B1000

B1000 — ECU defective (also seen as ECM internal performance, module internal failure depending on manufacturer) — is one of the few codes where the module itself is actually the most likely cause, but it is still worth ruling out the cheap stuff first because power, ground, and communication faults can mimic an internal-failure code. Cheapest first: clear it, drive, see if it returns immediately or after a delay. Check ALL module power feeds with a meter (every fuse the module touches, plus the keyed-on supply), and verify every ground stud and pin is clean and tight — a corroded ground at the inner fender or behind the headlight assembly can cause a module to self-diagnose as defective. Watch communication on the CAN/LIN bus with a bidirectional scan tool: if the module shows up in the scanner's module list and responds to ID requests, it is alive enough to be talked to, and an internal-failure code is more credible. If it does not show up at all, the fault is more likely wiring or power. Voltage at the module's main connector key-on should be within 0.3V of battery, and ground-side voltage drop under load should be under 0.1V. The expensive misdiagnosis: ordering a $400-$1,500 replacement module before checking the $0 power and ground, then finding out the new module sets the same code in 30 seconds because the actual fault was a chewed harness.

Vehicle-specific patterns: 2003-2007 Ford F-150 — GEM (Generic Electronic Module) sets B1000 after water intrusion at the cowl drain; dry, clean, and seal often recovers. 2005-2010 Chrysler 300/Dodge Charger — TIPM (Totally Integrated Power Module) internal failure is a well-documented pattern, often requires TIPM replacement. 2007-2012 Hyundai/Kia — BCM internal fault after battery jump-start with reversed polarity. 2006-2011 Honda Civic — driver door multiplex unit fails and sets module-internal codes across the bus. Estimated repair: $0 to $1,800.