So my car was throwing a P0325 code starting a few months ago. When it does, the timing retards big time and it feels like the car has no power. I can put the pedal to the floor and it accelerates extremely slowly. I took it to a shop and had the knock sensors replaced. It ran fine for a few weeks and recently it started happening again.
If I disconnect the battery for an hour or two the code clears and the car runs fine for a few days. The latest time it happened I took it back to the shop. They say it's also throwing a P0420 catalytic converter code. Shop says it's likely a blocked cat that is causing engine knock, and the P0420 code.
Anyone run into this same situation before? I really don't want to keep throwing money at this damn car, but I don't know enough to be certain of what's causing the problem.
For your P0325, I would go back to your mechanic and ask him to check continuity from the Knock Sensor 1 connector to the ECU.
I would suspect that you have a broken wire. The harness at the block gets very brittle with age.
I will check it out but I don't think it can be wiring and here's why: If I disconnect the battery to reset it the code will not come back for days unless I run the RPM up higher. It can go a week or more if I baby it. If I run it up to 5K rpm the code will come back almost immediately. That doesn't seem consistent with a wiring issue.
That is a fantastic article. I read it and it makes me more certain that it is not a wiring issue. The article says that if the car detects a bad knock sensor (which would happen immediately if the wire was bad) then the car retards the timing. I can drive the car for a week at a time before the code shows up, if I keep the RPM below 2500. If I run it up to 5000 or so then the code will show up and retard the timing within 10 minutes. If the wire was bad I would not be able to drive the car for a week with no CEL.
The article says that if the car detects a bad knock sensor (which would happen immediately if the wire was bad) then the car retards the timing.
Your assumption is invalid. The symptoms of a bad knock sensor usually show up at highway speeds or under a load, that is when the ECU looks for feedback from the sensor not at start up.
Sorry I could not help you, good luck with your car.
Hmm, that makes it more interesting at least. Although when I reset the code I can go highway speeds (75-80mph) without causing the timing to retard, as long as I keep the RPM under 2500ish when accelerating. This will last anywhere from a few days to a week or so. I admit I could totally be wrong but it seems like the car wouldn't be able to go that long under those conditions without a good signal from the knock sensor.
Additionally the knock sensor wouldn't cause the P0420 code, where as a blocked cat may account for both codes. I'm getting the cats "addressed" tomorrow lol. After punching them out and clearing codes the knock sensor code should no longer appear, if the cat was blocked. The cat code will persist.
Once I get the car back I will report on the results... for science.
I would be willing to bet that the shop did not install factory denso knock sensors. If you asked them, they would probably say "they were oem knock sensors". which would be legit, but that's only because one particular brand that makes them is actually called o.e.m. that being said, their junk or anything that's aftermarket when it comes to knock sensors. there are tiny crystals in them that make them super sensitive to engne knock. and the Toyota ecu is tuned to a certain frequency to "listen" to them. Anyways, long story short, I bought those o.e.m. knock sensors for my 2002 gs430 when it had 115k miles on it, and I went in circles because the car kept setting knock codes. I went after the wiring and ohm checked it, which passed. I even made a new wiring harness from knock sensors to ecu and it still set knock codes. it wasn't until I went to lexus of Austin and bought two brand new knock sensors in the pretty red and white boxes. installed them and the car never set knock codes again. that was 10k miles ago.
If your cat is rattling, it can set off both the p0420 and p0325. Keep in mind those knock sensors are like microphones for the ecu. Or possibly have 2 faults. If you are going to punch out your cat for testing purposes, youwill find out if its 2 faults, or 1 triggering both.
I had 2 faults with my 98 GS400. I replaced both knock sensors(oem) and it solved my knock sensor codes. I punched out my left cat and the p0420 went away. I replaced the left cat(aftermarket bolt on) been good ever since. I kept my punched out cat for future diagnosis.
Punching out the cats now. Curious about the wiring issue. If the wiring is cooked or bad near the sensor, can that section be replaced individually? Or is it part of the wiring harness as a whole. I ask because I found a knock sensor harnesses for the Toyota V6s of that year but nothing the V8. Thinking it is not a separate section of wiring like it is on the V6.
