G28, G40 and G4 sensors

[BrianSmith_S2]

So the G4 plot is worrying, but does the fact im only seeing 4V at the G28 indicate a fault elsewhere?

By the way i scoped one of the injectors and nothing, not a sausage, and both pins made a beep on the continuity test

The scope i borrowed from work only has 1 channel i might have to borrow the picosope data logger/scope tomorrow... 16 channels through to the laptop, i will be able to scan every sensor simutaniously on the S2 then:mischeif:

[S2central.net]

Dont worry about voltage for now - shape is more important... your probes and/or scope setting could be skewing things too in that regard.

No injectors will pulse if ECU doesnt know where crankshaft is - G4 missing. It likely enables the fuel pump cos it sees lots of crank pulses from G28.

[BrianSmith_S2]

Your traces have a range of 500mV - so you are either -

1 - just picking up noise and not triggering on G4 correctly
2 - crank reference pin is broken off
3 - G4 sensor is dead... you know it is same part as G29 sensor - so swap them over and see if badness moves to G28 signal with same sensor and hope that you can see G4 signal with the other sensor

Yep, i will try that next.... and will also tap a screwdriver across removed sensor to calibrate scope

By the way Paul, im probing off pin 3 (common) and pin 2 (signal) on each plot, hope thats correct.

[S2central.net]

Err no... G4 and G28 signals are between pins 1 & 2 - the wires that are not black if you can see them better than pin numbers. Black wire, pin 3 is just a screen.

[BrianSmith_S2]

Err no... G4 and G28 signals are between pins 1 & 2 - the wires that are not black if you can see them better than pin numbers. Black wire, pin 3 is just a screen.

ok, i will re do the test plots tomorrow over the correct pins and see how they come out.

Thanks for your patience, this probing lark is fun

shame vag com history cant be in the form of a picoscope data log that can be down loaded through a usb slot in the relay box.

[S2central.net]

Another thing to check is that you are seeing 12V on the black/grey wire on auxiliary relay number 10 - when key is on at least.

[BrianSmith_S2]

Another thing to check is that you are seeing 12V on the black/grey wire on auxiliary relay number 10 - when key is on at least.

Is that the fuel pump relay? It does seem to function ( i removed its cover) but will check what youve said after work.
I guess the fuse box is easy to lift out and get access to this black/grey wire beneath the relays.

[S2central.net]

NOT fuel pump related... Do NOT lift out main fusebos - its a beeatch with lots of sealant and pain involved.

I am talking about relay #10 (carrier 204 label) in the wiring panel above drivers pedals - do you need a pic ?

[BrianSmith_S2]

NOT fuel pump related... Do NOT lift out main fusebos - its a beeatch with lots of sealant and pain involved.

I am talking about relay #10 (carrier 204 label) in the wiring panel above drivers pedals - do you need a pic ?

I remember seeing that wiring panel after my clutch master cylinder failed, i will check that out after work

What does this relay power up? is it injector/ignition related?

Fingers crossed it will be this and not the pin activating the G4 thats at fault. A correct probe with oscilloscope over pins 1 & 2 of the G4 and G28 will be done later as well

[S2central.net]

Its ECU related - if ECU doesn't get 12V on that pin then it will not power up fully - regardless of health of signals from G4 etc

[BrianSmith_S2]

Err no... G4 and G28 signals are between pins 1 & 2 - the wires that are not black if you can see them better than pin numbers. Black wire, pin 3 is just a screen.

Re probed the G4 and G28 over pins 1 & 2

The plots look a better shape, and slightly relieved because it looks like my flywheel pin is still there with a pulse around the 300ms mark as expected but the voltages look low

[BrianSmith_S2]

NOT fuel pump related... Do NOT lift out main fusebos - its a beeatch with lots of sealant and pain involved.

I am talking about relay #10 (carrier 204 label) in the wiring panel above drivers pedals - do you need a pic ?

I removed panel above pedals and didnt find what i was expecting. Instead of a board bristling with relays and fuses all i find is a board as shown in photo.... not sure what im looking for

[BrianSmith_S2]

NOT fuel pump related... Do NOT lift out main fusebos - its a beeatch with lots of sealant and pain involved.

I am talking about relay #10 (carrier 204 label) in the wiring panel above drivers pedals - do you need a pic ?

I would love a pic Paul......

[BrianSmith_S2]

Just probed the G40 and G40 using a 2 channel scope and got the following plots.

The G4 is spiking 1V twice between each of the 3V 40ms pulse from the G40.

The first G4 spike is approx 200ms after the end of the G40 pulse, the second G4 spike is 120ms before the start of the next G40 pulse.

They seem out of sync with the G40, is this normal?

Cheers,

Brian

[S2central.net]

Brian. That scope plot proves your timing is way off. The G40 pulse should align with alternate G4 pulses from the crank. This doesn't look like a bad sensor - it looks like a slipped belt or sheared key on the camshaft or crankshaft.

Look at the plot I posted on mine earlier in this thread. I can dig out others and/or draw something if you would fin it helpful.