P1689

P1689 indicates a fault on the Delivered Torque output circuit between the PCM and the EBCM/TCS (traction control) module — the PCM publishes a calculated engine torque value over the serial data bus or, on older platforms, over a dedicated PWM circuit, and the traction control module uses this value to decide spark/fuel cuts during wheel slip. P1689 sets when the EBCM detects the torque signal is missing, frozen, or out of physical range (e.g., reporting 600 Nm at idle). Diagnose cheapest first: pull codes from the EBCM, not just the PCM — if you see U-codes pointing to lost communication with the PCM, fix the bus issue first. If communication is healthy, scan-tool the Delivered Torque PID at idle (should read 30-80 Nm depending on accessory load) and snap-throttle to confirm it moves toward 200-300 Nm momentarily. If the PID is frozen at a value or absent from the data stream, the PCM's torque-model output is faulty (often a calibration mismatch after a salvage PCM swap) or the bus segment between PCM and EBCM is degraded. The expensive misdiagnosis: replacing the EBCM at $800+ when the actual fault is a mismatched PCM calibration that needs a $0 reflash to the correct part number.

Vehicle-specific patterns: 2003-2007 Silverado/Sierra/Tahoe/Yukon/Suburban 4.8L/5.3L/6.0L with StabiliTrak is the most common P1689 platform — when a PCM is replaced with a salvage unit, the torque-output calibration doesn't match the EBCM's expected range. 2005-2009 Trailblazer/Envoy 4.2L I6 sees P1689 from intermittent class-2 bus dropouts caused by a failing under-seat splice pack. 2007-2010 Suburban/Yukon XL 5.3L/6.0L throws P1689 alongside knock-sensor codes when the under-intake knock sensor harness shorts and the PCM's torque model goes invalid — this is the classic LS truck knock harness failure (TSB 07-06-04-032). 2008-2012 Acadia/Traverse/Enclave 3.6L LY7 sets P1689 from internal EBCM failure. Estimated repair: $90 to $1600.