1997 Jetta GL 5-Speed: P0411 Secondary Air Injection System Flow Fault Diagnosis

I have a 1997 Jetta GL with a 5-speed manual transmission and a 2.0L engine. The Check Engine Light (CEL) came on with fault code P0411, indicating an incorrect flow in the secondary air injection system (SAI). I've already tested the kombi valve — it functions properly, opening and closing as expected while maintaining vacuum. Vacuum is confirmed at the firewall block that activates the kombi valve. The SAI pump itself has been inspected and does not appear to be working. When I bypassed the pump with a battery jump, there was no response, indicating the issue may lie in the electrical circuit rather than the pump unit. I replaced the relay and the strip fuse located behind the driver's headlight, and all fuses checked out as good. I have power at terminal #111 on the relay (where two wires connect to the fuse strip), but no ground connection. However, there is a ground present at the pump plug connector — yet no power from the ignition system when the key is turned on. I've traced the wiring from the SAI pump plug as far as it connects with a larger bundle of wires, which then disappears beneath the battery tray. I suspect a broken wire or an intermittent connection in that area, but I'm unable to pinpoint the exact location. Any advice or troubleshooting steps for this P0411 issue on a 1997 Jetta would be greatly appreciated.