Possible Causes

WARNING: This page is about a different car, the 2003 Mazda 6. However, it is still accessible from the selected car via links, so may be relevant.

Possible causes are:

Clutch switch malfunction
Open circuit in Black wire between ground and clutch switch 5-pin harness connector terminal "D"
Open circuit in White/Green wire between clutch switch 5-pin harness connector terminal "B" and PCM 30-pin harness connector terminal "1R"
PCM malfunction
Poor connection of clutch switch or PCM harness connectors.
Short to ground in White/Green wire between clutch switch 5-pin harness connector terminal "B" and PCM 30-pin harness connector terminal "1R"