Code result
P0642
Sensor Reference Voltage \"A\" Circuit Low
High severity
What it means
The 5 V reference voltage on the A circuit (used by multiple sensors) is below threshold — short to ground or excessive current draw by a single sensor pulling the rail down.
Is it safe to drive?
No — stop driving
This code can put the vehicle into limp or reduced-power mode. Avoid extended driving and have the vehicle diagnosed promptly.
Most likely causes
Sensor or harness shorted to ground
highOne of the most commonly reported causes for this code — check this first.
ECU reference output damaged
lowLess common, but worth ruling out after the more likely causes.
Connector pins corroded - high contact resistance
lowLess common, but worth ruling out after the more likely causes.
Related help
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