Code result
P077C
Output Shaft Speed Sensor Circuit Low
High severity
What it means
Output shaft speed sensor signal voltage below the lower limit — short to ground or open supply. TCM disables vehicle-speed dependent shift logic and may force limp-home.
Is it safe to drive?
No — stop driving
This code points to a problem that can cause damage or affect safety. Avoid driving and have the vehicle diagnosed promptly.
Most likely causes
Signal wire shorted to ground
highOne of the most commonly reported causes for this code — check this first.
Connector pins corroded - high contact resistance
lowLess common, but worth ruling out after the more likely causes.
Harness chafing through insulation
lowLess common, but worth ruling out after the more likely causes.
Related help
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