So, this is my friends HHR and he is having an issue that is causing the guages to drop to 0 and cone back to working, as well as all of the lights go through their startup cycle. Like if i start the car, i expect all the lights to be on for a second and turn off shortly after (i assume as like a self check). Well his tries, but seems to lose power and start the process again before it can ever finish. If i do not start the car but have the key on, all works, if i start the car, it randomly starts doing it. I have to assume it is a loose connection somewhere but do not know enough of the common issues. I have a tech2 and will list all of the codes i retrieved from all the different systems. They seem to tell a tale of an unstable can bus. Any suggestions on where to start this project. It drives alright but kind of lacks power and i think its having a hard time shifting to 3rd but probs unrelated.

Codes:

U2108 B1325 U2107 U2100 B3935 B3060 B1370 U0140 U0121 U0100 U0073 P0300 P0700 P0575

 

Did you tighten the bolts in the under hood fuse box, the need to be really cranked down? Not just tight, the connectors under it need to engage.
The problem is NOT the CANbus, as scary as that is, it is a power problem. If a module is not getting power all of the downstream modules lose communication.
Here is a youtube to help figure out which module is have power trouble.

 

X2 tighten the four bolts in the under hood fuse box and load test the battery, 12.4 volts static and under isn’t enough to power the computers and recharge the battery

 

So i did check those before as i did ALOT of looking into this issue recently. I didnt give them my gorilla muscle but they seemed really good. I have seen a lot of posts mentioning the fusebox in general so next time im with the vehicle i will give it another go. Feel free to let the other suggestions fly tho as it is a week or so between visits.

 

Check the ground points make sure they are clean and tight.

 

Ok and to make sure i check all correctly, when its said to check the FB "halves", is that just the clips around the sides of the box??

 

any list or locations to impotant ground locations?

 

The 4 bolts inside the box.
Unplug, inspect and replace all of the module connectors; ECM, TCM, EBCM, BCM. (Engine control, transmission control, brake control, body control) Sometime pins in the connectors get pushed out the back.
Push all of the fuses in both fuse boxes to ensure good contact.
What happened before this started? Any work done, any after market installations?

 

https://www.chevyhhr.net/forums/how-...cations-56504/

Like this one.

 

Ok, so i tightened down the 4 bolts which i DID NOT do before, I misunderstood what bolts were referenced before. The flickering if the guages seemed to go away and it also seems as the BCM was able to complete its bootup finally. Now the issue i am seeing is the ABS, T/C, and BRAKE light come on and then go away. No specific paytern like only when turning or stopping. No new codes atm, just less of the communication failures.