Check Engine Code 52!!!

[U2502]

So I have been plagued with Check engine light problems on my 1995 Corolla DX Wagon. Every time it has been code 52 which is for the knock sensor. I replaced the knock sensor and the Oxygen sensor (thought it was a code 25 at first) and after a month of the light not coming on, it has come on again with the code 52. I am stumped and so is my mechanic. The other problem that I have been having is that every so often, when I am stopped at a stoplight the engine will briefly idle really really low and then go back to normal. The whole process lasts about 2 seconds. Are these problems related? What is the next thing that I should replace? Thanks so much for your help, I really appreciate it!

--micah

[94_Rolla_Guy]

the idleing thing might be caused by a dirty throttle body, the other thing may be the brake booster when i push on my brakes to a certain point the engine will slow down, haven't been able to figure it out but its definately the brake causing this

[U2502]

Thanks so much for the quick reply, any ideas about the Code 52 coming up even after I have replaced the Knock and O2 sensors?

--micah

[neophile_17]

Hey,

Can you or your mechanic test the knock sensor to verify it's functionality? The difference being that you could have another problem which causes the knock sensor to fail or you could have a loose wire or just bought a bad knock sensor. The latter two being annoying but much cheaper and fairly easy to fix. Try cleaning and putting dielectric grease on the connectors and making sure that they are tight.

Alternatively you can look into replacing the knock sensor with a resistor that tells the computer everything is fine even if it isn't. This is done on several other cars for performance when the computer is over-zealous about about taking out timing for knock. But it also means that your engine will no longer have knock-protection so do your homework.

Also your low idling could be caused by the computer getting a knock signal as it will adjust timing and/or fuel to avoid knocking. I think that it is quite likely that the two are linked.

Hope this helps.

~neophile_17

[U2502]

Thanks Neophile, I was going to have my mechanic change the wire that hooks into the knock sensor next. I will also have him put the multimeter to the sensor to see if he is getting an output voltage. Hopefully the new wire will do the trick. I will post an update next week.


--micah