U1040 grand am - 2001 Pontiac Grand Am SE

Need more info and U1040 is a bcm code, loss of communication .is this vehicle new to you? or can you give info of events that occurred prior to malfuction light illuminating . Vehicle engine size would help with suggestions on where to start your troubleshooting. but quickly Did you check all fuses? You Have multiple fuse Box locations. Not just underhood. That would be a good place to start your diagnosis.

I’m happy to assist further over the phone at https://www.6ya.com/expert/james_9ddabbbc483e2add

p0504 brake switch A/B
break light switch, fuse or light bulb
p1629 theft deterrent system cranking single

U, B, C and P codes above P0800 are considered enhanced manufacturer specific codes. So without knowing the year, make, model and engine, nobody can answer your question.

check the video although it od 2002 model.

2002 2005 Buick Rendezvous body control module BCM Genuine OEM...

Loss of Class 2 Communications with ABS

DTC U1040 indicates that the ABS module is not capable
of sending its state of health message. ( and this makes the ABS Light not flash ) check connections on the Module ...all fuses ...

Possable causes :
Open ABS fuse
Open battery circuit
Open ground circuit
Open serial data circuit
Short to ground in power circuit
ECU malfunction

I found a code chart at another web site.U1040 indicates no serial data communication with ABS module.I checked for wake up signal,it was there.I checked ground connection,it was good.I checked for B+ at module with DVOM and had battery voltage at both pins.I then load tested both B+ terminals and found the circuit was faulty.I went to the 30 amp ABS fuse and did a voltage drop test .I found the female connectors that the fuse plugged in to did not make good connection with the fuse.I bent the fuse pins outward and reinstalled.The ABS module came back on line.This bike has less than 2500 miles on it and this connection is already faulty.Is there a way to look up TSB'S for harley?.Bending the fuse pins is only a temperary fix.If there is no TSB for this problem I'm going to wire in a ATO fuse instead of the mini that Harley uses.The ABS motor draw on every start up appears to be excessive for that mini fuse connector.

what does u1040, c1298, and c1248 mean for my car?

first clear all the codes and drive to see what codes come back because some of the code could have been in history
for awhile then recheck and start with the current codes

Hi, if you are receiving a u1040 code ,the car needs to be put on a good scanner to see which module is not communicating this includes the pcm-ebcm-bcm-sir/sdm-ipc-radio and the pass key 111, you need to check the battery hots, ignition hots ,grounds and serial data lines to each module if the scanner cannot communicate with any of the modules, the serial data line will have a very low amount of voltage and will be moving between low voltages check all the fuses and relays battery connections and grounds, the ignition relay is a good one to check, also for the antitheft reprogram relearn there is a 30 minute relearn process ;;try to start the vehicle and release the key do not turn it off wait ten minutes until the security light goes out then turn the key off for 5 seconds and turn the key back on wait 10 more minutes for the light to go off again turn the key off for 5 seconds and then back on for 10 minutes more after the light goes off turn the key off for 5 seconds and now try to start the car, if it still doesn’t start then check for any connections under the hood for water damage or critter damage.

Take care

P0621 - indicates a failure in the alternator lamp curcuit.
P0304 - indicates a miss fire was detected in the #4 cylinder
U1040 - indicates a loss of communication with the ABS system
U1000 - Indicates a class 2 communication loss

None of those codes are relating to a transmission failure (P0700-P0702)

I would have a visual look at the transmission and verify that all electrical wires are connected and tight. Then I would have the transmission serviced if it hasn't been within the last 35,000 miles.

Have the trouble codes cleared and address the ones that return.

After that you may be looking at an internal transmission adjustment and/or repair.

Good luck.