P0089 – Fuel pressure regulator -performance problem

By Benjamin Jerew (Contact Me)
Last Updated 2016-05-05
ASE Master Tech

Table of Contents

1. What Does Code P0089 Mean?
2. What are the common causes of code P0089 ?
3. What are the symptoms of code P0089 ?
4. How do you troubleshoot code P0089 ?
5. Codes Related to P0089
6. Get Help with P0089

What Does Code P0089 Mean?

On modern direct-injection gasoline engines and diesel engines, the high-pressure fuel pump is mounted on the engine. This mechanical pump is capable of upwards of 10,000 psi. Fuel pressure regulation is different than in low-pressure fuel injection systems, controlled electronically instead of mechanically. As the mechanical fuel pump is mounted on the cam shaft, it is constantly pumping. Depending on system design, there are a few ways to modulate fuel rail pressure.

On some return-less systems, fuel pressure is modulated by a variable-speed low-pressure supply pump controlled by the engine control module (ECM). Other return-less and fuel-return systems regulate fuel pressure using an ECM-controlled fuel pressure regulator (FPR). Some of these regulate how much fuel enters the pump itself, while others regulate how much fuel bleeds back to the tank, via the fuel-return line. The FPR may be mounted on the high-pressure fuel pump or on the fuel rail.

To modulate fuel rail pressure, the ECM commands FPR cycling, depending on demand. If more fuel pressure is required, the ECM commands a lower FPR cycle. If less pressure is required, the ECM commands a higher FPR cycle. The ECM uses the fuel rail pressure sensor to continuously monitor fuel pressure. If the ECM detects a problem, such as an unexpected increase or decrease in fuel pressure, or excessive or insufficient fuel pressure, that is, higher or lower than commanded, it will set diagnostic trouble code (DTC), DTC P0089 – “Fuel Pressure Regulator Performance,” and illuminate the malfunction indicator lamp (MIL).

This is a generic DTC description, which means that automakers may use different descriptions. Here are a few examples:

• Mitsubishi – Suction Control Valve Stuck
• Citroën – Fuel Rail Pressure Performance
• Ford – Fuel Pressure Relief Valve Open
• Chevrolet – Fuel Pressure Control Performance
  • Information Codes 00, 11, 12, 18, and 19 indicate more specific faults

What are the common causes of code P0089 ?

Depending on year, make, and model, DTC P0089 may have number of causes. Here are some of the most common.

• Air in Fuel – Because of the nature of the high-pressure fuel system, some vehicles have been susceptible to air-in-fuel failures, causing overpressure spikes or relief valve activation and internal leaks. Air can be introduced to the system if there are leaks (suction pulls in outside air), if there is a restriction in the fuel line (suction expands dissolved air into a bubble). Check for TSBs concerning this failure and resolution steps, which may require ECM reflashing or other repairs.
• FPR Failure – Like all solenoid valves, the high-pressure fuel pressure regulator can fail. The usual electrical short- and open-circuit problems apply.
• Fuel Level – If you run out of fuel, the high-pressure pump has nothing to work with, causing pressure fluctuations and possible air intrusion. Supply pump failure causes a similar situation, but do not condemn the supply pump until you have tested it, as some failure modes cut off the supply pump when there are problems detected in the high-pressure system.
• Cam Failure – Mechanical fuel pumps are driven by lobes on the camshaft. Some European vehicles have been prone to failures in this area, typically caused by infrequent or improper oil changes (wrong oil blend or viscosity). Abnormal wear results on the cam lobes or the cam follower, sometimes even damaging the pump itself. Check for TSBs regarding this condition and always use the recommended oil blend, viscosity, and interval.

What are the symptoms of code P0089 ?

Depending on vehicle type and failure mode, you may experience a number of undesirable conditions and drivability problems. You may not be able to start your vehicle at all, or it may start and run a few minutes and stall. If the engine runs, you may experience poor fuel economy, poor performance, lack of power, or rough idle. If actual fuel pressure is too high, you will likely experience engine knocking, a rich condition with possible fuel trim DTCs, even black smoke from the exhaust.

How do you troubleshoot code P0089 ?

Because of the complexity of the high-pressure fuel system, you will need a scan tool with live data-streaming capabilities for the best chance of diagnosing this problem. A high-pressure fuel pressure gauge would be helpful, but quite possibly unavailable outside of a shop environment. A DVOM (digital volt-ohm meter) will also be useful. Keep in mind that this guide will only give you some general strategies in diagnosing your problem. Specific diagnostic steps and verification data depend entirely on year, make, and model, which information can be found in a factory repair manual.

Scan Tool & Pressure Sensor Diagnostics

• Pressure Check – With your scan tool set to show ECM-commanded fuel pressure and actual fuel pressure, perhaps a couple other key items, such as engine rpm, fuel temperature, or fuel level. Check for fuel pressure readings at different times – with KOEO (Key On Engine Off), while cranking, at engine idle, or under load. Check these in comparison with expected values.
  • If fuel pressure is too high, suspect areas include: faulty fuel pressure regulator, fuel return line restriction, clogged fuel injector.
  • If fuel pressure is too low, suspect areas include: faulty fuel pressure regulator, restricted fuel filter, faulty supply pump, leaking fuel injector, worn mechanical pump or cam, or fuel leak.

Visual & DVOM Diagnostics

• Wire Harness Check – Look for any obvious problems in the wire harness, such as chafed wires, loose connectors, bent pins, backed-out pins, or corrosion. Repair as necessary and make sure all connectors are properly seated. Critical components include the ECM, Fuel Pressure Regulator, FPR Driver (if applicable), fuel injectors, fuel injector driver, and low-pressure fuel pump.
• Electrical Check –
  • Check fuses and relays for proper installation and continuity, particularly those for the ECM, fuel injector driver, and fuel pressure regulator driver (if applicable). Repair as needed.
  • With KOEO, backprobe the FPR connector, checking for power or ground, depending on the system. The FPR may be constantly powered, the ECM or FPR driver ground-cycling it, or may be constantly grounded and power-cycled by the ECM. With a DVOM, you can check for constant power or ground, but you will need a digital scope to view ECM or driver power- or ground-cycling. Lacking proper power or ground, diagnose and repair as needed.
  • Disconnect the ECM and FPR. Check for continuity between the two connectors, as well as short to ground or to each other. Repair as necessary.
  • With the FPR disconnected, measure resistance across its terminals or to ground, depending on system design. Resistance measurements across the internal coils typically range from 1 Ω to 5 Ω, and resistance to ground should be 0 Ω or ∞ Ω, depending on design. Check your repair manual for the proper specification. Replace as necessary.

Codes Related to P0089

• P0087 Fuel Rail/System Pressure – Too Low
• P0088 Fuel Rail/System Pressure – Too High
• P0090 Fuel Pressure Regulator 1 Control Circuit
• P0091 Fuel Pressure Regulator 1 Control Circuit Low
• P0092 Fuel Pressure Regulator 1 Control Circuit High

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