P0940 critical

Gear Shift Actuator Circuit Open

The P0940 code means the vehicle's onboard diagnostic system has detected: Gear Shift Actuator Circuit Open. This is a critical severity code.

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Keep driving?: No -- stop driving
DIY difficulty: hard
Estimated cost: $400 - $2,000 (parts and labor)

Check Your Fluid First

ANCEL AD310 OBD-II Scanner

Read and clear transmission codes. Many trans codes are caused by low or burnt fluid -- check level and color before assuming the worst.

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Read Transmission Codes

LAUNCH CRP123X (Reads All Systems)

Basic scanners only read engine codes. This reads transmission, ABS, and airbag too.

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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

Inspect all shift actuator connectors for secure connection
Measure resistance at the shift actuator motor terminals
Test wiring harness continuity from TCM to shift actuator
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.