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P0989 is a diagnostic trouble code (DTC) for "Transmission Fluid Pressure Sensor/Switch E Circuit Low". This can happen for multiple reasons and a mechanic needs to diagnose the specific cause for this code to be triggered in your situation. Our certified mobile mechanics can come to your home or office to perform the Check Engine Light diagnostic. Once we are able to diagnose the problem, you will be provided with an upfront quote for the recommended fix and receive $20.00 off as a credit towards the repair. All our repairs are backed by our 12-month / 12,000-mile warranty.
The P0989 trouble code notes a problem with the transmission fluid pressure sensor E circuit.
The P0989 code is a generic OBD-II trouble code that detects a transmission fluid pressure sensor E circuit abnormality. In this case the “E” circuit is a region of the circuit, and not any one component. This sensor circuit is a key component of the transmission hydraulic pressure system. The powertrain control module (PCM) calculates the ideal hydraulic pressure based on performance and operations such as engine speed, vehicle speed, and throttle position, and the pressure control solenoids control this hydraulic pressure. If the PCM notes a discrepancy between the fluid pressure level and the desired level, then the P0989 code may be detected.
Potential causes of the P0989 trouble code include:
The P0989 trouble code will often be joined by the check engine soon Warning Light illuminating on the gauge cluster. It is common for there to be no other noticeable symptoms, but it’s also common for there to be serious transmission issues, such as slippage, harsh shifting, overheating, the activation of “limp-in” mode, and possibly a total inability to shift. The torque converter clutch may also be incapable of engaging or disengaging. The P0989 code is usually accompanied by a noticeable decrease in fuel efficiency.
The P0989 code will be addressed using a standard OBD-II trouble code scanner. A certified mechanic will view the freeze frame data from the scanner to assess the P0989 code, and to also look for other trouble codes that are present. In the event that numerous codes are detected, they will be addressed in the order in which they appear. The mechanic will then need to reset the trouble codes, restart the vehicle, and check to see if the P0989 code is still detected. If it is not, then an intermittent error or an inaccurate detection are likely to blame.
If the code does remain detected, then the technician will begin by checking the transmission fluid. If the fluid is dirty, it will need to be flushed from the system and replaced. If the fluid level is low, it should be replenished, and leaks should be checked for. If the fluid is highly contaminated, however, then there likely are severe problems with the transmission, and a total rebuild or replacement may be necessary.
All electrical components should then be visually inspected. Short wires, open connectors, and blown fuses will need to be replaced. Next, the mechanic can use a manual pressure gauge to check the actual hydraulic pressure relative to ideal level, as determined by the manufacturer. If the fuel pressure is low, then there is likely a malfunctioning pressure control solenoid, or a hydraulic blockage. There may also be a faulty high pressure pump or electronic pressure regulator. If the issue is still unresolved, then the ground and voltage signals from the fluid pressure sensor will need to be checked.
Following any replacements, the mechanic should pause the inspection, reset the trouble codes, restart the vehicle, and again check to see if the code remains detected. This helps identify the moment that the issue is resolved.
The most frequently made mistake when diagnosing the P0989 code comes from failing to properly adhere to the OBD-II trouble code diagnosis protocol. It is very important that mechanics abide by the protocol at all times, as this helps avoid erroneous repairs, and ensure an efficient inspection.
High pressure pumps are commonly replaced when they are in working order, because mechanics have overlooked the actual error.
In most cases, a vehicle with the P0989 trouble code will still be drivable, though there may be noticeable transmission problems. Regardless of the drivability, continuing to drive a vehicle with this code can cause irreparable damage to the transmission, so an inspection should be scheduled as soon as the code is detected.
Possible repairs for the P0989 trouble code are:
It is very common for the P0989 code to be accompanied by other codes, such as transmission slippage, shift solenoid, and torque converter clutch codes.
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