a faulty knock sensor will drop the engine into limp mode to protect the engine. It appears that the main reason for the knock sensor is to detect issues that trigger the SEL, meaning a functioning knock sensor does come in handy for detecting misfires, which are not an uncommon symptom in these vehicles as they age and components go bad. No knock sensor = no misfire detection = no CEL if something is wrong and possible engine damage.

The gen2 switched to coil packs, which allow for the spark timing advance to be controlled by the computer.
 

·
Registered
Joined
·
422 Posts
image.jpg

This is taken directly from the service manual. I know for a fact that the ECM will adjust timing by adjusting the moment that the coils field is energized. Many vehicles with distributors use this to adjust ignition timing which is why properly setting base timing is so critical. Duraspark systems in ford used this all the way back to the 70s. They used it to retard timing during cranking to lighten the load on the starter. I understand that timing can not be wildly dynamic as it can with distributorless ignition but that doesn’t mean there’s no control
 

·
Registered
Joined
·
422 Posts
On a second note, knock sensors are not used for misfire detection. This is done by the crankshaft position sensor detecting fluctuations in engine speed at specific points in rotation. Believe it or not, nissan says the CKP on 1st gens isn’t even used for engine control, only for diagnostics.

image.jpg
 

·
Registered
Joined
·
37 Posts
Mine always went back into limp mode when I had the KS there, but no code. I ended up bolting it to the firewall by the wiper motor. No knock protection but it ran well. Eventually I put it back to stock and it has been running great ever since. Have you verified you've wired it correctly? My friend had his backwards on the harness resulting in a code (he hooked the "ground" wire to the KS instead of the thicker signal wire).

After having owned one of these for along time, and working on many others, I will never do or recommend the relocation again for a SC truck.

Btw you should replace that small line from the SC to the bypass actuator, it looks like it's on borrowed time.

As for the timing, yes the ECU can adjust the timing, it is an electronic distributor with a CPS inside. The only adjustment is the base timing which is what it works off of as a starting point.
 

·
Registered
Joined
·
7 Posts
Discussion Starter #18
Mine always went back into limp mode when I had the KS there, but no code. I ended up bolting it to the firewall by the wiper motor. No knock protection but it ran well. Eventually I put it back to stock and it has been running great ever since. Have you verified you've wired it correctly? My friend had his backwards on the harness resulting in a code (he hooked the "ground" wire to the KS instead of the thicker signal wire).

After having owned one of these for along time, and working on many others, I will never do or recommend the relocation again for a SC truck.

Btw you should replace that small line from the SC to the bypass actuator, it looks like it's on borrowed time.

As for the timing, yes the ECU can adjust the timing, it is an electronic distributor with a CPS inside. The only adjustment is the base timing which is what it works off of as a starting point.
Yes I saw that when I took the picture, thank you for pointing it out. Where could I get one of the lines? All I see are the actuators. Also do you have a picture of where your knock sensor is at? My code is still there, will check the wiring.
 

·
Registered
Joined
·
818 Posts
I guess I stand corrected.

After re-reading your initial post. Did you replace the sensor, or just relocate it?

One of the possible issues you're having is that the new location may be picking up excessive noise from the supercharger. Try moving the location to where 2002XterraSC describes, reset the codes and see if the problem is solved. You could also try to find a location that is actually on the engine block, which is preferable.
 

·
Registered
Joined
·
37 Posts
Yes I saw that when I took the picture, thank you for pointing it out. Where could I get one of the lines? All I see are the actuators. Also do you have a picture of where your knock sensor is at? My code is still there, will check the wiring.
You will need a longer bolt and I had to brush the crust off of the bracket, but it worked. I just matched the line up with a piece of vacuum line at an auto parts store.

75017
 
1 - 20 of 33 Posts
Top