Gear Shift Actuator Temp Too High
This code indicates that the PCM has detected a gear shift actuator temperature that exceeds a predetermined limit. When this occurs, a code is stored and a malfunction indicator may be illuminated. Some (automatic and automated manual transmission equipped) vehicles will also place the transmission controller in “limp-in” mode. Limp-in mode will allow maximum fluid pressure to reach the valve body and may cause harsh shifting.
Code Set Parameters
Gear shift actuator temperatures that exceed a predetermined limit, set by the vehicle manufacturer, will cause a code to be stored in the PCM and possibly a service engine soon lamp to be illuminated.
A service engine soon lamp is usually accompanied by the distinctive smell of overheated friction material. Smoke from the bell housing area is also possible, as is clutch slippage, and/or a lack of transmission disengagement/engagement.
Common causes include clutch hydraulic malfunctions (caused by a hydraulic fluid leak), a worn out clutch/clutches, a faulty clutch actuator temperature sensor, transmission fluid temperature sensor, an overheating engine, or defective PCM. When this code is set, it is imperative that the gear shift actuator mechanism, clutch, and clutch actuator mechanism be checked prior to further vehicle operation.
Misdiagnosis may range from one extreme to the other. Often, when this code is stored, a problem is incorrectly diagnosed as a worn or defective clutch friction plate, pressure plate, or throw-out bearing when a hydraulic fluid leak, clutch actuator mechanism, or gear shift mechanism are at the root of the problem.
- Some modern manual and automated manual transmissions are equipped with a gear shift actuator temperature sensor (usually a two-wire variable resistance sensor) which provides the PCM with data
- The gear shift actuator sensor is typically mounted in the vicinity of the shifter linkage opening of the transmission and an estimated gear shift actuator temperature is programmed into the transmission controller or the PCM
- The sensor has a voltage wire (typically it is a 5-volt reference signal) and a ground wire
- The PCM uses the reference voltage wire to monitor gear shift actuator temperature
- As gear shift actuator temperature increases, sensor resistance decreases and reference voltage increases
- When the gear shift actuator is cool, sensor resistance is high, driving reference voltage to the PCM down
- The PCM receives input reference voltage readings as gear shift actuator temperature and reacts accordingly
- If gear shift actuator temperature is excessive, a code is stored and a service engine soon lamp may be illuminated.
If the gear shift actuator over temp code is set and the engine is not overheating, then it is very likely that a low or substandard hydraulic fluid condition, low transmission lubricant condition, or a worn clutch plate condition is present
- To perform a thorough diagnosis, any leaks should be repaired and the related system should be filled with the proper amount and type of fluid
- The clutch and gear shifter should then be operated normally and rechecked
- However, leaks that originate from inside the bell housing will likely require removal of the transmission, at which time you may want to consider a clutch, pressure plate, and throw-out bearing replacement if the mileage dictates
- Flywheel resurfacing is also recommended with a clutch replacement.
If the gear shift mechanism and transmission both appear to be in good working order and don’t appear to be overheating or leaking, suspect a faulty gear shift actuator temperature sensor
A scanner or code reader, a digital volt ohmmeter, and access to a manufacturer’s wiring schematic will be necessary to successfully diagnose this code
Begin your diagnosis with a visual inspection of all wiring and connectors
- Repair or replace damaged, disconnected, shorted, or corroded wiring, connectors, and components as necessary
- Always retest the system after repairs are completed to ensure success.
If all system wiring, connectors, and components (Including fuses) appear to be in normal working order, connect the scanner (or code reader) to the diagnostic connector and record all stored codes and freeze frame data
- This information can be extremely helpful in diagnosing intermittent conditions that may have contributed to this code being stored
- After the codes are cleared, operate the vehicle to see if the code returns
- If the code fails to immediately return, you may have an intermittent condition
- Intermittent conditions can prove to be quite a challenge to diagnose and in extreme cases may have to be allowed to worsen before a correct diagnosis can be made.
Continue by unplugging the electrical connector from the gear shift actuator temperature sensor and testing for reference voltage
- This is usually 5-volts but consult your manufacturer’s service manual to be sure
- If there is a 5-volt signal present with the ignition turned to the run position; check the sensor ground wire
- If both the reference signal and the ground signal are present, test the sensor resistance using the manufacturer’s temperature to resistance chart
- Compare your findings to the manufacturer’s specifications and replace the sensor if it fails to comply.
If the sensor and voltage at the sensor are within acceptable specifications, disconnect the PCM electrical connector and test circuit continuity and resistance between the sensor and the PCM
- Repair or replace system circuitry and components as required and retest the system.
Should all system circuitry and sensors check out, suspect a faulty PCM but keep in mind that PCM failure is rare and PCM replacement will require reprogramming.