P0894 Transmission Component Slipping
OBD-II Trouble Code Technical Description
Transmission Component Slipping
What does that mean?
This diagnostic trouble code (DTC) is a generic powertrain code and applies to many OBD-II vehicles (1996-newer). That may include but is not limited to vehicles from Chevrolet, GMC, Mazda, Mercedes Benz, Toyota, Lexus, etc. Although generic, the exact repair steps may vary depending on year, make, model and powertrain configuration.
If your vehicle has stored a code P0894, it means that the powertrain control module (PCM) has received a data input signal from the input and output speed sensors which indicates that an internal transmission component is slipping.
The transmission control module (TCM) may be a stand alone unit but is most commonly integrated into a single housing with the engine control module (ECM). This is called the PCM.
The PCM utilizes input signals from multiple engine and transmission sensors to calculate automatic transmission shift strategy. Electronic shift solenoids are used to interrupt the flow of high pressure fluid so that the transmission may shift gears. The PCM uses voltage input signals from the transmission input speed sensor and transmission output speed sensor to determine if the transmission is functioning efficiently and without slippage.
As with many other automatic transmission malfunctions, a transmission slippage code may be caused by electrical or mechanical failure. Often when the friction material on one or more clutch discs is compromised, the transmission is not able to realize the desired gear ratio due to slippage. This condition is usually accompanied by the distinctive odor of burnt friction material in the fluid.
If the PCM detects a degree of transmission slippage that exceeds maximum allowable parameters, a code P0894 may be stored and a malfunction indicator lamp (MIL) illuminated.
What is the severity of this DTC?
A stored code P0894 indicates that either a serious electrical issue or a catastrophic mechanical transmission failure has occurred. Conditions which contributed to a code of this nature being stored should be rectified as quickly as possible.
What are some of the symptoms of the code?
Symptoms of a P0894 trouble code may include:
Transmission slippage Delayed and/or harsh gear engagement Erratic transmission shift patterns Strong odor of burnt friction material in transmission fluidWhat are some of the common causes of the code?
Causes for this code may include:
Catastrophic internal (mechanical) transmission failure Defective input or output speed sensor Shorted wiring for input speed/output speed sensors Faulty PCM or a programming errorWhat are some P0894 troubleshooting steps?
When diagnosing automatic transmission codes, you should begin by making sure that the transmission fluid is clean and that the transmission if filled to the appropriate level. If the fluid level is low, locate the source of the leak and repair the condition. Refill the transmission with the recommended fluid and proceed.
If the fluid is excessively dark and smells strongly of burnt friction material, it will need to be replaced. This can be accomplished by removing the transmission pan (and draining the torque converter) or flushing the transmission (recommended). Either way, you will want to replace the filter at this time too. When removing the pan from the transmission, take care to preserve whatever debris may have landed therein. If the pan is relatively clear of debris you can assume that the clutches are mechanically intact. If there is an excessive amount of friction material in the pan (and stuck to the magnet), the transmission will require a rebuild from a qualified technician.
A diagnostic scanner, a digital volt/ohmmeter (DVOM), and a source of vehicle specifi
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