What P0966 means
Pressure control solenoid B circuit low, meaning a short to ground in the driver circuit.
How the engine computer detects it
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.
Written from public technical sources and not yet checked by a mechanic. How we write these pages
Symptoms
- MIL on immediately
- Limp mode with reverse and one forward gear
- No torque converter lock-up, higher fuel consumption
Common causes
- Chafed control wire touching ground Most likely
- Internally shorted solenoid in the valve body assembly Possible
- Fluid or moisture in the connector Possible
- Faulty output stage in the control module Less likely
How to diagnose P0966
- Read every stored code with an OBD-II scanner. If misfire or fuel trim codes are there too, fix those first: they often cause this one.
- Inspect the parts involved: pressure control solenoid b, wiring harness, tcm.
- Work through the causes above from most to least likely, cheapest checks first.
- Clear the code and drive a full drive cycle to confirm the repair held.
Reading the code
- P
- Powertrain
- 0
- Generic (SAE) code
- 9
- Transmission
- 66
- Specific fault
Questions drivers ask
Can I drive with code P0966?
Drive gently and only as far as you need to. The engine computer may limit power to protect the engine, so avoid highways and heavy traffic until it's fixed. If the check engine light starts flashing, pull over.
Will my car pass an emissions inspection with P0966?
Probably not in states that test vehicles with an OBD-II scan: an emissions-related code that keeps the check engine light on is usually an automatic fail. Rules differ by state and county, so check yours.
This page is general information, not a substitute for a professional diagnosis. Repair costs are rough estimates for parts and labor and vary by vehicle and region.