OBD-II Generic Error Code P0977: How to Fix It

Q: Can I drive my car with a P0977 code?

You can drive short distances, but it is not recommended. P0977 often triggers limp mode, which limits your transmission to one or two gears to prevent damage. Continuing to drive with this code can cause accelerated wear on the transmission and potentially lead to a complete transmission failure if the root cause is not addressed promptly.

Q: What is the most common cause of code P0977?

The most common causes are a faulty or shorted Shift Solenoid B, damaged or corroded wiring and connectors in the transmission harness, low or degraded transmission fluid, or a poor ground connection. In rarer cases, a failing Transmission Control Module (TCM) can also trigger this code.

Q: How much does it cost to fix error code P0977?

Repair costs vary widely. Cleaning a corroded connector or replacing a ground strap may cost under $50 in parts. A transmission fluid service typically runs $100–$200. Replacing a shift solenoid or solenoid pack can cost $150–$400 in parts alone, with labor adding $200–$500 depending on the shop and vehicle. TCM replacement is the most expensive repair, often ranging from $500 to $1,500 or more.

Q: Will replacing the transmission fluid fix P0977?

In some cases, yes. Dirty or low transmission fluid can cause solenoids to stick or generate erratic voltage signals. A fluid service is always a good first step and low-cost diagnostic measure. However, if the solenoid itself or the wiring is physically damaged, a fluid change alone will not resolve the code.

Q: What other codes are related to P0977?

P0977 is part of a family of shift solenoid codes. Related codes include P0973 and P0974 (Shift Solenoid A circuit low/high), P0976 (Shift Solenoid B circuit low), P0978 through P0985 (covering shift solenoids C through F), and P0700 (Transmission Control System malfunction, a general indicator). If multiple solenoid codes appear together, a wiring harness fault or TCM issue is more likely than multiple failed solenoids.

Abstract

Error code P0977 indicates that your vehicle's transmission control module (TCM) has detected a higher-than-normal voltage signal in the Shift Solenoid B control circuit. Shift solenoids are small electrically-operated valves inside the transmission that manage gear changes by controlling hydraulic fluid flow. When this circuit reads an abnormally high voltage, the TCM can no longer trust the solenoid's operation, which may cause harsh shifting, gear slipping, or the transmission getting stuck in a single gear.