When a vehicle’s “check engine” light comes on, it means that the Onboard Diagnostic System (OBD II) has detected a malfunction that may cause emissions to exceed the maximum allowable by law. The OBD II sends one or more trouble codes to the vehicle. A code reader is connected to an adapter beneath the vehicle’s dash to retrieve the code. Codes indicating transmission problems fall under the category of Powertrain or “P” codes.
Global and Manufacturing Error Codes
There are two types of codes: Global and Manufacturer Specific. Global codes have a “0” as the second character and are common to all vehicles. Manufacturer Specific codes are characterized by a “1” as the second character and are used for certain makes and models. For example, codes between P1700 and P1999 are Ford powertrain fault codes and P1700 to P1899 are for General Motors. Below are the most common global trouble codes for transmission problems.
Most Common Global Trouble Codes for Transmission Problems
- P0218: Transmission Over Temperature
This code usually means the transmission is overheating. This can occur if the transmission fluid is low, the lines are restricted or the cooling fan is not operating. It may also indicate that the fluid sensor needs to be replaced. In combination with other codes, the transmission may require more extensive diagnostics to determine the cause. The code may be displayed in all transmission types.
- P0613: Transmission Control Module (TCM)
A poor electrical connection or shorted TCM harness can cause this code to be generated. There could also be a programming error in the transmission control module. The latter will require replacement of the TCM. The P0613 code is specific to automatic transmissions.
- P0614: ECM/TCM Incompatible
The TCM and ECM (Engine Control Unit) are not communicating. This code usually occurs when either the TCM or ECM has been replaced, and the replacement part is not configured to work with the existing part. These parts are designed to operate with only one specific automobile and are not reprogrammable. The code is applicable to automatic transmissions.
- P0700: Transmission Control System Malfunction
The TCM is responsible for relaying fault codes that turn on the vehicle’s “check engine” light. The P0700 code indicates that there is a problem with the TCM which prevents it from turning on the light. This code is produced by vehicles with an automatic transmission.
- P0706: Transmission Range Sensor Circuit Range/Performance
The transmission range sensor conveys information about the gear the vehicle is in to the TCM and powertrain control module (PCM). The code may result from defective or corroded manual shift valve linkage, dirty transmission fluid or a defective transmission range sensor. The P0706 code is displayed for vehicles with an automatic transmission.
- P0715: Input/Turbine Speed Sensor Circuit Malfunction
The transmission’s input speed sensor signals the TCM to enable it to shift the transmission to the proper gear needed for changes in speed. If the TCM is receiving an erratic signal, the P0715 code will be produced. This may be the result of a faulty valve body, engine coolant temperature sensor, shift solenoids or input/turbine speed sensor. This code is specific to vehicles with an automatic transmission.
- P0720: Output Speed Sensor Circuit Malfunction
This code is generated when the PCM does not receive an adequate signal from the output speed sensor circuit or if there is an abnormal RPM difference between the input RPM sensor and the output speed RPM sensor. It usually indicates that the transmission is slipping. This may be caused by dirty transmission fluid, a faulty engine coolant temperature sensor or defective output speed sensor. The P0720 code is displayed for automatic transmissions.
Trouble codes between P0729 and P0736 indicate problems with the gear ratio. Each code specifies the individual gear. These codes may occur if the transmission fluid is low, a clutch in the torque converter malfunctions or if there is a damaged solenoid. All of the above codes are produced by vehicles with an automatic transmission.
Solenoid failure can prevent the flow of transmission fluid into the transmission’s hydraulics and cause a gear not to shift properly. If this occurs, a code between P0750 and P0770 will be produced, depending on the gear affected. These codes are produced in automobiles with an automatic transmission.