Knock Sensor Fault

[Trevor]

The ECU warning light came on on the way to work this morning and checking the fault codes the main one seems to be for the knock sensor(s). This seems to be born out by the engine behaviour - fine up until 4500 rpm then the engine starts to sound very rough, which I presume is due to the ECU falling-back to a default ignition timing. I have mow reset the ECU so will check again this evening.

Meanwhile the questions:-

Are there one or two knock sensors fitted to the Turbo?
If two, how do you tell which one is faulty?
How much is a new knock sensor from Toyota?
Cheers,

[Lofty]

Yes there are 2. They work just like microphones I believe so they could be tested with an oscilliscope I guess. It could just be a wiring problem as I am sure I have read a SOGI article about rewiring using RG58 computer cable.

[Nick@TC]

Yep, first thing to look for is a wiring problem.

I brought one from Toyota about 18 months ago and it was £112 iirc.

[Trevor]

Thanks for the replies.

I'll see how things go on the way home tonight. If it's OK, or at least intermittant, I guess it will be a wiring fault.

PS. Cheers Lofty, for the steering column procedure you posted on Smartpoops a few months ago. The NA now has a working horn and cruise control.

[Lofty]

I'd forgotten about that cruise control fix. Glad it did you a good turn. If you decide to do the rewire and need some RG58 (you'll want stranded not solid core stuff) I still have half a reel knocking about somewhere I think. We don't use it anymore so I can chop a piece off for you. Best check out the article and see what it says.

[Trevor]

I'll see how things go on the way home tonight. If it's OK, or at least intermittant, I guess it will be a wiring fault.No knock sensor fault on the way home, or to work this morning, so probably a wiring fault coupled with heat soak as I had stopped for 5 mins on the way to work and the fault happened shortly afterwards.

However, checking the fault codes last night 51 has come up again. I have checked this online, but basically I'm no wiser. Could someone please explain further. Does A/C mean air-conditioning, or something else?

Here is the description:-

51Switch Signal Diagnosis

No "IDL" signal, "NSW" signal or "A/C" signal to ECU, during diagnosis check.
Trouble Area

A/C switch circuit
A/C switch
A/C amplifier
Throttle position sensor circuit
Throttle position sensor
ECU
Also I get a misfire between 1200 and 2000 rpm. This might be a CPS fault, but could it also be related to this fault code?

Cheers,

[Lofty]

If you have been poking about in your engine bay recently, presumably checking the knock sensors, then the first thing I would check is that you haven't disturbed and electrical plugs or vacuum hoses. You could also check for cracked vacuum hoses too. Might be worth checking the ECU connections and nearby earths. Failing that I think I would check out the Throttle Position Sensor (TPS) as per the TRSM and adjust accordingly.