CAS diagnosing steps?

honduraneclipse · 08-22-2006, 07:45 PM

How are you guys diagnosing the CAS problems? Is there a voltage available or drop test you can do? How about a ground test or resistance test? let me know , right now my 90 tsi awd with a 92 wiring harness is having a no start problem. I have 165 compression across the cylinders. I tested the fuel pump and get spark once in a while.
I know my mpi relay and ecu work also because i tested them out in another car. finally but not least I have available voltage at the injector clips but when I try to turn on the car it seems it is not been grounded.
I am leaning towards the CAS and the injector resistor, but I want to diagnose these problems without going through all trouble of taking these parts out and trying other known good ones.

I have diagnosed a couple of no starts but nothing like this. I just wish I had more money to buy the "special tools" to diagnose this problems more accurately.

steve · 08-22-2006, 08:17 PM

There are several types of CAS but they are either 90 style with a pigtail coming out of it or 91-94 style with a connector on the CAS. The CAS has four wires. Two are for the 12v (red, pin 3) and ground (black, pin 4).

The other two are the signal wires for the TDC and Crank Angle inputs to the ECU. They are pulled up to 5v by the ECU and the CAS pulls them low to signal. TDC will pulse twice per rev and the Crank Angle 4 times per rev. Turning the CAS by hand will allow you to see the signals with a voltmeter and test it's operation. It has to be plugged in or you have to make a test harness to provide the correct voltages.

It's still possible for the CAS to be bad when hot or at speed but this will identify the really dead ones.

Steve

Beanokid69 · 08-14-2007, 04:34 PM

ok so the TDC wire should be pulled up to 5v right? And that corresponds to pin22 on the ecu yes or no? my wire is dead all the way back to the ecu if it is and I dont know why....this is the second ecu in my car with that dead wire.

M Diver · 08-14-2007, 05:49 PM

I just thought I had a dead CAS too, and someone told me to turn the ingnition key to the on position with the CAS removed from the engine but still plugged in. Then to hand turn the CAS and you will here the plugs and injectors firing. I did this test and could here them fire... I don't know how good this test is for under heat or at speed, but at least you know it is responding...

Beanokid69 · 08-14-2007, 08:40 PM

ya i did that test too and I get nothing

punkrocker00406 · 10-14-2007, 04:43 PM

Hi, I'm getting the cas code on my 90 tsi. The light comes on and goes off randomly. The car runs perfect going down the road, but some times when starting it struggles to start and if it starts sounds and feels like its only running on 2-3 cyls. Then if I try to start it again it usually starts right up, runs and drives perfect. Does this sound like a defective cas.? Thanks.

mrmitsu · 07-31-2012, 05:05 PM

^
I WISH someone replied to this last post!

I'm experiencing the same symptoms.

Does anyone have any input on the topic?

Thanks!

shane90gsx · 07-31-2012, 05:35 PM

Quote:

Originally Posted by M Diver

I just thought I had a dead CAS too, and someone told me to turn the ingnition key to the on position with the CAS removed from the engine but still plugged in. Then to hand turn the CAS and you will here the plugs and injectors firing. I did this test and could here them fire... I don't know how good this test is for under heat or at speed, but at least you know it is responding...

If you do this, and you don't hear the injectors or no detectable voltage when turned then u need a new CAS. Another way to test is your engine should crank, and your RPM gauge will not move at all. My car would randomly fire and the tach would stay planted.

1gAWD92 · 12-11-2012, 01:01 PM

Quote:

Originally Posted by shane90gsx

If you do this, and you don't hear the injectors or no detectable voltage when turned then u need a new CAS. Another way to test is your engine should crank, and your RPM gauge will not move at all. My car would randomly fire and the tach would stay planted.

it sounds like this is the answer to the OP, im having the same problem in my 92 rs. just got it towed from the shopping center like 2 hours ago

got it home and checked the fuel pump, that was working. checked for spark, i had spark. check to see if i was getting voltage to the injectors, and i was getting voltage there... but not much like 1 volt constant (injector 1).. a fellow tuner told me today that if you have lower voltage at injectors 1&4 you my have a bad CAS and i checked injector 1 so lets hope that its just the CAS