[SaVAGeSoot]

sees low v signal

Are we talking about the same fault?
Because I'm reading high signal in what you posted above!

1 Fault Found:
01598 - Drive Battery Voltage
001 - Upper Limit Exceeded

 

[Oldo]

Hi...took a few days out in the Alps. Story so far, nothings changed. Attached find a really odd vcds scan of address 34 done a couple of days ago. How a 12v battery can produce 18+ volts (ignition on engine not running) in a 2x12v parallel circuit is beyond me, terminal 15 is showing 11+v on a battery SoC @ 12.77v. It's the only circuit/address to show 01598 fault. Thinking probs with j403 but it's new along with the compressor but symptoms existed prior to fitting them, any thoughts?
Cheers

 

[SaVAGeSoot]

I'd bust out a meter and wiring diagram and back probe that terminal 30 line to see if there's 18v there somehow

 

[Oldo]

Burnt out two 9v batteries on my dvom already, all I can think of is there is an anomally in the voltage control module since changing batteries. The T1 does not let you register a new battery, so I think the module is seeing the old battery values (the battery was 15 years old, but I changed it on a whim not because it was dead); 12 volts are a nominal value but amps matter to the EMU and module boards as they cause heat and disruption to circuits. The original g8 batteries are no longer available except from dealerships 300euros+, but those are questionable as varta stopped producing them in 2020, not sure dealers are gonna keep them 100% viable for 2-3 years. Anyway, still cannot see how i=vr can produce 18+v from 12v without adding additional circuitry that is no apparent in the wiring schematics.
More trials tomorrow, enjoy your weekend.
Cheers

 

[Oldo]

Hi, finally got some air into the resevoir by runnning the engine and holding (bridging) the relay so it's less like an amusement park ride today. One question; do you know what module could be seeing/reporting the 18v? Reference volts 12.5v are at j197 at pins 3, 4 and 5 and fuses sc27 and sc48 and the module is working because it's giving feedback in the scan. The only other modules j197 communicates with directly are j533 and j519 on can-l and can-h, but I'd be surprised if they survived 18+v . I'll look at the board of j197 tomorrow. If 18v has actually gone through it, some of the processors will be toast and showing scorch or burn marks. Since getting some air it now takes longer for the MIL to report.
Cheers

 

[SaVAGeSoot]

What's happening on pins 36 & 31 on the J197? Isn't that the link to your relay?

 

[Oldo]

I'm assuming they're ok because it allowed air into the resevoir and prior to bridging j403 the relay did not go positive so j197 did not see the volts from it; but I'll check tomorrow before I pull the board

 

[Oldo]

Found an 18+v spike (goes back to 13-14+v in the blink of an eye) on startup on the main left hand side harness, it's really quick (ms event) but enough to trigger the dtc. Tomorrow try and find its origin, but pretty sure it's a relay under drivers seat, only 2 to choose from and neither in production!