Gear Shift Reverse Actuator Circuit High
Diagnostic trouble code P0927 indicates that the powertrain control module (PCM) or transmission control module (TCM) has detected a high voltage condition in the gear shift reverse actuator circuit. This means the electrical signal from the reverse gear actuator circuit exceeds the maximum expected threshold, preventing the module from properly controlling or verifying reverse gear engagement.
This code is considered high severity because it directly affects the transmission's ability to engage reverse gear. A vehicle without reverse capabilities can be unsafe to maneuver and may leave the driver stranded in certain parking situations.
Common symptoms
- Illuminated Check Engine Light
- Inability to engage reverse gear
- Transmission stuck in a forward gear or neutral
- Harsh or delayed shifting when attempting to select reverse
- Transmission enters limp mode
Likely causes
- Short to voltage in the gear shift reverse actuator wiring harness
- Faulty gear shift reverse actuator
- Corroded, damaged, or loose electrical connector at the actuator
- Internal transmission mechanical failure affecting the reverse shift mechanism
- Faulty Transmission Control Module (TCM) or Powertrain Control Module (PCM)
What to check before replacing parts
Scan for all stored diagnostic trouble codes and record freeze frame data.
Look for: Check if other transmission or electrical codes are present, which could indicate a broader electrical issue or shared ground/power supply problem.
Visually inspect the wiring harness and connectors leading to the gear shift reverse actuator.
Look for: Look for chafed wires, melted insulation, exposed copper touching power sources, or corroded pins inside the connector that could cause a short to voltage.
Test the voltage at the gear shift reverse actuator connector with a digital multimeter.
Look for: Verify if the voltage on the control circuit matches battery voltage when it should be grounded or at a lower reference voltage, confirming a short to power.
Perform a resistance test on the gear shift reverse actuator itself.
Look for: Compare the measured resistance of the actuator coil to the manufacturer's specifications; an out-of-spec reading indicates an internal fault in the actuator.
Check the TCM/PCM output signal to the actuator circuit.
Look for: Determine if the control module is commanding the high voltage or if the module itself has an internal short, which would require module testing or replacement.
This page explains the generic P0927 definition and is general reference information, not a diagnosis for your specific vehicle. Actual causes, severity, and repairs vary by make, model, engine, and mileage — always confirm with a scan tool and a qualified technician before replacing parts.
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