I've got an 88 4Runner with a 3.0. It's throwing a code 52 and running like complete crap. I'm trying to diagnosis what the problem is and I am getting .2 volts ac at the pig tail connector to the knock sensor at idle. Is there anyway to test the ecu to see if that's the problem. Thanks

 

Also the engine runs bad/no power/won't rev in neutral/ regardless if the check engine light is on from code 52 or not. Is this a symptom of a bad knock sensor or something else. I'm going to check the voltage at sensor tomorrow while knocking on the block to see what the reading is.

 

Code 52 is the ECU signaling that it cannot see the knock sensor.
Its rare the knock sensor has gone bad and is most likely the pigtail
has a break and needs replacement.
The mini-coax that connects to the pigtail runs over to the diagnostic
port and then on through the firewall to the ECU.
Look for bad spots in your harness.
Make sure the diagnostic port is not filled with crud that could short the connections.

Its running like crap because it is in limp mode.

 

Ok, thank you I didn't know if the engine should still run bad even with the check engine light off? If some thing else could be causing the engine to run bad as well as the knock sensor code.