Gear Shift Actuator Circuit Open
What does P0940 mean?
The P0940 code means the vehicle's onboard diagnostic system has detected: Gear Shift Actuator Circuit Open. This is a critical severity code.
Common Symptoms
- Check Engine Light illuminated
- Transmission completely unable to shift
- Vehicle stuck in current gear or neutral
- Transmission warning light on
Probable Causes (Ranked by Likelihood)
- Failed gear shift actuator motor assembly Very High
- Open circuit in shift actuator main wiring harness High
- Connector failure at shift actuator assembly Moderate
- TCM shift output circuit board failure Low
Step-by-Step Diagnostic Procedure
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Inspect all shift actuator connectors for secure connection
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Measure resistance at the shift actuator motor terminals
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Test wiring harness continuity from TCM to shift actuator
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Attempt to command all shift positions with a bidirectional scan tool
Frequently Asked Questions
Is P0940 different from P0910 and P0920?
P0910 is specific to the gate select actuator, P0920 to the forward shift actuator, and P0930 to the reverse actuator. P0940 is a general code for the combined shift actuator assembly when it has an open circuit.
Can the vehicle be towed safely with the shift actuator failed?
Yes, but the transmission should be in neutral for towing. Some automated manual transmissions have an emergency neutral release procedure.
Is it worth repairing or should I replace the whole assembly?
If the actuator motor has failed, the entire actuator assembly typically needs replacement. Wiring repairs are worth attempting first as they are much less expensive.