P0966: Pressure Control Solenoid B Control Circuit Low

What does P0966 mean?

Pressure control solenoid B circuit low, meaning a short to ground in the driver circuit. On GM's six-speeds and the Saab 9-4X 6T70, B is clutch pressure solenoid 2 for the 3-5-reverse clutch; a short lasting 0.3 s (GM 2018 table) or 1 s (Saab) sets a Type A code with a fixed limp mode: reverse and 5th gear, maximum line pressure, converter clutch off. GM's 8-, 9- and 10-speeds use B for a clutch solenoid and treat less than 0.5 ohm as a short; Allison 1000 uses it for pressure control solenoid 2 with ground-short detection in 125 ms. Ford does not use the B codes. Siblings are P0964 open, P0967 high and P0965 performance; solenoids A and C follow the same scheme.

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

Symptoms

• MIL on immediately
• Limp mode with reverse and one forward gear
• No torque converter lock-up, higher fuel consumption

Common causes

• High Chafed control wire touching ground
• Medium Internally shorted solenoid in the valve body assembly
• Medium Fluid or moisture in the connector
• Low Faulty output stage in the control module

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