P1361

P1361 is GM's Ignition Coil Control Circuit Low — the ECM is commanding an ignition coil primary driver but the feedback voltage on the control circuit isn't pulling up the way it should during the dwell cycle, indicating an open or shorted primary control wire, a failed driver inside the ECM, or a coil with an internal primary winding failure. The ignition coil primary resistance on most LSx and Vortec coils measures 0.4-1.4 ohms cold, and the secondary measures 5,000-15,000 ohms; on the LB7/LLY/LBZ Duramax, the glow-plug control architecture uses similar primary-circuit feedback. Cheapest-first ladder: (1) Identify which specific coil the code points at (P1361 may be paired with a cylinder-specific extension code on some model years) and visually inspect the coil and its harness for chafe, oil contamination, or a melted boot. (2) Pull the coil connector and measure primary resistance pin-to-pin with a low-ohms meter — anything below 0.3 or above 2.0 ohms cold is suspect. (3) Wiggle-test the primary control wire from the coil back through the harness, especially at any harness-to-injector-harness branch point — chafe to a fuel-injector harness or to the cylinder head is a classic GM diesel failure. (4) Verify 12V feed at the coil with key-on (one pin should show battery voltage, the other is the ECM-driven trigger). (5) Swap the suspect coil with a known-good adjacent coil and clear the code; if the fault follows the coil, the coil is bad ($30-$80 LSx, $45-$120 Vortec). Don't replace the coil before inspecting the primary control wire for chafe at the injector harness on Duramax and at the valve cover edge on LSx — on the LB7/LLY/LBZ the ignition/glow-control wires bundle with the injector harness and a single chafed wire creates a P1361 that no coil swap will fix.

Vehicle-specific patterns: 2001-2007 Silverado HD / Sierra HD 2500/3500 with the LB7 / LLY / LBZ Duramax 6.6L diesel — the under-valve-cover injector harness is the famous failure point (LB7 in particular), and the same harness routes the glow-plug and primary control wires that throw P1361 when the insulation chafes through to the valve cover or the head bolts. 1999-2007 Silverado / Tahoe / Sierra with the LS-based Vortec 4.8/5.3/6.0 throws P1361 from primary spark plug wire failure on the early truck coils that still used short remote-mount plug wires (later trucks went coil-near-plug and the failure mode shifted to the coil itself). 2005-2010 Cobalt SS supercharged and 2008-2010 HHR SS with the LNF 2.0 Turbo throws P1361 when the coil-on-plug boots crack and arc to ground at the cam cover. The 2007 LBZ Duramax-to-2007.5 LMM transition introduced new emissions hardware and the primary control wiring routing changed; some early LMM trucks had a TSB-driven harness rework. Estimated repair: $60 (single LSx coil swap) to $1,800 (Duramax under-valve-cover injector + control harness on an LB7).