Causes

If you've had the OBD-II diagnostics code P1700 in a manual transmission Nissan, you've probably heard or felt grinding in neutral. If the sound improves with the clutch depressed, there's likely major damage to the transmission. If your vehicle is an automatic or there aren't noticeable signs besides the dashboard light, there's a greater chance that only a smaller part of the transmission is damaged.

Significance

The P1700 code has a reputation for revealing two outcomes: either the transmission has massive problems and needs either major repairs or complete replacement, or there is little wrong and the car needs its transmission flushed and a general tune-up to run better and clear the diagnostics code.

Solutions

Transmission repair and replacement can be some of the costliest work performed on a vehicle, so investigate other options before proceeding unless a professional mechanic is certain the transmission is ruined. New tranny fluid and a replacement clutch may fix the problem, so consider those actions first. Then disconnect the battery for 30 seconds and drive the car for 100 miles to see if the "check engine" light reappears on the dashboard.