1uzfe knock sensor wiring shielding ground point

[chowdah]

I’ve been working on adding new wiring EMI shielding for my knock sensors wiring on my 95 sc400, i have a drain wire set up to a chassis ground point but wondering if it needs to ground to the engine block, can/should it ground to both? or only one specifically? i was never sure about the factory (it’s supposed to be shielded from factory, right?) -shielding’s ground point and can’t really figure it out. Testing the existing one i’ve discovered it has no continuity so it’s not grounded as far as i can tell. I’m not super experienced in electrical work, trying to do good research and just want to make sure its done right so i dont have to worry about it again.

 

[P Bateman]

In the factory wiring, Shield connects to ground on the engine.
In most aftermarket ECUs though, Shield Ground comes from the ECU.
As long as all your ground points have good contact, it shouldnt matter... but the more ground points you have - the more possibility there is for problems to arise.

Good article on it here.

https://www.haltech.com/news-events/ecu-grounding-the-dos-and-donts/

 

[chowdah]

Sorry for the late reply, but thank you for the information. I have a refurbished ECU from flagship one. Do you think it needs to be grounded to this ECU? Code comes back whether or not the ground point is on engine block, battery, or both.

Link to the specific ECU i have -

89661-2441184 | 1995 Lexus SC400 4.0L ECM Engine Computer PCM ECU Programmed Plug&Play

Engine Computer fitting all 1995 Lexus SC400 4.0L models with matching computer service number 89661-2441184. This unit is also compatible with the following service numbers 89661-24411-84; 9617509-784.

www.fs1inc.com

 

[P Bateman]

What code are you getting?

 

[chowdah]

52

 

[P Bateman]

52 = no knock signal to the ECM for 3 engine revolutions when its between 1600-5200rpm
Its is either going to be an open or short in the sensor circuit, the sensor itself or the ECM.
Shielding only in there to dissipate interference.

 

[chowdah]

I was working on this with my friend originally on this job and we redid the wiring to the pigtail. He used heat shrink solder for the wire splice and i’m wondering if that could have caused an issue, people say they’re bad in high vibration environment (ofc i only hear about this after he uses these things) I am of course going to test the sensor itself as well.

Another lesson learned i suppose.

 

[P Bateman]

The test procedure is simple - measure resistance between the KNK input on the ECU to ground.
Spec is 1 mega-ohm (MΩ) or more.

I'm not a fan of soldering mission critical wiring - even less for heat shrink solder.
Barrel crimps are the go!