P0973

P0973 means the TCM has commanded shift solenoid A on, expected to ground its control circuit through the solenoid coil, and instead seen the circuit voltage stay low when it shouldn't be — typically a short to ground on the control wire or a coil shorted internally so it draws excessive current. P0973 is an electrical-only fault: the TCM detected the problem on the wire/coil side without needing to see a gear-ratio mismatch. Cheapest-first ladder: (1) Pan-drop and ohm shift solenoid A across the coil — expected resistance is 8-30 ohms at room temperature on most domestic shift solenoids; a reading under 5 ohms means the coil is shorted internally. (2) Disconnect the case connector and check whether P0973 returns with the solenoid out of circuit — if the code persists, the short is upstream in the harness or the TCM driver. (3) Inspect the internal harness lead frame and the case connector pins for chafing, melted insulation, or fluid intrusion — automatic transmission fluid wicking into a damaged harness shorts the control wires to ground exactly like a shorted coil. (4) Use a scope on the control wire to capture the commanded pulse — a healthy driver pulls the line cleanly to ground when commanded and releases it cleanly when not; a stuck-low pulse confirms a TCM driver fault rather than a solenoid fault. Expensive-misdiagnosis caveat: a single shorted solenoid can damage the TCM driver that controls it, so replacing only the solenoid on a P0973 that has been running for thousands of miles sometimes leaves a wounded TCM that fails 5,000 miles later — verify driver health before signing off on the repair.

Vehicle-specific patterns: GM 4L60E is the textbook P0973 platform — shift solenoid A controls the 1-2 shift (descendant of the 700R4 1-2/3-4 architecture) and the solenoid is a known wear item; coil shorts are the most common cause and the solenoid is a sub-$50 part with the pan already off. Ford 4R70W / 4R75W sees P0973 from SS-A coil failure and from harness chafe at the case pass-through grommet. Chrysler 545RFE / 45RFE sets P0973 as part of the solenoid pack — the pack is replaced as a unit rather than individual solenoids, which raises parts cost but reduces labor risk on internal harness damage. 2007-up GM 6L80 throws P0973 from harness chafe at the valve body bolt locations where the lead frame routes past sharp casting edges. Estimated repair: $300 to $2,200.