Technical Description of OBD-II Trouble Code
Engagement of Multiple Gears
What does that signify?
This diagnostic trouble code (DTC) is a generic powertrain code that is applicable to many OBD-II vehicles (1996-newer). This includes vehicles from various manufacturers such as Mercedes Benz, Toyota, Kia, Mitsubishi, Jeep, Chevrolet, Dodge, etc. Although it is a generic code, the specific repair steps may vary depending on the year, make, model, and powertrain configuration of the vehicle.
If your vehicle has stored a code P0893, it means that the powertrain control module (PCM) has received a data input signal indicating that multiple gears in the automatic transmission have been engaged simultaneously.
The transmission control module (TCM) may be a separate unit, but it is commonly integrated into a single housing with the engine control module (ECM). This combined unit is known as the PCM.
The PCM uses input signals from various engine and transmission sensors to calculate the automatic transmission shift strategy. Electronic shift solenoids are employed to interrupt the flow of high-pressure fluid, allowing the transmission to shift gears. If multiple solenoids are activated at the same time, multiple gears will be engaged, making it impossible to achieve the desired gear ratio.
Similar to other automatic transmission malfunctions, multiple gear engagement can also be caused by mechanical failure. When the friction material on one or more clutch discs is compromised, the hot material can effectively “weld” multiple sprags together, resulting in multiple gear engagement. This condition is accompanied by a distinct odor of burnt friction material in the fluid.
If the PCM detects that multiple gears in the automatic transmission are engaged simultaneously, it may store a code P0893 and illuminate the malfunction indicator lamp (MIL).
What is the severity of this DTC?
A stored code P0893 indicates that either a serious electrical issue or a catastrophic mechanical failure has occurred. It is crucial to rectify the conditions that led to the storage of this code as quickly as possible.
What are some of the symptoms of the code?
The symptoms of a P0893 trouble code may include:
What are some of the common causes of the code?
The causes of this code may include:
What are some P0893 troubleshooting steps?
When diagnosing automatic transmission codes, it is important to start by ensuring that the transmission fluid is clean and at the appropriate level. If the fluid level is low, locate the source of the leak and repair it. Refill the transmission with the recommended fluid and proceed.
If the fluid is excessively dark and has a strong odor of burnt friction material, it needs to be replaced. This can be done by removing the transmission pan (and draining the torque converter) or by flushing the transmission (recommended). In either case, the filter should also be replaced. When removing the pan, be careful to preserve any debris that may have accumulated. If the pan is relatively free of debris, it can be assumed that the clutches are mechanically intact. However, if there is a significant amount of friction material in the pan (and stuck to the magnet), the transmission will require a rebuild by a qualified technician.
To diagnose a code P0893, you will need a diagnostic scanner, a digital volt/ohmmeter (DVOM), and access to vehicle-specific diagnostic information.
If possible, use your source of vehicle information to find a technical service bulletin (TSB) that matches the vehicle’s year, make, and model, as well as the stored code/s and exhibited symptoms. This can provide helpful diagnostic information.
Once the transmission is filled to the appropriate level with the recommended fluid, proceed with the first step of the diagnosis.
Step 1
Use the scanner (connected to the vehicle diagnostic connector) to retrieve all stored codes and relevant freeze frame data. It is advisable to write down this information before clearing the codes and then test-drive the vehicle until the PCM either enters readiness mode or the code is reset.
If the PCM enters readiness mode at this point, the code is intermittent and may be more challenging to diagnose. In such cases, the conditions that led to the storage of the code may need to worsen before an accurate diagnosis can be made.
Step 2
If the code is immediately reset, the next step in the diagnosis requires searching your vehicle information source for diagnostic flowcharts, connector pin-out charts, connector face views, and component testing procedures/specifications.
Step 3
Use the DVOM to test the voltage at the shift solenoids (key on and engine off). Shift solenoid circuits typically consist of a constant supply of voltage and a ground supplied by the PCM at the appropriate time to achieve the desired gear ratio.
