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P0989 OBD-II Trouble Code: Transmission Fluid Pressure Sensor/Switch E Circuit Low

diagnostic check engine light

P0989 code definition

The P0989 trouble code notes a problem with the transmission fluid pressure sensor E circuit.

What the P0989 code means

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.

What causes the P0989 code?

Potential causes of the P0989 trouble code include:

  • Defective transmission fluid pressure sensor
  • Malfunctioning electronic pressure control solenoid
  • Defective electrical components, such as wires, connectors, and fuses
  • Insufficient transmission fluid levels
  • Dirty transmission fluid
  • Blockages within the hydraulic pressure system
  • Problems within the internal transmission
  • In rare cases, a faulty PCM or transmission control module

What are the symptoms of the P0989 code?

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.

How does a mechanic diagnose the P0989 code?

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.

Common mistakes when diagnosing the P0989 code

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.

How serious is the P0989 code?

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.

What repairs can fix the P0989 code?

Possible repairs for the P0989 trouble code are:

Additional comments for consideration regarding the P0989 code

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.

Need help with a P0989 code?

YourMechanic offers certified mobile mechanics who will come to your home or office to diagnose and repair your vehicle. Get a quote and book an appointment online or speak to a service advisor at 1-800-701-6230.

The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details
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