Bypass knock sensor (1 Viewer)

[Chang739]

Hi guys, tried the search but could only find "replace KS or plug". 1995 1FZ-FE.

I'm getting code 52, tried to unplug the front sensor and it crumbled in my fingers. I have a new plug on express post however I need the 80 driving in a few days time to pick up a boat 5 hours away. How do I bypass the KS signal as a temporary fix before I can repair properly? I don't want to drive 10 hours with retarded timing. Does the wire need a constant 12V signal or a short to chassis to keep the EFI happy?

Cheers in advance.

Chang

 

[MickeyB]

Where you located at?

 

[UsedLuxury]

The proper term is mentally delayed

 

[Malleus]

Hi guys, tried the search but could only find "replace KS or plug". 1995 1FZ-FE.

I'm getting code 52, tried to unplug the front sensor and it crumbled in my fingers. I have a new plug on express post however I need the 80 driving in a few days time to pick up a boat 5 hours away. How do I bypass the KS signal as a temporary fix before I can repair properly? I don't want to drive 10 hours with retarded timing. Does the wire need a constant 12V signal or a short to chassis to keep the EFI happy?

Cheers in advance.

Chang

AFAIK, all sensors are "ground to complete the circuit" but that won't help you with the knock sensor. It actually has to "see" a knock to do its job. Having said that, again this is my understanding of the circuit, the sensor has to vibrate in order to send a signal to the ECM, and it has to vibrate at the correct frequency (6.1 kH @ 160 microsec). I don't think there's a way to "fake" the ECM, but, having said that, my son's 80 had two bad knock sensors for years, and it caused no problem at all (we had no idea they were faulty until we replaced the headgasket and the connectors crumbled in our hands).

If you're replacing the connector housing, you'll have to reinstall the terminals and new seals, because the Toyota housings don't come with either. Ballenger in the US has a "kit" that supplies the housing, terminals (with spares) and seals, for the knock sensor, for a better price that Toyota sells the housings alone.

I've attached the list of diagnostic trouble codes and the knock sensors section, for your use, however, according to my 1995 FSM, there is no code 52. I've seen this posted elsewhere, so maybe I'm wrong about this, but I can't find a code 52 in my FSM anywhere.

I did find (post #24) that someone years back claimed to have bypassed the ECM, but his post is thin on useful details. The knock sensor section I attached will help you identify the ECM terminals that need to be shorted, if you want to try that "fix".

 

[Malleus]

Hi guys, tried the search but could only find "replace KS or plug". 1995 1FZ-FE.

I'm getting code 52, tried to unplug the front sensor and it crumbled in my fingers. I have a new plug on express post however I need the 80 driving in a few days time to pick up a boat 5 hours away. How do I bypass the KS signal as a temporary fix before I can repair properly? I don't want to drive 10 hours with retarded timing. Does the wire need a constant 12V signal or a short to chassis to keep the EFI happy?

Cheers in advance.

Chang

After giving this further consideration in the reading room this morning, I think you may be able to cheat the ECM by tying the knock sensors together, since they "report" to different ports (I assume this is what @jblaze was referring to in his post #24 above):

This assumes that you actually have one good knock sensor. As I said above, the sensor has to vibrate in order to send a signal, and the signal it sends has to be the right one.

You could install a jumper at the ECM, between terminals 6 and 14 (under the glovebox),

or at the engine side, between the two connector housings. The ECM jumper would be shorter, and, at least on my engine, easier to get to, but it wouldn't matter where the jumper was physically, as long as it was in the circuit.

 

[Chang739]

After giving this further consideration in the reading room this morning, I think you may be able to cheat the ECM by tying the knock sensors together, since they "report" to different ports (I assume this is what @jblaze was referring to in his post #24 above):
View attachment 3251455
This assumes that you actually have one good knock sensor. As I said above, the sensor has to vibrate in order to send a signal, and the signal it sends has to be the right one.

You could install a jumper at the ECM, between terminals 6 and 14 (under the glovebox),
View attachment 3251461
or at the engine side, between the two connector housings. The ECM jumper would be shorter, and, at least on my engine, easier to get to, but it wouldn't matter where the jumper was physically, as long as it was in the circuit.

Thanks Malleus; it's an oddball because the nameplate says 1995 80 series, however it lacks OBD and instead has the old style diagnostics plug that requires the jumper wire to read the codes. I believe this is an Australia production quirk. With the old style, code 52 is a missing signal with KS #1. See attached Haynes manual.

Bridging KS #2 with #1 sounds like it would work, however I have since soldered a piece of wire to the old plug and then to the engine harness wire as a temporary fix. When the new plug arrives (From EFI Hardware: 1 Pin Toyota Knock Sensor Connector - https://www.efihardware.com/products/2817/1-Pin-Toyota-Knock-Sensor-Connector) ill have it properly crimped.

It makes sense in hindsight but I didn't anticipate the KS requiring a frequency signal: I assumed it was an "on/off" trigger that either shorted or provided a resistance. Thanks for the info.

Cheers,

Chang

 

[Chang739]

The page from the Haynes Manual:

 

[SmokingRocks]

tie them together it’s the same as obd2 get your fsm (93-94) from the link in my signature.

It has the electrical wiring diagrams all bookmarked.

Tie them together and see if that works

 

[tlc1995]

The proper term is mentally delayed

Todd

 

[Chang739]

I ended up gluing the old plug back together then soldering a bit of wire to it, then soldering to what was left on the harness end and plugging it back in. CEL gone, its getting a signal from the #1 knock sensor now. Temp fix will have to do until the new plug arrives and I can get someone with a proper crimp to install it. Cheers for the help in any case guys

 

[Malleus]

FWIW, the Toyota FSM for your year is available for download for free. Highly recommended.

 

[SmokingRocks]

yea toss the haynes manual, they don't hold a candle to the Toyota FSM you'll understand when you get into it. Again link to the resources section is in my signature.