What does P0889 mean?
This diagnostic trouble code (DTC) is a generic powertrain code and applies to many OBD-II vehicles (1996 and newer). This may include, but is not limited to, vehicles from Hyundai, Kia, Smart, Jeep, Dodge, Ford, Dodge, Chrysler, etc. Although generic, the exact repair steps may vary by year, make, model, and powertrain configuration.
If your vehicle has stored a P0889 code, accompanied by a malfunction indicator light (MIL), it means the powertrain control module (PCM) has detected an out-of-range voltage or performance issue in the TCM power relay control circuit.
While some transmission control modules (for OBD-II equipped vehicles) are integrated into the PCM, most are standalone components. TCM-related codes are stored as P codes, B codes, or even U codes, depending on the vehicle’s make and model. If a P0889 code is stored, it is likely that other PCM and/or TCM codes are also stored.
The CAN is a complex wiring and connector system used to transmit data between the TCM and PCM. Data (including stored codes) can also be shared with other controllers via the CAN. Transmission input and output speed (RPM), vehicle speed, and wheel speed are all shared among multiple controllers. This data is not only used for comparison in electronic traction control systems but also in anti-lock braking systems and electronic stability control systems. This code is unique in that it is typically only stored if other traction control system-related codes are present. These may be codes related to mechanical or electronic issues.
The electronic transmission control systems of OBD-II equipped vehicles are managed using a network of computers (called control modules). This involves constant communication between different control modules via the controller area network (CAN).
The PCM uses input signals from multiple engine and transmission sensors to calculate the automatic shift strategy. A high-pressure pump (inside the transmission) forces fluid through the valve body and into the cam assembly; in addition to lubricating and cooling the transmission. The high-pressure fluid allows clutches to momentarily disengage from the sprag so the gear ratio can be smoothly changed. One or more electronic pressure control (EPC) solenoids help regulate fluid pressure. Electronic pressure (EP) sensors provide the PCM with relevant data regarding fluid pressure at different points in the transmission. Electronic shift solenoids are used to interrupt the flow of high-pressure fluid so the transmission shifts when commanded. The PCM uses voltage input signals from the transmission input speed sensor and transmission output speed sensor to determine if the transmission is shifting effectively.
As with many other automatic transmission malfunctions, a transmission control system code can be caused by an electrical or mechanical failure. If the PCM detects a malfunction that requires the MIL to illuminate, a P0889 code will be stored, and the MIL may light up.
How severe is this DTC?
Battery voltage is supplied to the TCM using one (or more) fuses and/or ignition relays. If the TCM or PCM detects insufficient voltage on the input supply (from the relay or fuse), a P0889 will be stored, and the MIL will illuminate.
If this code is stored, you may have noticed your transmission shifting much harder than normal. If your vehicle has displayed a P0865 code, it should be diagnosed as soon as possible.
What are some of the symptoms of the code?
Symptoms of a P0889 trouble code may include:
- Electronic traction control disabled
- Irregular transmission shifting patterns
- Transmission failure to shift
- Other associated codes
- ABS disabled
What are some common causes of the code?
Causes
of this code may include:
- Faulty relay or blown fuse (fuse link)
- Vehicle speed sensor failure
- Open or shorted circuits in the CAN
- Mechanical transmission failure
- Defective TCM, PCM, or programming error
What are the troubleshooting steps for P0889?
You will need a diagnostic scanner, a digital volt/ohmmeter (DVOM), and a reliable source of vehicle information to accurately diagnose a P0889 code. An oscilloscope can also be very useful for diagnosing various speed sensors.
You can save time by looking for technical service bulletins (TSBs) that match the stored code, the vehicle (year, make, model, and engine), and the symptoms presented. This information can be found in your vehicle information source. If you find the right TSB, it might provide a quick solution to your diagnosis.
After connecting the scanner to the vehicle’s diagnostic port and retrieving all stored codes and relevant freeze frame data, note the information (in case the code turns out to be intermittent). After that, clear the codes and test-drive the vehicle until one of two things happens; the code is restored or the PCM enters readiness mode.
The code may be more difficult to diagnose if the PCM enters readiness mode at this point, as the code is intermittent. The condition that caused the P0889 to be stored may need to worsen before an accurate diagnosis can be made. If the code is restored, proceed with the diagnosis.
You can obtain connector face views, connector pinout charts, component location diagrams, wiring diagrams, and diagnostic flowcharts (related to the code and the vehicle in question) using your vehicle information source.
Perform a visual inspection of the associated wiring and connectors. Repair or replace any wiring that is cut, burned, or damaged.
Use the DVOM to test the voltage and ground circuits at the TCM and/or PCM. If no voltage is detected, check the system relay and associated fuses. Replace faulty relays and/or blown (or otherwise defective) fuses as needed.
If voltage and ground are detected at the TCM, test the corresponding circuit at the PCM connector. If no voltage is detected there, suspect an open circuit between the component in question and the PCM. If voltage is found there, suspect a faulty TCM, PCM, or a programming error.
P0889 is typically stored due to a faulty ignition relay, a blown fuse link, or a blown fuse
