An intermittent CEL light was flickering when I started the car up after I fitted a replacement engine (V8 sti short block and used my P1 heads. The car was off the road for 2 years waiting on the new engine and I originally thought it was the 2 year old fuel I had in the tank that was causing the knock sensor to throw up up a fault so drained the tank and filled it with some fresh momentum and for good measure put in some octane booster.

I reset the ECU and ran the car on idle a few times with no CEL light reappearing. Today I took the car for a short run round the neighbourhood and the light came back on.

I have now removed the sensor and gave it a visual check to see if there was any signs of damage to the casing which there was none and also checked its resistance which measured 4.86Mohm. From research, anything over 4.6Mohm is good.

Fitted the sensor back in and reset the ECU again, checked for codes and there were none, fired it up and the CEL light came on immediately. Checked the codes again and it showed code 22 for the knock sensor.

I'm now wondering if it is the sensor is faulty or if it is detecting knock somewhere. Any thoughts what the issue could be? The MAF sensor is brand new and has just been fitted during the engine swap.

Supposed to be getting the car mapped next week so need to find a solution quick.

 

My knock sensor went faulty but I can't remember if it flashed the light or it stayed on. I did see some cracking on my old sensor though. They aren't expensive so maybe it would be worthwhile replacing it.

 

I have problem with replacing it but as it looks to have no sign of damage and is giving a resistance of 4.86Mohm, is there any point?

Is there any other checks that can be done to test the sensor?

 

Honestly I don't know, does the CEL flash on boost or just at random intervals?

 

It stays on solid now. Until it's mapped, it's not seeing boost.

 

I'd say the sensor is at fault then mate. Just make sure it's plugged in properly and torqued properly I suppose. The cracks can be very small and can let moisture in to the sensor. Is it an old one?

 

It's torqued up to 24Nm and showed no signs of cracks but it is old. It was the original off my P1 and AFAIK has never been changed so is 15 years old now.

Maybe just getting a new sensor is the only option at this point.

 

Maybe disturbing it has caused the issue. It's been through thousands of heat cycles and would be brittle by now I'm sure. When I replaced mine and reset the ecu I had no further problems at all. I think my car went better afterwards!

 

Cheers mate, I ordered a new one from ICP so hopefully will get it early next week and see how it goes after fitting it.

 

@ScoobP1, I know this is very old, but have you ever measured the resistance of the new knock sensor, for comparison? I'm having a similar issue and a similar value on the now ancient KS, 4.7 MOhm.
Also, did the new KS solve your issue? Thanks.