Kbus voltage

[Richym]

What voltage sould be in kbus system?

Mines is only showing 3.5v and i guess thats why i am having problems.

Is there anyway of isolating different areas that use kbus to try and narrow down the problem. I have tried the usual fbh, under seat header and stereo.

Doors unlock but wont lock and passenders door is dead altogether. Everything worked fine until i had my little water leak

Thx richy

[andrewinpopayan]

Water leak? pray tell us more about your woes with water............

Has anyone put an oscilloscope onto the kbus?, have you FrenchMike ?

[Avora]

KBUS voltage should be up around 12V. Test it in lots of locations to get an idea where the problem is. More than likely corrosion, or possibly the wire has rubbed through.

[HarryM1BYT]

KBUS voltage should be up around 12V. Test it in lots of locations to get an idea where the problem is. More than likely corrosion, or possibly the wire has rubbed through.

KBUS carries data, it will vary between data high and data low as it transmits data. Yes I have had a scope on it, but I don't recall the high and low values - I would expect high to be 5v, as that is more usual. A meter will not show it, though it may show varying values whilst transmission is taking place.

[Richym]

Eventually got to the bottom of it. Cut the kbus wire that runs from front to rear along drivers door and all works well again. I did check the plugs in the rear of car and found no corrosion or problems. Sooo Happy tonight i think i might have a beer or two

Thx for everyones help

Richy:}:D:}:}

[FrenchMike]

KBUS carries data, it will vary between data high and data low as it transmits data. Yes I have had a scope on it, but I don't recall the high and low values - I would expect high to be 5v, as that is more usual. A meter will not show it, though it may show varying values whilst transmission is taking place.

Kbus logical levels : 0 and 12 volts ,Harry :}

[Avora]

KBUS carries data, it will vary between data high and data low as it transmits data. Yes I have had a scope on it, but I don't recall the high and low values - I would expect high to be 5v, as that is more usual. A meter will not show it, though it may show varying values whilst transmission is taking place.

The bus is normally high. So should show ~12v and is readable with a multimeter.

[Phil-T4]

Kbus logical levels : 0 and 12 volts ,Harry :}

Very close, its 0 to Vbatt volts ;) :D :getmecoat:

[andrewinpopayan]

So it's sending data, probably the kbus line has a high impedance source, any leakage would drag the "1" voltage low and produce all sorts of spurious faults, even the meter used to read it's voltage may represent a significant sink load.

[HarryM1BYT]

So it's sending data, probably the kbus line has a high impedance source, any leakage would drag the "1" voltage low and produce all sorts of spurious faults, even the meter used to read it's voltage may represent a significant sink load.

12v it is then...

It will be what is called 'open collector', so any data source can transmit. When a source wants to send data, it will first listen, then transmit if the line is free. It will repeat at intervals until it gets an acknowledgement back.