Anyone had this Issue

[Zuzbar]

Hi All,
Got a weird one here over the ditch, I have a 2004 Vitz/Echo/Yaris with the 2SZ-FE engine, Ran great for years for commuting to work but now has developed an annoying issue, When driving along the car will give a sudden *****, The High temp light comes on and the engine check light comes on when it does it and it only happens for a split second then goes out and the car runs fine until it does it again, It will sit and idle fine for ages with no issues, I changed the plugs, plug holders and coils, Changed the crank angle sensor, Cam sensor, Water temp sensor, VVT sensor, Have taken every plug i can see off and cleaned them with contact cleaner and yet the fault is still there, At present i have disconnected the battery to try and clear the ECU, Kind of running out of ideas here, Anyone else got any cunning plans out there???
Thanks

[campbeam]

Appears that you have thrown the "Parts Cannon" at this problem. This is an expensive approach. Better approach is to use diagnostics to actually determine the causes then start the eliminations to finally resolve the issue. Appears to be an intermittent issue caused by a bad electrical connection to the sensor instead of the actual sensor.

Have you used an OBDII scanner to determine if there are any error codes, especially pending codes? It may be necessary to do a scan when those warning lights are displaying.

[Zuzbar]

43 minutes ago, campbeam said:

Appears that you have thrown the "Parts Cannon" at this problem. This is an expensive approach. Better approach is to use diagnostics to actually determine the causes then start the eliminations to finally resolve the issue. Appears to be an intermittent issue caused by a bad electrical connection to the sensor instead of the actual sensor.

Have you used an OBDII scanner to determine if there are any error codes, especially pending codes? It may be necessary to do a scan when those warning lights are displaying.

The warning lights only come on for a split second, The car gives a "cough" then runs fine again for a little while then does it again, I have tried the OBD2 scanner trick but since it is only a split second it doesnt come up with anything hence me changing out sensors etc to try that route, Its got to be an electrical fault like you mention but its one of those head scratchers.

 

Edited February 6 by Zuzbar

[Zuzbar]

took it for a spin this evening, A couple of times it gave a jolt and when it does the engine check light comes on and the high temp light come on and then both go out after a second or two and the car runs normal again, Tried running it with the temp sensor disconnected, still does it, My cheap rubbish ozito scanner from bunnings will not talk to the ECU (Not the only car, Only talks to my Holden), Yeah got me stumped, A bit apprehensive to drive it too far. 

[Tony Prodigy]

I would take a look at the ECU itself. Pull the plugs, inspect them for any corrosion and if possible remove the ECU completely and open it up and see if anything is lurking inside. You could have some corrosion on the main PCB. Not knowing the history of your vehicle, I would guess if you live anywhere near the coastal regions, that moist, salty air can wreak havoc on electricals.

You've practically replaced everything that "could" be wrong, but my money is on the ECU. 

If you find a cheap "spare" ECU at a local wrecker, buy it and keep it as a spare, cos you never know when you'll need one. If you end up using it, it will need to be coded by someone with an appropriate scan/diagnostic tool or laptop with specific software. No big deal. There are plenty around who can provide this service.