CEL P325 & 330 Knock Sensors (1 Viewer)

[clownmidget]

Thought I'd start my own thread as I continue to chase this. Started out here (https://forum.ih8mud.com/80-series-...800-3500-rpm-full-throttle-3.html#post7206827) but now it seems I've got more work to do...

Swapped back in the stock MAF and drove truck around for 4 days in mixed driving with no issues. Started a 1300 mile trip yesterday and after about 2 hours of interstate driving with cruise set and loping along at ~70 mph, ~2200 rpms, had the CEL come on. Same old ones - 0325 & 0330 for 1 & 2 knock sensors. Re-set it repeatedly and it kept coming back on. Only "new" clue was when I would re-set it at a gas station stop, on the first re-start of the engine, the engine would rev and not find it's idle. I could kill it, and then restart it and it would behave normally. If I did not kill it, it would keep reving up and down between 2000 rpms and 1200 rpms, never finding its normal idle. It would then drive normally on the interstate but once I'd pull off, it would still not have a normal idle. Still same CEL's for knock sensors.

Both have been pulled, bench tested and reinstalled. Harness is new. Checked connections at MAF, but the harness side is new so everything looks great. It does behave like the MAF is wacky but not sure why this is setting off knock sensors codes. Engine is running very smooth, I went ahead and reset the ECU and put in some high octane fuel but the CEL's came on right away again.

Thought I'd try and clean the MAF with some spray cleaner for it. Maybe clean up the electricl connections. I don't have an EWD with me and really don't want to pull the glove box and crap to check the pins on the ECU.

Any other thoughts or ideas?

Thanks and

 

[OGBeno]

It might be that ECU we discussed...that seems to be the only thing remaining.

You might be able to disconnect the knock sensors, find out the resistence the ECU is looking for and go to Radio Shack and get a couple of resistors, jump it for the trip and attack the issue again when you get back home...

Happy birthday by the way Mike.

 

[landtank]

I'd focus on the distributor.

 

[clownmidget]

I'd focus on the distributor.

not getting any love there. pulled the socket at the distributor, cleaned thoroughly, checked connections, no change. had put a timing light on it before the trip and it was spot on 3-deg TDC. I put it up to ~7-deg TDC and drove it for those 4 days before the trip with no issues, no CEL. Truck behaved normally when setting timing, jumping the pins to put in diagnostic mode, etc. I'll pull the cap when it's light out and check it, but at rebuild (less than 6K miles ago) it got a new distributor cap, rotor, new plug wires, new plugs.

Is there something else specific about the distributor you suspect?

I'm wondering if the knock sensors can bench test fine but behave differently once they have heated up to normal operating temps.

 

[landtank]

I thought that the ECU used the Distributor for setting the IAC circuit. Where you had weird idling and knock codes I was thinking something along the lines of an internal issue. If I remember correctly there is a gap spec for the pick up.

I'll have to go out and get the FSM a do a little reading.

 

[clownmidget]

Ah, ok. For what it's worth now, the CEL code comes on almost immediately now after re-setting it. Doesn't seem to depend on engine temp, running time, etc. I'll check all the harnesses again, and those on the throttle body.

 

[TrickyT]

It might be that ECU we discussed...that seems to be the only thing remaining.

You might be able to disconnect the knock sensors, find out the resistence the ECU is looking for and go to Radio Shack and get a couple of resistors, jump it for the trip and attack the issue again when you get back home...

My educated guess is that this won't work as a bypass for the knock sensors. Unlike the EGR temperature sensor, which is a purely resistive device, the knock sensors are piezoelectric devices and dynamic in nature. You're not going to fool the ECU using resistors as substitutes for the knock sensors.

My guess on the bad fuel economy aspect of the symptoms mentioned in the other thread is that the ECU is running in open loop mode because of the MIL fault.

Mike, you're saying you get the P0325 & P0330 codes regardless of which MAF you run? Also, this is on your turbo'ed rig, right?

 

[alia176]

Subscribed.

 

[clownmidget]

Engine is newly rebuilt 4.6 but not running any turbo. I did realize that it does have the "colder" plugs that I'd run with the turbo. now I'm wondering if it really does have a knock that I'm just not distinguishing and the knock sensors are actually working as they should. The engine runs smoother and quieter than any other 1fz I've been around so maybe I'm just going nuts.

Yes, either MAF same results. Cleaned oem MAF and reset ecu and got cel almost immediately for knock sensors.

 

[landtank]

Had a chance to dig around the FSM.

There is two sensors at play here, the crank sensor and the cam sensor.

They are basically the same type of sensor, the crank sensor is on the crank and the sensor resides in the front of the upper oil pan. The cam sensor resides in the distributor.

The cam sensor basically reports speed and the crank sensor reports crank angle. It's the signal NE2 from the crank sensor that is used to report a misfire.

For either of these sensors to pass the ECU check they need to provide a fluctuating signal. It takes an Oscilloscope to evaluate them during idling to confirm that they are functioning correctly.

Maybe the crank sensor loosened up and with a greater gap between the sensor and index wheel the signal is now sporadic.

 

[clownmidget]

Thanks Rick. I'm betting it won't take much shop time to justify just buying a new crank position sensor.

I'll at least check the harness connections to it. This was another sensor that was re-used after the engine blew.

I'm still suspect of the ECU but that'll have to wait until I find a good deal on the 89661-60262 version.

 

[landtank]

i have both a crank sensor and an ECU that you can use for troubleshooting purposes.

 

[clownmidget]

Rick, I think I'll take you up on your help troubleshooting this. Just finished a little shy of 1500 miles total and trip was a little too exciting for me in terms of 80 ownership.

I did pull the distributor and crank sensor, cleaned everything up, nothing looked out of place. I put a small can (4-cylinder size) of SeaFoam in the fuel tank and topped it off with premium before heading to WV. No change, CEL came on within a few minutes of driving.

I did have my oil pressure drop all the way to not even registering on the dash gauge during this trip. I don't know if this can be attributed to the SeaFoam or not, but that was the only variable. I changed the oil out with new 10W40 dino and a new filter and it returned to normal pressure levels.

On a side note, I blew a braided stainless steel brake line - one going from axle housing to caliper on DS -while going down an exit ramp. Not Fun!!! This almost stopped us dead in the water. It was 4 PM on Friday and the soonest I was going to be able to get one was Weds, Jan 4th. Luckily I was able to find a local hydraulic line shop that repaired it. I think I'd advise folks traveling extensively to carry a spare brake line or two.

 

[landtank]

I'm heading out to Buffalo in a couple of weeks if that will work or I can ship things out to you when I get back on Friday.

I personally hate SS brake lines and had an issue with one up in the mountains in NC. I'd go OEM of the extended length for a replacement.

 

[clownmidget]

Ok, thanks to the generosity of Rick I was able to swap in a known good ECU, knock sensors and crank position sensor from a 1997.

The ECU from Rick was a 89661-60261. The one in my truck, from a salvage yard installed by the previous owner was a 89661-60260.

The knock sensors on mine had clear markings on the sides. Looks like a "61" in large type and then a "522" in smaller type beneath that and then a "M" mark. Pretty sure that they aren't Toyota OEM. The one's from Rick had no marks at all.

Then the crank position sensor on mine had the insulated ground stripped away from the last 1-2 inches right at the sensor. Not sure how that would affect the actual function of the sensor since it sounds like that shielding just protects the sensor from picking up random RF signals from other things in the engine bay. At any rate, the one from Rick had a nice rubber boot covering up all of that.

So, went through 4 start cycles and drove it ~ 5 miles so far with engine RPM's from 2-4K and no CEL. Will take it for a longer trip and then start trying to figure out what is truly bad.

 

[TrickyT]

My $0.02 is that those knock sensors don't play well with the ECU.

The missing 2" of shielding should not have a significant effect on the CPS for just the reason you say. And that sensor is already physically protected by a metal shield which will also serve as a partial RF shield.

If no CEL after several days put that old ECU back in and see what happens.

 

[alia176]

I was under the impression that knock sensors are simple piezoelectric devices and made generically. It'd be interesting to find out the root cause of these two codes? I can see Rick's "knock sensor investigation kit" being passed around the Mud community, LOL!

 

[kidglove13]

I have an old knock I pulled from my 94 and it has an M on it and a 61 like yours
but has 452 stamped on it and also has toyota stamped on it as well

 

[landtank]

I was under the impression that knock sensors are simple piezoelectric devices and made generically. It'd be interesting to find out the root cause of these two codes? I can see Rick's "knock sensor investigation kit" being passed around the Mud community, LOL!

Like any sensor I would expect them to have an operating range and sensitivity value.

If the CEL is gone they would be my guess as well.

 

[TrickyT]

I was under the impression that knock sensors are simple piezoelectric devices and made generically. It'd be interesting to find out the root cause of these two codes? I can see Rick's "knock sensor investigation kit" being passed around the Mud community, LOL!

I'm only guessing that the knock sensors aren't the right ones for the salvage yard ECU. For one thing, both were throwing a code and I think it unlikely that both sensors were bad.

To support the idea that not all knock sensors are created equal, here's a quote from this document: http://www.wellsve.com/sft503/counterp_v4_i4_2000.pdf

Many sensors look alike, physically. But the sensor is matched to the engine and the PCM. Since all engines vibrate, the engineers must spec the knock sensor so that it doesn’t react to “normal” vibration and only reacts to knocking. The wrong sensor, even though it fits, may not work properly because it won’t correctly identify normal and knocking vibration.

And here's a document especially for the control systems theorist in you, Ash: www.ti.com/lit/ds/symlink/tpic8101.pdf. It's the spec sheet for a TI chip that is used to interface to knock sensors. Both the sensor gain and center frequency of the band-pass filter are programmable so that they can be tuned to the specs for the sensors and the needs of the engine designers.