P0747: Pressure Control Solenoid A Stuck On

What does P0747 mean?

Pressure control solenoid A sets line or clutch pressure by current; most are 'normally high', so with no current – as in limp mode – maximum pressure applies. 'A' is usually the line pressure valve, on GM clutch-to-clutch transmissions (6T, 8L, 9T) the pressure valve of clutch 1. Ford does not use P0745–P0749 but P0960–P0963. P0747 means the valve is electrically fine but pressure stays applied. On GM's clutch-to-clutch units the off-going clutch 1 does not release – slip stays below 50 rpm (9-speed, 0.8 s on loaded downshifts), and Allison flags 25 rpm or less for 0.3–1 s, both after one trip. On line pressure valves it means permanently high pressure. Harsh, abrupt shifts, a tied-up transmission and a default gear follow. GM noted false settings on 2017 8-speeds: clear and retest first.

The code tells you which monitor failed, not which part is broken. Test before replacing parts.

Symptoms

• Harsh, abrupt shifts
• Transmission ties up, engine speed drops on shifts
• Limp mode or default gear
• Check engine light

Common causes

• High Pressure or clutch valve or spool sticking (dirt, debris)
• Medium Valve body worn
• Medium Software or false setting
• Medium Wrong or contaminated fluid
• Low Clutch plates stuck or burnt

Likelihood is a general estimate across vehicles; your make and model may differ.