help, understanding knock sensor error 22?

[Guest]

My 97' legacy rs has had a knock sensor error come on and off since I've had it (about a year).

It has some relation to over heating, only really happens driving in the city or going quite slow. I can get the CEL to go away if I have the heater on full blast. even that has it's limits if I'm driving slow enough.

I replaced the thermostat about a month ago and it seems to help a bit but not really. The thermostat was effectively gone...only the outer hoop of metal and its rubber ring were left. The old coolant was very rusty, when I replaced it there was that air in the matrix sound but I seem to have bled that all out using the hill trick.

I'm about to get the knock sensor replaced, hadn't done this previously because it reads up to be such a mission to replace and I think I'd have given up before getting the intercooler back on.

[Wiretap]

if its only overheating going slow, I expect your radiator fans (or one of them) are not functional, knock sensor code will come up if the engine is knocking severely, plenty feasible if the engine is running hot.

[Guest]

ok. i have seen them functioning, pretty sure it was both.

when the thermostat was missing the radiator seldom got that hot. I haven't checked it since replacing

[Wiretap]

 mint said:

ok. i have seen them functioning, pretty sure it was both.

when the thermostat was missing the radiator seldom got that hot. I haven't checked it since replacing

try bridging out your heater core, my GTS2 had random overheating issues, was due to a blocked heater core.

[Guest]

I think i follow,

so i have the coolant flowing straight into into the radiator?

[Guest]

The heater is still heating the cabin, which is awful in this weather

[Wiretap]

 mint said:

I think i follow,

so i have the coolant flowing straight into into the radiator?

bridging it out is to put a pipe that joins the two heater core metal-lines together on the block side, excluding the heater core from the circuit without plugging anything. you could have a partial blockage that is simply 'slowing things down' enough for the thermostat to close.

[Guest]

That sounds do-able for my skills, cheers.

Is it a good idea to get a pressure test done on the radiator?

[Wiretap]

 mint said:

That sounds do-able for my skills, cheers.

Is it a good idea to get a pressure test done on the radiator?

Only if you suspect it leaking, really. otherwise just change the cap, but that doesnt sound like what it is.

[log1call]

The motor will knock if it's getting too hot so fix the cooling system first.

Since the coolant was grotty you may need a new water-pump, they can loose their impellers to corrosion. You should also take the radiator out and take it to a radiator specialist and have them take the hot end tank off because they can get filled with muck which slows the flow and cooling. The heater core is fairly easy to flush with a garden hose.

[Guest boostin]

But a knock sensor code doesn't mean it has sensed knock. It means the sensor resistance is out of spec. You'll need to check the resistance of the wire back to the ECU which should be 0.5 Ohms or less. If thats ok then more than likely its the knock sensor itself. New sensor time.

[Guest]

 boostin said:

But a knock sensor code doesn't mean it has sensed knock. It means the sensor resistance is out of spec. You'll need to check the resistance of the wire back to the ECU which should be 0.5 Ohms or less. If thats ok then more than likely its the knock sensor itself. New sensor time.

+1

[Guest]

 boostin said:

But a knock sensor code doesn't mean it has sensed knock. It means the sensor resistance is out of spec. You'll need to check the resistance of the wire back to the ECU which should be 0.5 Ohms or less. If thats ok then more than likely its the knock sensor itself. New sensor time.

its not too hard to change... did this nice and slow... good success