Following this thread and trying to learn about new to me 93 4runner. I tested it today and it has a 52, my issue is that it is running rich and not sure how this corelates with the knock sensor. Is it possible the sensor is throwing something else off causing it to run rich? The motor was rebuilt all wires,plugs cap throttle intake etc, was replaced. Thanks for any help

 

Welcome to YotaTech.

Code 52 is accompanied by your rig running with the ignition retarded. Other than that, it should have no affect on running "rich."

I'm going to guess that your rebuild did not include replacement of the Knock Sensor pigtail. I'd start there.

 

The Toyota FSM states that a code 52 is a circuit break or short somewhere. Or said plainly, there's no signal from the knock sensor. This means it's a wiring issue, not an engine performance issue. Code 53 is a knock detected. Grab an ohm meter and check all your wiring, It's probably the wiring harness off of the knock sensor. If you can't find it, you can always be "lazy" and just replace the whole knock sensor and wiring harness, but makes sure to buy Toyota OEM. The aftermarket ones are spotty at best.

Code 52s are some of the most frustrating codes on a toyota because it feels like a gohst and can be extremely difficult to find because its usually a loose connection or small wiring break. If I remember correctly the voltage range for a working knock sensor is rather small so small breaks will cause it. You get all sorts of performance issues because if the computer senses a 52 it runs the engine in what I'll call "safety mode" which fully retards the timing to avoid any potential damage, because it doesn't know whats going on.

 

I just had a similar problem with my 91 3vze. Replaced knock sensor, pigtail, and then all wiring back to ecu. I used the original wire from the wiring harness to connect my new shielded wire to the ecu.

I was still getting error code 52. I then de-pinned the knock sensor wire from the ecu plug/connector and checked to see if the wire was landing on the pin inside the ecu body. Sure enough, the wire connection was loose/not great on the ecu pin.

I went to a salvage yard and found a donor vehicle and got a “new” used ecu plug with all the wires attached. Chopped the plug with about 4” of wire sticking out if it. I then de-pinned the knock sensor wire from the plug and replaced my bad knock sensor wire end with the new wire end (soldered it on), shoved the new wire end into the ecu plug and put the plug back into the ecu. Fired up the engine and the code 52 was gone finally!

moral of the story - de-pin the knock sensor wire from your plug connector and check to see if the wire is making a good connection to the ecu pin. De-pinning requires a special tool available at Napa and a special skill I learned from watching a few YouTube videos on how to de-pin a Toyota ecu plug. But this was the only connection I hadn’t replaced, and it was the fix for my knock sensor code 52.