Electrical issue

[chaingun427]

Technically speaking this isn't for a NBS tahoe, it's on my swapped 98.

little background, it's an 02 5.3l, and i've swapped in the gauges and BCM from the truck as well. Recently when the engine is started it will kill the class 2 data, so that I lose all of my PCM controlled gauges. Engine runs fine. If i unplug the alternator the gauges are fine, but if it stays running it kills the PRNDL and fuel level gauges, and the security light comes on. Any ideas would be helpful

 

[SLCHOE]

Sounds like something is corrupting the data line. What is the voltage on the data line and what communications code(s) are you getting? Also do you have a scan tool?

 

[chaingun427]

No codes, which I thought was odd. I never thought to check voltage, it should be near 0 right?

Found some issues with my cluster and bcm class 2 lines, but correcting them didn't change the result. I'll check that voltage tomorrow, if I've got voltage I'll start tracing it down. I wonder if one of the obs modules like the keyless entry could be to blame.I'm not sure what all runs on the class 2 bus in the obs

Sent from my SAMSUNG-SM-N920A using Tapatalk

 

[SLCHOE]

No codes, which I thought was odd. I never thought to check voltage, it should be near 0 right?

Found some issues with my cluster and bcm class 2 lines, but correcting them didn't change the result. I'll check that voltage tomorrow, if I've got voltage I'll start tracing it down. I wonder if one of the obs modules like the keyless entry could be to blame.I'm not sure what all runs on the class 2 bus in the obs

Sent from my SAMSUNG-SM-N920A using Tapatalk

No not zero. Key on engine off IIRC it's like 2.5 Volts and using a scope it should be sqaure wave forms oscillating between 2.5 and 0 volts. Whatever voltage it is with a multimeter isn't as important as the square-wave pattern though. This is a digital data line and there should be a set voltage for (on) and low (zero for off). If you scope it out and it's 12v flat signal, you have a faulty module or a source wire feeding into the data line that should not be tied in.