DrCreosote

I have a 1990 4Runner with a 3VZE in it and my Check Engine Light came on recently. I pulled the codes and got a 12 and a 52, so I know it is the knock sensor. Because it is going to be some time before I can fix it properly, probably 6 weeks or so, I did 'that thing' and attached an knock sensor to the engine lifting hook. That cured the 12, but the 52 is still there and now I have some questions about it.

1- Since plugging it into this other unit cleared the code 12, but not the code 52, can I safely assume that both the wiring and the computer are receiving a signal and operating properly?

My understanding of the process is that the code 12 is generated when the unit is disconnected and the code 52 is generated when an unacceptable sound wave is received and that makes sense given that it is much more exposed to external noises and the flexing of the engine hook and much more.

2- With code 12 gone, the engine runs quite a bit better even though code 52 is still present. I read that the engine is in a fail-safe mode to protect it from further damage. Can I safely assume that continuing to drive it will not hurt it, but just give me lousy mileage?

3- Looking at the diagrams and the apparent amount of work involved, this is going to take some time. I'm guessing several hours to get it apart and at least that much to put it back together. I am curious how much has to actually be done. I know I'll have to remove the fuel rails and there are water lines involved as well as the typical army of vacuum lines. I was thinking I could use some spring clamps to hold the timing belt to the pullys (the timing belt is only 6 months old.) Will I need to take the front of the engine apart as well, or can I do this job without doing that?

4- Finally, I need to know if it is even possible to get the correct wire for this. Mine uses a round connector and all I can find for this year is a squarish connector. I would prefer to have the right stuff, but I can make it if I need to. If anyone knows a part number for the right wire and could tell me, that would be really awesome.

Thanks for the help.

scope103

What makes you think code 12 has anything to do with the knock sensor?
http://personal.utulsa.edu/~nathan-b...85diagnosi.pdf

You just bumped into something in the wiring, and that cured the 12. Let's hope it's a "long-term" cure.

With code 52, the timing is way retarded to avoid the risk of pre-detonation (this is not the same as "fail-safe" mode, but that doesn't matter). With significantly retarded timing you will have poor gas mileage, very poor throttle response, and bad emissions. You're not going to have fun driving it, but it probably won't wreck it.

You don't have to remove the heads, so you don't have to do anything to the timing belt or anything else in the front of the motor. You will have to remove at least two of the fuel lines, so you will need at least 8 crush washers. A dealer item, and cheaper than mud. Don't let anyone tell you you can reuse the crush washers; do you really want to have a fuel leak under the plenum, where you can't even see it?

Here's the part number: 82219‑35010. Here's the part: http://www.toyotapartsoverstock.com/...221935010.html

(Hint: using the search function right on this site has some pluses and minuses. But using plain ole google with yotatech:pigtail part number pulled up the right entry as the first one!)

Last, you didn't really think 'that thing' was going to work, did you?

DrCreosote

Thank you. I had doubts that it would work, but it was cheap and fast, so I gave it a shot. Even at that, I had no intention of leaving it that way, just to get me through until I have more time. When my work downtime starts in a few weeks, I'll have ample time to make the proper repair.

DrCreosote

Just an update. I had a look at the wire and connector coming up from the sensor and cleaned them with some contact cleaner and a tiny wire brush and re-assembled it. After I cleared the codes, I still get a code 52, but no code 12, so at least I don't have to rely on the external sensor setup now.

I am curious what the code 52 actually means though. Does it mean there is no signal coming through, or not an appropriate signal coming through? Should I be checking other things as well?

scope103

Code 12 has nothing to do with the knock sensor (that's why I provided the link). Let's just hope it was an intermittent glitch, and stays away.

the code means it can't read a valid signal from the knock sensor. (It has no particular way to distinguish between "no" and "inappropriate" signal, even if that difference meant anything.) This is significant because the sensor produces a small signal in a very noisy environment. The wiring to the sensor is shielded (so replacing it with a piece of wire out of your junk box is a waste of time.)

Since you haven't removed the intake manifold, the connector you're talking about is between the "pigtail" and the rest of the harness. The pigtail is in a hellish environment and often fails. While code 52 can be caused by lots of things, a bad pigtail is the most likely culprit. Good news: it's less than $10. Bad news: you have to remove the intake manifold to get to it.

Last, "congrats" on understanding code 52 well enough to NOT ask whether it means the engine is knocking.