Possible causes

– Faulty Reverse Inhibit Solenoid
– Reverse Inhibit Solenoid harness is open or shorted
– Reverse Inhibit Solenoid circuit poor electrical connection

When is the code detected?

When the Reverse Inhibit solenoid energizes, the operator can shift the transmission into reverse. The Powertrain Control Module (PCM) enables the Reverse Inhibit solenoid whenever vehicle speed is below 5 mph. When the vehicle speed is above 5 mph, the PCM de-energizes the solenoid, which prevents the operator from shifting the transmission into reverse.

Symptoms

– Engine Light ON (or Service Engine Soon Warning Light)

P0801 BUICK Description

An ignition voltage is supplied to the Reverse Inhibit solenoid. The Powertrain Control Module (PCM) controls the solenoid by grounding the control circuit via an internal switch called a driver. The driver supplies the ground for the component being controlled. Each driver has a fault line which the PCM monitors. When the PCM commands a component ON, the voltage of the control circuit should be low (near 0 volts). When the PCM commands the control circuit to a component OFF, the voltage potential of the circuit should be high (near battery voltage). If the fault detection circuit senses a voltage other than what is expected, the fault line status changes causing the P0801 code to set.