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Ask Dave Nova Your Own Question
Dave Nova
Dave Nova, Cadillac Technician
Category: Cadillac
Satisfied Customers: 1522
Experience:  ASE Master Certification. GM World Class Certification
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U1300, 2003 cts 3.2, I am fixing it myself. I tried the ecm

Customer Question

JA: What is the model/year of your Cadillac?
Customer: 2003 cts 3.2
JA: Are you fixing your CTS yourself? What have you tried so far?
Customer: I am fixing it myself. I tried the ecm originally because the ecm was resetting during cranking. Now I have this problem where the theft system will not unlock and the U1300 on the ECM. Voltage levels on the buss are only about 6 1/2 volts average with fluctuation during the transmit packets.
JA: Is this your first time dealing with this issue?
Customer: yes
JA: Anything else you want the mechanic to know before I connect you?
Customer: No
Submitted: 1 month ago.
Category: Cadillac
Expert:  eric remington replied 1 month ago.

You need a scanner that is sophisticated to communicate with antitheft system bcm

Customer: replied 1 month ago.
I have an autel maxsys elite. My question was regarding voltage levels on the class two data bus. Will a 6.5 volt level on the bus throw a 1300 error.
Customer: replied 1 month ago.
the U1300 error is the the ecm. Random modules have a u1000 error. They are not positioned together. Lots of modules fail with U1000 while the next in the chain has no fault.
Expert:  eric remington replied 1 month ago.

I suppose it would depend if it was meant to be a 12 volt circuit at the time. So you have scanned all modules and all you get isa u 1300 code? is that the only code you need info for? the buses are shared circuits so its hard to say

Expert:  eric remington replied 1 month ago.

too big a voltage for a five volt circuit too small for a 12 volt. I would stick with trying to diagnose the codes and after that you may not get 6.5 voltages....

Expert:  eric remington replied 1 month ago.

ss do an all module scan and list all codes and lets go from there

Expert:  eric remington replied 1 month ago.

your question had to do with voltage levels?

Expert:  eric remington replied 1 month ago.

alldata doesn't list an u 1300...doesn't mean it doesn't exist it just means I don't have info so I will let another expert help