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Error Code P0089 is defined as Fuel Pressure Regulator 1 Performance, which refers to a problem in the fuel pressure regulator system. This happens when the PCM (powertrain control module) has detected an irregularity in its reading of the fuel pressure, which was required to maintain normal engine operation. This problem may indicate either a lean or rich condition.
Vehicles are equipped with a fuel pressure regulator to maintain a steady pressure of fuel. Some vehicles have it built in to their fuel rail assembly, while others come with a return-less fuel supply as part of their fuel pump module inside its tank.
The return-less fuel system is controlled by a computer, while both the fuel pump output and actual fuel rail pressure are determined by the fuel pressure sensor on the rail, which uses fuel temperature to read the actual pressure. When the PCM (also called as ECM or electronic control module) determines that the fuel pressure commanded is outside the set specifications, it will trigger the error code.
Note that, for vehicles with return-less fuel supply system that only uses a supply line, where fuel doesn’t go back to the tank, both commanded fuel pressure and the actual values may be checked using advanced scan tool that can read these values. If other than the P0089 there are other problems that concerns lean oxygen sensor present, then the former must be solved first.
Depending on the make and type of the vehicle, you may experience a series of drivability issues and undesirable problems. The most obvious sign is the activation of the Check Engine light on the dashboard. Other common symptoms include:
- Hard starting
- Hesitation, poor acceleration or lack of power
- Poor fuel economy lack of power
- Lean or rich conditions
In some cases, drivers may experience no start condition or extended cranking before starts.
Error Code P0089 is usually a mechanical fault which, most of the time, can be attributed to the defective electronic fuel pressure regulator or it can be a case of faulty fuel pump. Other most common causes include:
- Clogged fuel filter or pinched or restricted fuel lines
- Low fuel condition
- Faulty fuel pump
- Defective fuel rail sensor
- Damaged, open or shorted wires (corroded wires)
- Damage in electrical connectors
- Error on fuel pump output
How to Check
Qualified mechanics start their diagnosis by hooking up their advanced level scan tool to the PCM. Any error code present will have its own freeze frame data, which includes any info that tells mechanic what circumstances triggered the PCM to set the code. This includes information about the vehicle’s speed, RPM, coolant temperature, etc.
Then, the codes will be cleared and the vehicle will be taken for a test drive.
When the code returns, the mechanic will then conduct a visual inspection of the vehicle and look for signs of damage, restriction or leaks along the fuel lines and fuel pressure regulator.
If all seems well upon visual inspection, the vehicle will now be tested for test port. This is where the mechanic will check the fuel pump output using his scan tool. He will also test the operation of fuel pressure regulator.
How to Fix
The most common fixes for this error code are:
- Replace or repairing the damaged or restricted fuel lines
- Replace fuel pressure regulator
- Replace clogged filters or screens
- Replace failed fuel pump
Repair or replace any system circuitry as needed and clear codes. This includes connectors and/or components.
Test drive the vehicle to ensure you have actually corrected the trouble code.
The most common mistake most people make on this error code is that they hastily replace the fuel pressure regulator when, in fact, it is the fuel rail sensor that it defective. This is where the importance of proper diagnosis really comes into play.
For proper diagnosis, you will need a manual fuel pressure test kit for accurate testing of fuel pressure settings to be taken at the fuel rail, and professional level scan tool to get vital information such as fuel pressure, sensor data, voltage and ohms.