P0909 – Transmission gate select control error

Reinier

By Reinier (Contact Me)
Last Updated 2017-07-26
Automobile Repair Shop Owner

Trouble CodeFault LocationProbable Cause
P0909 Transmission gate select control error Mechanical fault

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What Does Code P0909 Mean?

SPECIAL NOTES: Non-professional mechanics are strongly urged NOT to attempt a diagnosis and/or repair of code P0909 – “Transmission gate select control error” without first reading the section in the manual for the affected application that deals with gear selection. Failure to gain at least a working knowledge of the gearshift mechanism and its control circuit will almost certainly result in confusion, a misdiagnosis, and quite possibly,  irreparable harm to the mechanism and its control system.

Also note that design specifics of components, as well as testing/diagnostic procedures for code P0909 vary greatly between applications and manufacturers. For this reason, the information in this guide is intended for general informational purposes only, and it should therefore NOT be used in any diagnostic procedure for this code on ANY application without making proper reference to the manual for the affected application. END OF SPECIAL NOTES.

OBD II fault codeP0909 is a generic code that is defined as “Transmission gate select control error”, or sometimes as “Transmission Shift Change Actuator Neutral Position Learned Value out of Range”. Regardless of the actual wording of the definition, this code is set when the PCM (Powertrain Control Module) detects a problem in the gear shift selector mechanism or its control circuit. Note that this code only applies to automated manual transmissions (also sometimes known as multi-mode transmissions), which are normal manual transmissions that have been fitted with automated, computer-controlled gear selection mechanisms.

While the design specifics of automated gear selection mechanisms vary between manufacturers, such systems usually consist of electrically or sometimes hydraulically operated actuators, control linkages/rods, position sensors, and input and feedback circuits.

In automatic mode, the PCM determines appropriate shift points based on input data from various engine and driveability sensors. When a shift point is reached, the PCM will actuate the clutch (which is a normal manual transmission clutch), and actuate the gear shift actuators to deselect the current gear, and then to select the desired gear ratio. Each de-selection/selection is monitored by position sensors, and should the PCM detect that the actual position of the gearshift mechanism does not agree with the desired position, it will set code P0909, and may also illuminate a warning light. Note that on some applications, multiple failure cycles need to occur before the PCM will illuminate a warning light.

The image below shows one example of the typical layout/construction of a gear shift mechanism. Note though that the appearance, construction, and operation of these mechanisms vary between manufacturers, and proper reference to the manual for the affected application MUST be made to determine the appropriate testing and possible repair methods that apply to that application.

Geaer Shift Actuator

What are the common causes of code P0909 ?

Some common causes of code P0909 could include the following-

  • Defective gear selection assembly
  • Defective position sensors
  • Defective actuators.
  • Incorrectly adjusted, or damaged control linkages
  • Mechanical failures in the transmission or clutch
  • Damaged, burnt, shorted, disconnected, or corroded wiring and or connectors
  • Failed or failing PCM. Note that this is a rare event, and the fault must be sought elsewhere before any control module is replaced

What are the symptoms of code P0909 ?

Some common symptoms of code P0909 could include the following-

  • Stored trouble code, and possibly an illuminated warning light
  • Additional transmission or clutch related codes may be present
  • Gear shifts may be harsh, erratic, or unpredictable
  • Transmission may be stuck in one gear, or some gears may not engage/disengage
  • Some clutch slippage may be present
  • Misfire-like symptoms may be present on some applications
  • Depending on the application and the nature of the problem, the transmission may not engage any gear

How do you troubleshoot code P0909 ?

Step 1

Record all fault codes present, as well as all available freeze frame data. This information can be of use should an intermittent fault be diagnosed later on.

NOTE: If additional codes are present, note the order in which they were stored, and resolve codes that precede P0909 first and especially if any additional codes refer to the clutch actuator or clutch position sensor.  Failure to do this could result in a misdiagnosis and possibly in the unnecessary replacement of parts and components.

Step 2

Refer to the manual to locate the gear shift mechanism, and inspect it and all related components for signs of damage, water intrusion, or other visible defects. Check all electrical connectors for tightness and condition. Replace any connector(s) that is in a less than perfect condition.

If any component that is associated with the gear selector mechanism is found to be damaged, replace the components with OEM replacements to ensure proper operation.

Step 3

Inspect all associated wiring- look for damaged, burnt, shorted, disconnected, or corroded wiring and/or connectors. Replace wiring or make repairs as required if damaged wiring is found.

Step 4

If no damage to wiring or any components is found, prepare to perform continuity, resistance, ground integrity, and where applicable, reference voltages tests on all associated wiring, but be sure to disconnect all wiring from the PCM to prevent damaging the controller during resistance tests.

WARNING: DO NOT test any circuit if you are not sure what that circuit does, or how it works. ALWAYS refer to the manual to determine the function of each circuit, as well as the color coding of each wire in each circuit. Failure to do this will result in a misdiagnosis, wasted time, and the unnecessary replacement of expensive parts and components.  

Pay particular attention to the circuits that relate to position sensors, as well as the internal resistances of all position sensors, since a resistance value is a reasonably good indicator of that sensor’s overall condition. Replace all position sensors with OEM parts whose internal resistance does not match the value stated in the manual for that sensor very closely, and preferably exactly.

Step 5

If all electrical values check out, use the scanner to activate all actuators multiple times to rule out intermittent faults. Monitor the status of each actuator as it is activated, and replace those that are slow to react, or do not react at all.

Note that in some cases, some or all actuators are incorporated into a single the gear shift mechanism assembly, which may also house one or more position sensors. In these cases the better option is to replace the entire assembly since repairs are either not cost effective, or possible.

Step 6

Clear all codes once all repairs are complete, and operate the vehicle normally for at least one complete drive cycle to see if the code returns. If the code does return, suspect an intermittent fault, or a defective PCM. Note however that an intermittent fault is the more likely problem, so repeat all electrical tests until the problem is found and repaired, or refer the vehicle to a competent repair facility or the dealer for professional diagnosis and repair.

NOTE: on most applications it is required to perform relearning procedures when parts and components relating the gear selection mechanism are replaced. Refer to the manual for the application for details on how to perform required relearning procedures successfully. Note that these procedures can be tricky at times, so seek professional assistance if the fault persists after performing all required procedures. 

Codes Related to P0909

  • P0904 – “Gate Select Position Circuit”
  • P0905 – “Gate Select Position Circuit Range/Performance”
  • P0906 – “Gate Select Position Circuit Low”
  • P0907 – “Gate Select Position Circuit High”
  • P0908 – “Gate Select Position Circuit Intermittent”

NOTE: While the codes listed above are not strictly related to P0909 “Transmission gate select control error”, these codes can set as a result of P0909, or they can contribute to code P0909 setting.

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