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2007 Chevrolet Tahoe 5.3L Misfire P0300-00, P0575-00, U0073-00, U0100-00, C0561-71 - Load-Induced Power Loss and Stabilitrack Activation

Model: 2007 Tahoe Fault Code: C0561 Posted: 2019-09-23 19:05

Good evening everyone, I own a 2007 Chevrolet Tahoe with a 5.3L V8 engine, currently around 200,000 miles. The vehicle is exhibiting multiple diagnostic trouble codes: P0300-00 (random misfire), P0575-00 (fuel pressure issue), U0073-00 (loss of communication between ECM and TCM), U0100-00 (loss of communication with the transmission control module), and C0561-71 (cylinder 7 misfire). Symptoms are intermittent but severe under load. When I start the engine and let it warm up, I can drive at very low throttle for extended periods without issues. However, as soon as I apply significant throttle, the check engine light begins flashing, the Stabilitrack warning light activates, and there is a noticeable loss of power. Misfire data consistently shows cylinder 7 as nearly dead—sometimes accompanied by cylinder 2 or 8. After the condition worsens, the doors may lock intermittently on their own, and the speedometer occasionally tics or fluctuates. I have already replaced the fuel injector, coil pack, plug wire, and spark plug for cylinder 7. All engine grounds (including under the driver’s side door) have been cleaned thoroughly. I’ve disconnected and reconnected all connectors from the ECM, TCM, and BCM—no visible damage or loose pins. The wiring harnesses appear intact with no exposed wires or fraying. Fuse box connections are secure. Despite these efforts, the issue persists. I've been troubleshooting this for months. Background: We purchased the vehicle five months ago. Initially, it had rare misfire events—once per month—that would resolve on their own. Over time, frequency increased. After running low on oil, one of the AFM lifters collapsed; replacing it improved performance temporarily but didn’t eliminate the issue. Subsequently, fuel pump sending unit lines rusted and failed—I replaced that component, which allowed normal operation for only a couple of days before the current misfire problem emerged. The vehicle is now essentially undriveable under heavy load. I cannot reproduce this behavior in the garage—it only manifests when throttle demand increases. I'm at a loss as to what to investigate next. Any insights or suggestions would be greatly appreciated. Thanks in advance for your help.

Related fault codes
C0561P0300P0575U0073U0100
Comments (3)
Anonymous 2019-09-24 06:28

Start by diagnosing communication issues—focus on U0073-00 first, as it indicates a loss of data between the ECM and TCM. Ensure no devices are left plugged into the DLC (Data Link Connector), as this can interfere with signal integrity. Avoid connecting any additional electronics to the DLC unless absolutely necessary.

Anonymous 2019-09-24 15:48

No external electrical devices have been connected. The only device used is my MS906BT scanner, which consistently establishes communication every time I connect it. The vehicle always starts reliably and the scan tool reads all data properly. I’ll inspect the wiring harnesses upon returning home—thank you for the advice.

Anonymous 2019-09-24 17:27

The harnesses appear in good condition overall. There is a slight indentation in the insulation of one wire on the passenger-side harness, but it does not penetrate through the outer layer. I have taped this area securely with 3M Super 33 tape to prevent further damage.