cody o

Hello all! I have a 1994 Pickup DLX 4x4 M/T 22RE that has a throws the CEL with a code 52. According to my Toyota manual, this means the ECM is not receiving a signal from the knock sensor for at least 25 revolutions when the engine is running above 2500 rpm. The light comes on consistently when I rev through 2nd gear for the first time on a trip. Engine temp doesn't effect it. CEL won't come on with transmission in neutral or first gear, no matter how high the rpm. This started a few years ago when I bought the truck. I replaced the knock sensor, which fixed the problem. Recently the problem came back, so I bought a used knock sensor off eBay. It worked fine for a few days, and then went kaput. Three bad knock sensors in a few years. Shot wire. Replaced connector to knock sensor. Re-seated ECM plugs. No fix. Did realize from reading other posts that I had been over-torquing the sensor by quite a bit. There is a small coolant leak that drips onto the sensor. One of the cam rockers has been making a good knock for a couple years. This engine had been run out of oil and rebuilt before I bought it. Also, the cam shaft chewed itself up and was replaced a while back. (Just trying to think of things that might be relevant.)

Anyone have any ideas why my engine keeps going through knock sensors like it's cool?

cody o

I bought a new BWM knock sensor today, which comes with a lifetime warranty.

I still have two questions, if anyone wants to bite:

1) What is the proper torque? I've read between 4.3 and 12 ft*lbs. (I probably put about 50 on that last one.) Is it really that critical to get an exact torque with this sensor?

2) What's causing these sensors to fail, or is it just my bad luck?

shaeff

See quoted message below for proper torque spec. The cam rocker knocking has nothing to do with code 52. Any mechanical noise has nothing to do with code 52, so rule all that out immediately.

Go with 4.3 ft. lbs, as that's almost perfect for the torque spec of 52 in. lbs. It is absolutely critical to get the proper torque spec, the sensors aren't strong like a nut or bolt. Cranking down on them will do as Mike says in the above post. (there is also a very informative thread regarding code 52 linked in my signature)

As for your failing sensors, overtorquing them will do it. Bad luck is always an option. Check your wiring from the connector to the ECU. Verify that there are no shorts to ground in the signal wire. Any short to ground is an immediate code 52.

cody o

Thanks!

I cut one of my bad sensors open with a dremel. What I found was the contact wire was just floating around in there, not really connected to anything. It must have been sheared off like you said. At $150 a pop, I will use a torque wrench this time!

shaeff

No problem, and yeah, a torque wrench is the way to go!

cody o

Installed the new knock sensor last night. Torqued to 52 in-lbs. Everything works great! We'll see if this one lasts...

shaeff

Definitely report back either way.

mapple83

Hey guys, I have to do the same repair. What level of difficulty are we talking about here?

mapple83

One more question that might help me decide if I'm gonna do this myself or take it to a mechanic. How much would replacing a knock sensor cost labor wise at a shop?

cody o

Depends which engine you have. If 3VZE, the knock sensor is on top of the engine and you'll need to remove the upper half of the intake to access it. The 22RE is much easier; remove the panel in the passenger-side wheel well and you'll see it next to the oil filter (oil sensor is there too, so don't get them mixed up). A 1 1/16" socket on a 3' extension will reach it just fine. As stated above, don't over-torque the new sensor or you'll destroy it.

mapple83

Thanks Cody! I've got the same truck as this fella so I'll give it a go!