How Do You Test A Cas Sensor ?

[jonand 0]

Help !!!

 

Mi16 wont start and it appears that there is no signal coming back from the CAS sensor in order to tell the ECU that the engine is turning. I have 512 ohms resistance across two of the pins, but cannot generate any signal when cranking - I have simply put a voltmeter across the (connected) pins then cranked the engine. Am I doing the wrong test ?

 

Thanks in advance

Jon

[jackherer 543]

512ohms is about right for a static test, but to dynamically test it with the engine turning over you really need an oscilloscope to check for a square wave.

 

If you're not getting fuel or spark and the ecu has power then its likely to be the cas, but if you are getting either fuel OR spark then it isn't the cas.

[jonand 0]

512ohms is about right for a static test, but to dynamically test it with the engine turning over you really need an oscilloscope to check for a square wave.

 

If you're not getting fuel or spark and the ecu has power then its likely to be the cas, but if you are getting either fuel OR spark then it isn't the cas.

 

OK thanks for that.

I'm not getting spark or fuel, and there is power to the ecu. I thought there may be a way of crude checking, but my knowledge drops short of understanding how the cas works.

 

Cheers

Jon

[jackherer 543]

I thought there may be a way of crude checking

 

you can kinda move the sensor over somethng metallic while measuring the resistance to see if it changes but its far from conclusive so a waste of time really.

 

the easiest way to test is with a new cas, its worth having a spare one to hand anyway for these sort of situations.

[jonand 0]

you can kinda move the sensor over somethng metallic while measuring the resistance to see if it changes but its far from conclusive so a waste of time really.

 

the easiest way to test is with a new cas, its worth having a spare one to hand anyway for these sort of situations.

 

Yes your probably right - looks like I'd better get spares of all the sensors etc. The bits you want are never available when you need them most

 

Cheers

Jon

[jackherer 543]

yeah definitely, for an Mi16 you ideally want a known good cas, an ignition amp, an afm, an ecu water temp sensor and a dizzy cap/rotor arm to hand IMO.

[jonand 0]

yeah definitely, for an Mi16 you ideally want a known good cas, an ignition amp, an afm, an ecu water temp sensor and a dizzy cap/rotor arm to hand IMO.

 

 

And probably a spare engine for when the dreaded oil surge wrecks the current one !!!

 

Thanks for your help

 

Jon

[kate205gti 4]

lol yeh unfortunately true! best bet is to find someone with a working mi16 who can pop over and swap bits over to diagnose! then buy the bit when u found out what it is

 

or just buy spares of everything if u can, but i have bought "duff" sensors before brand new so always handy to have a second car to try them on

[jonand 0]

lol yeh unfortunately true! best bet is to find someone with a working mi16 who can pop over and swap bits over to diagnose! then buy the bit when u found out what it is

 

or just buy spares of everything if u can, but i have bought "duff" sensors before brand new so always handy to have a second car to try them on

 

Yes that would be useful - Anyone in the Milton Keynes Area with an alloy block Mi running Motronic 4.1, that would be prepared to try my components PLEASE.

 

I have tried another CAS sensor today - but no different. The inj relay is operating OK, but the pump relay is not earthing through the ecu - I am now wondering about the ecu.

 

Help

Jon