Error Code P0926 is defined as Gear Shift Reverse Actuator Circuit Low. This is a generic trouble code, meaning it applies to all vehicles equipped with the OBD-II system, especially those made since 1996 up to the present. Specifications on the definition, troubleshooting, and repairs, of course, vary from one make and/or model to another.
The gear shift reverse actuator is a critical part of an automatic transmission and is responsible for actuating the shift into a reverse-moving gear.
When this code appears, it means the ECM (engine control module) has determined a problem in the operation of the gear shift reverse actuator of the transmission. This is the component that controls how a vehicle’s transmission shifts into reverse gear.
To put it simply, the ECM has found a signal that indicates the voltage in the gear shift reverse actuator is lower than the normal parameters set by the vehicle’s manufacturer.
This voltage anomaly may be caused by improving guide rail function or shift shaft that corresponds to the transmission’s reverse gear, making it problematic or impossible to shift the transmission into reverse gear.
- Harsh shifting
- Vehicle unable to shift to forward gear
- Increased fuel consumption
A mechanical problem within the transmission likely causes this code. Other possible causes include:
- Defective gear shift reverse actuator
- Defective connectors or wirings
- Defective gear guide rail
- Faulty shift shaft
- Faulty PCM or TCM (rare)
How to Check
As with most error codes, diagnosing this code requires an advanced scanner and a digital volt/ohmmeter (DVOM).
When diagnosing, make sure to address the codes in the order that they were stored. Download the freeze frame data and all stored trouble codes.
Start the diagnosis by checking all the connectors, wirings, and related components for damage.
Next, clear the error code and see if it comes back. If the code comes back, check the voltage and ground signal at the gear shift actuator switch using the DVOM.
If there is no voltage or ground signal detected, disconnect the PCM and related modules to test the continuity between the battery ground and gear shift actuator switch.
Next, inspect the shift shaft and the forward guide rail. Look for any signs of damage. Make sure both work correctly.
Then, clear the codes and see if they come back. If the code still comes back, use the DVOM and check the TCM for any fault and continuity.
If the TCM is okay, then proceed by checking the PCM for continuity.
Lastly, clear the error code and retest to see if it returns.
How to Fix
- Replace bad or damaged connectors, wirings, or any components
- Replace faulty gear shift forward actuator
- Repair or replace defective shift shaft
- Repair or replace forward gear guide rail
- Replacement of transmission as a whole
- Replace faulty PCM or TCM
The most common mistake in diagnosing this code is not clearing the codes in the order they were stored. In addition, some mechanics proceed with replacing perfectly good components.