P0776

Symptoms

• Check engine light with stored code
• harsh
• erratic
• or delayed shifts
• transmission slipping under load or stuck in one gear
• possible limp mode
• engine may stall during deceleration (torque converter related)
• mechanical noises (whining, grinding, rumbling)
• metal wear particles in the transmission fluid in advanced cases.

Probable causes

• Defective or stuck pressure control solenoid B
• low
• dirty
• degraded
• or incorrect-type transmission fluid
• damaged
• corroded
• or disconnected wiring/connectors in the solenoid circuit
• internal transmission failure causing hydraulic blockages
• pressure pump failure
• PCM/TCM failure (rare).

Diagnostic steps

1. Record all fault codes and freeze frame data with a scanner capable of reading transmission data.
2. Check transmission fluid level and condition; if low, inspect for leaks; if burnt or contaminated, service the fluid (and filter) and retest.
3. Inspect the wiring harness and connectors to the solenoid for damage or corrosion.
4. Perform resistance and continuity checks on the external harness, then on the transmission internal wiring.
5. With a scan tool, command the solenoid to cycle and watch live data - the TCM output should pulse from 0 V (off) to about 12 V (fully on).
6. Attach a pressure gauge at the correct test port and compare line pressure to service manual specifications.
7. If the solenoid is faulty or stuck, replace it (OEM part), refill fluid, and retest.
8. If the problem persists, inspect the oil pan for wear particles and address internal transmission issues; consider TCM only as a last step.
9. Confirm P0776 does not return after a road test.