cas codes 46 47

[Jxw]

Recently helped diagnose a vt that had intermittent problems for over a year, would have the common stalling/stopping problem occasionally then refuse to start again, was really waiting for something to fail to be able to point the finger at and i forgot about it as the owner didn't mention it again, it just kept going with the occasional annoyance till recently it got more frequent.

Problem fault codes that came up were 31 46 47 (at least 31 explains the occasional refusing to start issue)

Advised the owner to replace the cas and dfi module as they needed the car for an interstate trip and we thought it best to have all the known components replaced instead of changing 1 thing and finding out 600km's later when it completely stopped that it was another part, his mechanic agreed and did so.

I got my hands on the old components to test. Visually inspecting the cas i noticed something odd, there's a heap of fine ferrous particles hanging onto the magnet, best conclusion is that all this has built up over time from road debris, shit in the air and/or from washing the engine bay in car washes that recycle their water, i'd guess it's not iron or steel as it's a fine black mess and no sign of rust amongst it........




From the amount of buildup i'm pretty sure it'd be upsetting the sensor, changing the air gap and these particles would be moving around from vibration and the wind from the blades messing with the magnetic signal.
After all it's a hall effect sensor... magnet on 1 side with a coil of wire on the other and another piece of metal spinning with openings cut into it blocking/allowing the magnets influence on the coil.... no rocket science here, it may be a basic construction for an electronic sensor but needs to be precise and accurate... 1 part of the sensor is opening and closing approximately 37.5 time per second, the other side of it at 225 times per second at 750 rpm idle, increase the rpm and well you can do the maths at how many times the signal turns on/off

If you get some of these symptoms one of the first things to try would be to get an air gun & air compressor (make sure you wear the correct ppe... goggles, bullet proof vest, crouch cup to protect yourself from flying debris)..... and give it a good blast around the cas and the shield, may be a pain but try and hit it from every angle possible with some high pressure air to dislodge any magnetic material stuck to it.

No check engine light on either car when the engine was running on either the original vt or vr.

Testing components so far:

coil packs work perfect on another module.

Tested the dfi module in a vr: ran but lacked response when quickly hitting the throttle from idle in neutral, started running rich and missing under acceleration, idled fine once it was let go.
Slowly opening the throttle it increased rpm ran fine and didn't miss a beat.....
Error codes 47 & 49 shown on the vr diag, reset codes.... let sit for 10 mins started, same errors but only when opening throttle quickly.

Inspecting the dfi module, some pins are slightly corroded and seem tarnished/dull, had to look really close under a good light source to see, at first quick glance it looked fine, cleaned with emery paper, no change, covering the connections with crc/inox when installing a new module should protect the pins from corrosion.
Got the module apart and cleaned the clear crap off the circuit, failure was due to dry solder joints on the small ic's loosing contact with the engine vibration, if you have a smd rework station and are confident to reflow the solder you should be able to fix these, not a beginners task though.