Transmission Control System Electrical
The PCM has detected a problem in the automatic transmission control system. A code has been stored and the service engine light illuminated. A variety of different transmission failure codes will trigger this code being stored in the PCM. Some models will also place the transmission in “limp in” mode along with this code being stored.
Code Set Parameters
In order for this code to be exhibited, the automatic transmission control system must detect an abnormal reading from one or more of its many sensors, solenoids, and/or switches. Any malfunction which causes a specific transmission component or system failure code to be stored is capable of causing this code to be stored, as well.
Symptoms can range from none at all to total transmission failure that results in a stranded motorist condition. Some of the most common symptoms may include service engine soon lamp illumination, transmission slippage, transmission overheating, harsh shifting, failure to shift (up or down), or engine stall when coming to a stop.
Common causes include torque converter clutch failure, shift solenoid failure, and transmission component slippage. By far, the most common cause of this code being stored originates from a low fluid condition. Catastrophic transmission damage (component slippage) is frequently the result of a transmission fluid leak that has remained unchecked over a long period of time. Other causes include faulty sensors, solenoids, or switches, and defective wiring harnesses and connectors.
Technicians report that many transmissions are totally rebuilt (at great cost to the vehicle owner) when component replacement can repair the problem, Many transmission shops opt to totally rebuild transmissions and replace the torque converter (especially in high-mileage vehicles) instead of repairing them. This helps them to cover themselves from additional failures during the perceived warranty period and to improve their profit margin through sheer volume of sales. Not all transmission shops practice this type of scheme.
- There are several tools which will be instrumental in attempting to successfully diagnose the conditions which contribute to this code being stored
- A suitable OBD-II scanner (or code reader) and a digital volt/ohmmeter will be most helpful in trying to perform a successful diagnosis
- Gaining access to access a manufacturer’s wiring schematic will also prove to be necessary to successfully diagnosing this code.
Perform a careful visual inspection of all PCM 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
- Continue by clearing the code and operating the vehicle to see if it returns
- This will help to determine whether or not the malfunction is intermittent.
After the codes are cleared, test drive 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 even be attempted
This type of code applies to vehicles with automatic transmissions only
- If this code is present in your vehicle that is equipped with a manual transmission, suspect a faulty PCM.
This type of code is an informational code only and does not actually isolate a particular transmission component or system failure
- When this code is stored it simply indicates that another (more specific) transmission code has been stored or a transmission problem has been detected.
While the majority of vehicles equipped with OBD-II diagnostic systems utilize a PCM, with the engine and transmission control systems integrated into one unit, some models use a separate engine control module (ECM) and transmission control module (TCM)
- When the TCM detects a fault from one of its many sensors, switches, or solenoids, it inputs a code of this type to the ECM
- Even when the engine and transmission control modules are integrated, some models use this code to activate malfunction indicator lamp illumination and initiate the transmission control limp-in mode
- In limp-in mode, electronic pressure modulation is bypassed so that maximum pump pressure can be maintained
- Maximum pump pressure is often required to allow the transmission to shift and pull
- Shifting will likely be harsh when the vehicle is in limp-in mode.
Begin your diagnosis of this code by diagnosing and repairing all other stored transmission codes
- Chances are that once the other codes are repaired, this code will not return because it is an information code.