P0966: Pressure Control Solenoid B Control Circuit Low

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.

Medium severity. Can I keep driving?Drive as little as possible and gently. If the transmission slips or stays in one gear, go slowly to a repair shop or call for a tow truck.

Symptoms

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

Most likely causes

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

What to check, in order

Start with the simplest. You can tick off each step.

Check the fluid level and condition according to the manufacturer
With the connector unplugged, check whether the signal wire is making contact with ground.
Check the transmission connector
Read the data with a transmission-compatible scanner
Measure the solenoid valve circuit
Leave opening the transmission to a specialized repair shop

Good to know

Repair difficulty: hard
It can trigger limp mode.
It affects emissions.

What each character of P0966 means

P: Powertrain: engine and transmission
0: Generic code: same on every make
9: Transmission
66: Specific fault in that system

Frequently asked questions

Can I keep driving with code P0966?

Drive as little as possible and gently. If the transmission slips or stays in one gear, go slowly to a repair shop or call for a tow truck.

What causes code P0966?

The most common causes are: chafed control wire touching ground; internally shorted solenoid in the valve body assembly; fluid or moisture in the connector.

Related codes

Sources

Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.