slow-mo

When a diagnostic trouble code is set, most people assume, without testing, that whichever sensor that threw the code has failed and that is what's causing the trouble code.

What is in reality is the the computer detects a circuit fault or a system fault. The circuit or system will consist of (in this case) the sensor, the sensor connector, the wiring harness including all of the connectors leading back to the computer and the computer itself.

A diagnosis of the whole circuit is needed to determine what triggered the fault code or what is continuing to trigger the fault code.

Since the knock sensor detects frequency, yet converts that frequency into voltage for the computer to monitor, at least a graphing multimeter capable of recording the voltage and time is needed to accurately diagnose the fault. At best, an automotive oscilloscope. But since most people don't have these, the first thing that is done is to replace parts.

Mauk

Thanks for all the great info guys. I really appreciate it.

I was going to take it to a mechanic the other day and have them do a diagnostic on it but I noticed my brakes are like super touchy and even lock up when I apply light pressure.

would I need to bleed them? the truck has been sitting for a while also

Mauk

Ok so i got a diagnostic done an the guy said hes never seen this problem before..
there is a knock that is so small you cant hear it but the knock sensor is reading it and throwing the code 52 anyways he said that i need to rebuild the engine.. great.

what do you guys think??

combatcarl

Search "code 52 yotatech" on google. It's a code that it kicks when the ECU loses communication with the KS. The KS works by advancing timing until it begins to detect a knock, then retards until it goes away. It repeats that cycle continuously while the engine is running, many times a second. In other words, it's invisible. Until it can't see the KS signal. Then it kicks the 52 code. The issue lies between your ECU and KS. I will bet that your engine doesn't need a rebuild. So with some reading, troubleshooting and a relatively cheap length of shielded wire, you'll be good to go. Or a $1500+ rebuild, and the same code 52 still.

scope103

You need to find a new "guy" to do your diagnostics. CombatCarl has it right (good explanation, too). Code 52 has nothing to do with whether your engine is knocking. Code 52 means your ECU can't tell whether your engine is knocking (so it retards the timing to save the engine, and the engine runs like crap).

It's probably not the knock sensor itself, rather a wiring issue. That's what you need to work on, not an engine rebuild.

Mauk

thanks! thats what my gut feeling says..
ive looked at the shielded wire post but not too in depth. but i will now

shdwrdr

I am having the same issue! I have a '91 4Runner with the 3.0 V6 that is not the original engine. I replaced the KS and the pigtail. Got it back together and timed the engine and took it for a test drive and the check engine light came back on and checked the codes and got 43(starter signal) and 52. Cleared codes and just 52 came back. The light doesn't come on till the engine is accelerated. When I had the plenium off two of the passages were dirty. So I do believe that its electrical or dirty intake or something along those lines. What would be the best way to check the wiring between the KS and ECM? I also seen that someone mentioned doing a Seafoam treatment. So what is the proper way to do that? I was also going to fill the tank and add octane booster or should I add Seafoam instead?

I am not good at all at working electrical issues so any ideas would be greatly appreciated.

scope103

Correct; you don't get code 52 until you're at the right place in the rpm range.

Code 52 means the ECU has "lost touch" with the knock sensor. It has nothing to do with dirty passages or Seafoam or octane booster. (Do we need to say this again? It has NOTHING TO DO WITH WHETHER YOUR ENGINE IS KNOCKING.)

It's almost certainly a wiring problem. If you replaced the pigtail (with a NEW one, I assume), then you'll need to check the wiring from the connector back to the ECU. For starters, disconnect the KNK connection at the ECU, and "ohm out" the signal wire and shield back to the connector.

shdwrdr

Ok, bear with me, this is the direction I was looking for, THANK YOU. You may have to dumb it down for me some. So a signal wire would be to disconnect the pigtail(yes it is a new one) also and connect a wire to it and come around to the KNK and connect the ohm meter onto the wires, in line, to test the wire? Will I have to hunt thru the connector to find the right terminal for the which one is the KS? Am I reading you correctly?

scope103

All answers are in The Good Book.
http://personal.utulsa.edu/~nathan-b...86troubles.pdf

Yes. The knock "wire" is shielded. You want to (at a minimum) test that the signal wire isn't broken, that the shield isn't broken, and that the signal wire isn't shorted to ground or the shield.

shdwrdr

I disconnected the KS at the pigtail and the wrap on the wire was brittle so I pealed it back and the outside insulation was gone for about 1/4 inch and wire seem a bit broken up and green with corrosion on the. I think this might be the issue. I did check the resistance but read ok. I don't believe the reading with that kind of damage. Just got to figure out how to repair it. Any ideas? The connector has two connection points in it and it seems like it has and inner wire then insulation then the outer wire cluster then the outer insulation. Do they make a piece to fix this?

scope103

It's "fairly ordinary" shielded wire. Your cable TV comes in over RG-59; that's a little fatter than you need (designed for high frequencies), but cheap and common. Or you can use microphone cable.

The hard part is attaching it all to the connector; I can't help you there.

shdwrdr

Thanks for the info. I will see what I can come up with and let know how it turns out.

Gevo

Go to post 217 at the link. I recently did this job myself. use my research, I have a link there for the wire i bought from ebay. it's working great.
https://www.yotatech.com/forums/f199...5/index11.html

shdwrdr

Well I must have something else going on because I completely replaced the wire to the knock sensor and took it for a ride and a half mile down the road the check engine light came on again. Before I couldn't get no more than 300 feet and it would come on. The timing is on and it is idling at only 600rpm. I believe it should be idling at 800rpm and there seems to be a miss or chugging, if you will. So at this point I believe that there is something causing it to throw a code for the knock sensor. So any ideas?