P0974

P0974 is the high-side counterpart to P0973 — the TCM commanded shift solenoid A on, expected the control circuit voltage to drop, and instead saw it stay high when it shouldn't be. The fault means either the solenoid coil is open (no continuity), the control wire is broken or shorted to a power source, or the TCM driver has failed in the high state. Like P0973, this is electrical-only — the TCM didn't need to see a gear-ratio fault to set the code. Cheapest-first ladder: (1) Pan-drop and ohm shift solenoid A across the coil — an open coil reads infinity and is the cheap answer; expected resistance is 8-30 ohms at room temperature. (2) Disconnect the case connector and use a DMM in continuity mode to check the control wire from the TCM connector to the case connector pin — an open wire is a common P0974 cause on transmissions that have been worked on previously (pinched harness, broken pin at a hand-built splice). (3) Backprobe the control wire and check for unexpected battery voltage with the key on, TCM not commanding — voltage on a wire that should be open means a short to power upstream. (4) If the solenoid coil, wire, and TCM driver all check out, inspect the case connector for backed-out pins or contaminated terminals — fluid intrusion at the case connector is a recurring source of intermittent and then hard-set P0974. Expensive-misdiagnosis caveat: an open solenoid coil and a broken control wire produce identical scan-tool data; spending an hour on harness diagnostics on a transmission where the coil is simply burned out is the classic time-waster — ohm the coil first.

Vehicle-specific patterns: GM 4L60E sets P0974 from SS-A coil burnout in the same wear window as P0973, often after long periods of operation with burnt fluid that has cooked the solenoid coil insulation. Ford 4R70W / 4R75W throws P0974 from SS-A open-coil failure and from harness damage at the case connector after fluid contamination. Chrysler 545RFE sees P0974 as a solenoid pack open-circuit failure — pack replacement is the standard fix. 2008-up GM 6L80 throws P0974 from internal harness damage at the lead frame and from open-circuit pin failures at the case pass-through connector. Estimated repair: $300 to $2,200.