KArthur

I got a 2009 HHR LS. After I start the car, I get three lights on the dash. Brake light, ABS light and TC light. I scanned it today and these codes came up:
U2105_00 : Lost communication with TCM
U2106_00: Lost communication with ECM
C0550_00 :ECU Performance
C0561_71 : System disabled information stored invalid serial data received

I tried clearing the codes, but they came right back after I restarted the car. Car starts and drives fine. No drivability issues.
The display on the dash says Service ESC and Service Traction Control.
When I cycle thru the DIC, the tire pressure displayed there is "- -" for three tires, so I know I need to replace the transmitter in the wheel.

Fuse #43 (ECM/Trans) fuse is good.
The car has been sitting for 2 or 3 years and there is a musky smell inside, so I know there has been some moisture in there. Carpet is not wet now though. One of the rear windows has a broken regulator and it was down about a 1/4in.

Any quick tips as to where to start?

Thanks

donbrew

Rodents chewing on wires?
Is this the same car as the one that won't shift to 3rd gear?
Tire pressure -- does not necessarily mean the transmitters are bad, could mean the receiver is not getting power along with all of those other modules.

KArthur

Yes. Same car, but it shifts fine. Wasn't the trans.
I've done a quick look at the wiring but didn't see anything wrong.

Oldblue

How’s the battery, low voltage can cause this problem, especially if it’s been sitting a while.

RJ_RS_SS_350

The moisture, I'd be looking at ground points.

donbrew

All of those codes indicate some sort of power problem; from wires, fuses, battery, grounds etc

PulpFriction

Start with the battery. Completely pointless trying to diagnose electrical problems with a bad one. If you get a parts store battery test, note the data but do not trust the clerk’s conclusions. A battery that tests marginally on a load test might be fine for quite awhile, but one that won’t take a charge or hold a solid 12.6V after several days or weeks, even when cold, will give probably you trouble.

KArthur

Hopefully I can get back on it next week. Battery on charge now. If that doesn't fix it, next step is to check fuse box for loose connections and make sure all the fuses/relays are seated. I found the ground on the left fenderwell (G1111 I think). Will check that also.

Oldblue

Have the battery load tested a couple of dead cells can indicate it’s a dead battery.
anything less then 12.4 volts is a dead battery to our beloved trucklets,
Are you trickle charging the battery while it’s in the HHR or did you take it out, clean the posts, pull the covers out and top up the fluid with distilled water?

KArthur

I pulled the battery out and put it on a charge. All the cells are full of water. I checked the voltage today and it is at 12.6 V. Did not get it load tested yet.

I pulled off the connector of the EBCM today to check voltages and ohms of the wheel sensors. The +battery voltage was 12.5v on pin 1 and 32. Pin 8 also had battery voltage. I also checked ohms between pin16 and a couple different points on the frame. It checked good (0.2 ohms). Next I checked ohms between the 4 different wheel speed sensors. 3 of them were open. The only one that gave me an ohm reading was LF sensors. This is the one I replaced a few days ago. Hopefully tomorrow I can do more testing and determine why the other three sensors are not reading.

I also re-seated all the fuses in the fuse box under the hood. All I have now is the CO550 DTC All three lights (brake, Anti-lock brake and Traction control) are ON.

Thanks