midiwall

I thought I'd babble a bit for the sake of folks doing searches, to generally document an interesting little "issue", and to rant a bit about Toyota's 3.4L engine design.


So, let's get to know the P0330 code (and it's close cousin P0325)- the "official" word is that this is a "Knock Sensor 2 Circuit Malfunction" (the P0325 is the same but it's KS 1 over in Bank 1). I've been throwing this code since shortly after installing my supercharger, and man, it was "fun" to deal with.

For the longest time, I figured that I'd pinched a wire when I put the S/C on since the code talked about the "circuit" and not so much as the sensor being out of range. And, given that the truck seemed to be running "fine" (no signs of ping) I basically ignored it.

Well, a couple of times I pulled the S/C, opened up the service manual and hunted down the harness. But (and this is where the rant starts) I stopped short of getting right to the sensors 'cause they're _under_ the intake manifold. Ummm, HUH? I'm no "engine guy" but it really confuses me why Toyota would put the knock sensors in such a weird place. This means that to get to them, you have to pull the plenum, drain coolant down past the top of the engine, and pull the intake manifold. That's gonna cost ya' in coolant, and a couple of "should be replaced" gaskets.

Oh.. it also means that you get to pull the fuel rails (read, "spilled fuel"), the injectors, and one of the heater hoses (read, "leaks after reassembly").

(click for a larger pic)
the knock sensors are circled in green in the larger pic:


<rant off> Anyway... I let this go for a while and just got used to the amber light for illumination. (I should point out that I could always clear the code, but it'd be back "in short order" - more later).


Well, then it came time to renew my license tabs. And... yeup, I was up for emissions testing. And... yeup, the state of WA won't pass a vehicle that's showing a CEL. CRAP - okay, time to really get into this and... I'm short on time. My tabs expired in 4 days.

I talked to a local master tech for a while (thanks again Double D!) and he gave me the confidence that I could pull the engine apart enough to figure this out. A side note here is that I had never really taken a wrench to my truck _at all_ until just about 18 months ago, so this was pretty new territory for me.

I pulled the S/C, pulled the fuel rails, injectors, that heater hose and finally the manifiold. Here's a bit taller of a shot of how much came off and got pushed out of the way:

(click for a larger pic)


Another side note - take the hood off, it's SOOOOO much easier!


With the knock sensors exposed, and the short harness out, it was time to start testing.

(harness pic)


First, continuity tested fine from one end of the harness to the other, twisting/turning/etc. didn't disrupt anything. So outside of the harness being pretty brittle (the end connectors and the wire casing itself) things where okay there.

Next stop was to pull both knock sensors and test them. The official procedure in the FSM only checks for a short - there's no safe test to see if the sensor is actually good. Both were fine, so... back in they went. BUT! One thing I did was to swap the sensors, that way, if I throw a code again, then I'll know more about if it's a sensor or a harness issue. e.g., if a code comes back as P0330, then since I swapped the sensor, I know it must be a harness. If the code changes to P0325, then I know it must be the sensor since I swapped them. Cool huh?

Oh, and "why didn't I just replace the sensor?" because they're $120 from Toyota (no time to wait), and $258 from Schucks (OUCH!) and I wasn't sure that was the problem.

Onward!

On the way back together, I made a pit stop at the intake gaskets:


At the right and left ends of each of them are the coolant channels, and you can see the condition of the inner-rim gasket material. Given that Schucks wanted _$165_ !!! for a new set (hahahahh!) I checked with The Master Toyota Dude and he confirmed that I should be fine shooting some Permatex Red around the rims on both sides.

That done... I put it all back together.

Double check, triple check, turn the key... vrooom! (this was a cool moment for me. I know it's not like I had the heads off, but... )

Okay... test drive! Out of the driveway, down the road and... BLINK! CEL.... pull the code..... P0325. We have a winner! That pretty much told me that it was a sensor, but just to be sure I pulled the short harness apart and wired ECU Input 1 -> Sensor 2, then ECU Input 2 -> Sensor 1. That should have made P0330 come back, and it did.

Okay, so now I know it was a sensor, and even which one! But, I didn't want to pull the manifold back off, and I couldn't keep throwing codes to pass emissions testing. So... I hacked it.

At the harness, I wired the #1 and #2 inputs together, then wired them to the #2 sensor (the good one). That means that the ECU will be happy in getting reports at both input leads, even though it's from the same sensor.

Yes, I know this isn't a long-term fix, but we're talking emissions testing, and if I really did start knocking, I'm running a piggyback computer that I can use to retard the timing.

Clear the code one more time, back on the road and... VOILA! SUCCESS!!

No codes! No codes! No codes!


Whoa... wait... WHAT'S ALL THIS NEW POWER????

Oh man... this was a HUGE learning spot for me. When I started tossing this code, I knew that the ECU would do "something" to handle a knock sensor going out, but I thought that it's safemode response would be to leave the timing alone. Nope. uh-huh. nadda.

It drops the engine into MAXIMUM RETARD! ARGGGGHHHHHHHHHH!!!!!!!!!

Sure enough, a trip back into the FSM confirms this. Basically, the code will get thrown if the engine doesn't hear from a knock sensor in 3 RPM cycles from 1700-3000rpm. And when it throws the code it responds with maximum spark retard.

Well dang man! That certainly explains the lousy power I've been having from the ground up! I still had plenty of power at WOT, but the "midrange fun" had been missing for a while!

ARRRGH! (but) YAYAYYAYYAYAYAYAYAYAYAYYA!!!!!!!!!!!!!

So in a nutshell - If you ever throw a P0325/P0330, pay attention to it.


Fun stuff...

From the "Wow..." pic department... Does anyone remember when their engine was this shiny? (this is the underside of the manifold)



And from the hindsight department...

• Drain more coolant than you think you'll have to. I didn't and ended up with coolant puddled to the bottom of the sensors in the middle of the "V". Wet/Dry ShopVac's are handy.
• Read the FSM and learn that there's a method for testing the sensors without having to pull the manifold. Do this BEFORE you pull the manifold.
• If you're following the FSM test method, turn off the engine before swapping the jumpers. It'll save you having your arm twitching for an hour after getting zapped by being too close to a plug wire.
• The ECU's safemode is FULL RETARD - not "leave it alone!".
• The knock sensors really are under the intake manifold on a 3.4L.
• You can reuse the intake gasket, but have some Permatext Red on hand.

WATRD

Subtitled as "Midiwall's Odyssey". A fine bit of automotive exploration.

MAIS0N

Midiwall, UR the MAN!!! I developed this issue a couple of months back and just got around to dealing with it. Thanks for taking the time to write it up.

One question, where do you think the best place would be to splice the sensor inputs together? I don't want to do too much teardown just yet.

MAIS0N

Thought I'd update my reply. I spliced the wires together at the ECU and it worked perfectly! All the s/c power came back. Good write up, thanks.

99SC4Runner

Midiwall,

Can you post up the pictures that were in your post? I have the P0325 code on my 99 4Runner, and would like to troubleshoot it. I did fill up with reg unleaded on the last tank though, so I was hoping that if I go back to super unleaded that it might go away?

Thanks,
Doug

toytech76

There is a reason why they use 2 sensors and not one. You can damage your engine by splicing the 2 circuits together, especially if you are running a S/C. Running both circuits on one sensor bank won't let the ecu to pick up pinging on the bank you bypassed therefor possibly causing damage, especially with forced induction. This is something you shouldnt half ass, fix the problem the right way. Repairs like this keep me and other technicians gainfully employed when it gets towed in due to major engine damage and you get a $5000 bill for engine rebuild instead of the $120 for a sensor

99SC4Runner

toytech76,

I noticed in your signature, it says you have an "added 1/2" spacer to your front 3" Revtek lift. Where did you get the 1/2" spacer from? I need to do that to my 99 4Runner.

Thanks,
Doug

toytech76

I had some hardened spacers from something laying around the shop that I used. If I had any extras, I would send them to you. You might be able to go to a hardware store and see if they have any. They will look like very thick washers. The inside should be just big enough to slide over the top studs and not too big around on the outside diameter. You may need to get 1/4 spacers and stack them on each other. Get 3 per strut if you can find 1/2" or 6 per side if you can only find 1/4".

jrock

now its my turn! Got the P0330 bank2 circuit code. Interestingly, it showed up after tuning my MAP B of FTC1 or timing map which seemed to finally get dialed in,...eliminated knock. 4runner seems to have been running good too, although obd shows 30 degress timing. is that pretty serious?

So ill pull off the s/c and replace the wiring harness since that seems to be the culprit 99% of the time aye...

MAIS0N

Final update...

I have been running the splice for 3 years now on a s/c'ed engine. No ill effects. Finally got around to fixing it after the other one went out. Perfect timing actually since I was well overdue for a timing belt and waterpump. Did it all on the same teardown.

This is just for info. I don't necessarily advocate this fix. There is probably a risk factor involved. The $120 figure is per sensor, roughly. I was quoted $180 a couple of other places.

The teardown is fairly involved and there are some gaskets to buy ($$) also as the intake manifold has to come off. For me it was worth it to wait until the second sensor went bad and do it all in one shot vs. doing it twice. You make the call!

For the record, I replaced the sensor wire harness as well. It checked out OK for continuity but the plastic sensor connectors were getting crispy from the heat.

Jakemir

MAISON, can you explain where the wires are located for the Knock sensors. I have the 3.4 liter Supercharger, and have code P0330 also. I am not able to locate any of the wires for the two knock sensors. I understand the sensors are under the intake, but where do the wires go from there. Pictures would be most helpful. none of the pictures above are viewable. Thanks

jrock

This should help ya...

http://www.ultimateyota.com/index.ph...6&topic=8429.0

Notice that my harness connected on top, behind timing belt cover to sub harness whereas the other guys wrapped down below lower left.

MAIS0N

Here are some pics from my last teardown.

http://i20.photobucket.com/albums/b2...aEngine001.jpg
http://i20.photobucket.com/albums/b2...aEngine002.jpg
http://i20.photobucket.com/albums/b2...aEngine003.jpg
http://i20.photobucket.com/albums/b2...aEngine004.jpg
http://i20.photobucket.com/albums/b2...aEngine005.jpg
http://i20.photobucket.com/albums/b2...aEngine006.jpg

Hope that helps,
-Pat

Jakemir

Thanks JROCK and MAISON, the pictures helped a great deal. Temporarily wired both the grey and black connector wires to the working grey wire on circuit 1. This should get me by until I attempt the great project of removing the intake to replace the harness (P# 82219-34010). Not looking forward to it. Thanks again.

jrock

replacing the wire harness did not solve my codes, so im going to wire up a chevy knock sensor into the wire harness 2maro. Im going to place the knock sensor into an old stock exhaust header heat shield thread...guys on CT have done this...only cost $30. I hope it works cuz my rig runs like ass right now!

**update** I mounted up the GM sensor to a nut which was welded to a manifold bolt that used to hold my stock header heat shield in place...disconnected the stock knock wire harness. Connected new GM wire harness(1 wire) to some coaxial cable a toy mech gave me(3 wire-1posi, 1neg, 1ground) just connected both to the 1 wire from harness and soddered. wrapped ground around a bolt. Spliced other 2 ends into knock sensor wires at ecu.

several runs beyond 3krpm=no CEL!!!!!!

macguyver1118

Hello All,

New to this forum but long time Toyota owner.

2001 Taco 3.4 SC all stock. I won't waste your time by repeating everything in this thread but I have this PO330 code. Tried this splice fix (short term!) and the code 330 code went away and was immediately replace with a PO100 MAF Circuit error????? Troubleshot this but all is good. Took my splice back to normal and problem just reversed itself again..no PO100 but PO330 is back??? Triple checked my splice and MAF Circuit but all is good. How could this possibly create a completely seperate problem like this? I am pretty tech savvy so throw it at me. Thanks to all!

MAIS0N

After fighting with this code for a long time I finally came to the conclusion that the knock sensors generally don't go bad. Sometimes the harness goes bad but I found out in my case that it seems to be that the sensors were picking up an actual knock.

I came to this conclusion because I later started having some very wierd pre-ignition type symptoms which I think the knock sensors were detecting before it became otherwise obvious. I won't go into all the gory details because the fix is relatively inexpensive and easy. In a nutshell, it has to do with the wasted spark configuation of the ignition system and bad spark plug wires. I think I posted something about it a while back with more detail but I don't have time to go look right now.

So my suggestion would be this: Replace all your spark plug wires AND spark plugs. Check the boots on the spark plug ends of the coils for any carbon trails also and clean them up if necessary but usually the problem is on the wire side rather than the coil side. (Plus coils are a lot more $$).

Pretty much what seemed to be causing the knock sensor codes was carbon trails alongside the spark plugs. Carbon trails allowed the ignition pulse to bypass the spark plug intermittently causing a misfire. The unburnt fuel in the cylinder then went bang later when it wasn't supposed to - right before and/or as the exhaust valve was opening. This causes a difficult to detect knock but the knock sensors "hear" it and throw a code. Mine went on for a long time before it became obvious enough that I tracked it down to plug wires.

So try that. It sets you back about $50 or so but you might be suprised. Just make sure you do both plugs & wires at the same time. Those carbon trails are hard to see and if there is any left over on either the plugs or the plug wire boots it will come back & you get to start all over.

D33Ray

p0330 was the code diagnosed. i replaced both knock sensors plus both air/fuel ratio sensors. but the CEL is still on.. please help im $900 in parts thus far still the light remains on. i also reset the CEL by removing the battery cables. Whats Next!!!!

MAIS0N

Spark plugs & wires. Coils next if that doesn't fix it.

slacker

iTrader: (1)

for the coin you spent , I would just do a engine re & re


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