Fix P0090: Mechanic’s solutions that WORKED

The code P0090: Fuel Pressure Regulator 1 Control Circuit/Open indicates an issue with the first fuel pressure regulator’s control circuit, which can be due to a range of problems in the fuel system. This code is triggered when the vehicle’s control module detects an open circuit or an abnormal reading in the fuel pressure regulator’s control system. It’s a critical aspect of vehicle operation, as it directly influences the fuel delivery to the engine.

P0090 quick overview

Meaning	P0090: Fuel Pressure Regulator 1 Control Circuit/Open
Is it serious?	This code can be serious as it affects the vehicle’s fuel system, potentially leading to stalling or poor engine performance.
Possible causes	– Faulty fuel pressure regulator – Damaged or corroded wiring and connectors – Issues with the fuel pump or fuel pump control module – Clogged or dirty fuel filters – Air leaks in the fuel system
How to diagnose?	Inspect Fuel Pressure Regulator: Check for signs of damage or malfunction in the fuel pressure regulator. Examine Wiring and Connectors: Look for damaged, corroded, or loose wiring and connectors related to the fuel system. Check Fuel Pump and Module: Evaluate the condition and operation of the fuel pump and its control module. Assess Fuel Filters: Inspect fuel filters for blockages or dirt that could impede fuel flow. Search for Air Leaks: Investigate the fuel system for any air leaks that might cause disruptions in fuel pressure.

How to fix P0090 – learn from mechanics

I looked into P0090 service cases at iatn.com website where in the private forums the mechanics seek advice from other mechanics. I looked up a bunch of cases to help you decide how to fix your issue and see what would a real mechanic do to solve it.

Case #1: Chevrolet

Vehicle Information: 2010 Chevrolet Equinox LT 2.4L – Reduced power mode

Issue + Repair History:

• Vehicle initially had a rigged high-pressure fuel pump sitting on the head with a crooked, ineffective mount hole.
• Both Variable Valve Timing (VVT) solenoids were defective.
• After correcting these issues, the vehicle returned with a P0090 code.
• ECM (Engine Control Module) tests indicated a failure, high-pressure fuel pump regulator was out of spec, and fuel rail pressure sensor was replaced.
• Vehicle returned twice more with P0090 code. Fuel Pressure Regulator tested and found out of spec again.
• Diagnostic procedures repeatedly suggested a faulty ECM.

Other OBD2 Codes + Test Results: P0090 – Fuel Pressure Regulator Control Circuit

Suggestions to Fix Issue:

1. Suggestion to drag the connector pins at the High-Pressure Fuel Pump (HPFP) to check for intermittent connections.
2. Replace the pigtail if terminal test probe is unavailable.
3. Advised to put a manual pressure gauge on the system to compare with ECM readings. If mismatched and the pressure sensor is confirmed working, then the ECM might be at fault.

Final Fix: The problem was resolved by identifying a loose pigtail on the low side. On replacing the connector with a Delco part and performing a wiggle test, the previously heard high-pitched noise did not recur. The vehicle’s issue was resolved, pending further observation if it returns.

Case #2: Jeep

Vehicle Information: 2005 Jeep Liberty Sport 2.8L – MIL Lamp on, Lack of power

Issue + Repair History:

• Vehicle initially presented with codes P0090, P2294, and P0340.
• Discovery of a broken timing belt and bent valves, leading to a head job.
• Post-repair, two codes were cleared, but P0090 persisted.
• Vehicle’s engine runs, but still shows the P0090 code.

Other OBD2 Codes + Test Results: P0090 – Fuel Quantity Solenoid Circuit Open

Suggestions to Fix Issue:

1. Recommendation to locate the solenoid and check it with a test light/scanner; consider replacing or bypassing for testing purposes.
2. Suggestion to unplug the solenoid, short the two leads together to see if a solenoid shorted code appears, possibly requiring multiple key cycles for the code to set.

Final Fix: The issue was resolved by addressing a poor connection at the solenoid connector. The technician bent the terminals inward for a better connection, cleared the codes, and test drove the vehicle for over 20 miles, confirming the resolution of the problem.

Case #3: Ford

Vehicle Information: 2008 Ford F-450 Super Duty XL 6.4L – Stall issue

Issue + Repair History:

• Vehicle had an engine replacement due to a rod issue.
• Post-installation, vehicle stalls after 10-15 minutes of running, restarts after half an hour, then stalls again.
• Code P0090 keeps setting.
• Fuel pressure tests were normal, but air found in the fuel cooler when the vehicle stalls.
• Squealing noise heard from the lower front near the fuel cooling system pump before stalling.
• No leaks found; air purged from the fuel cooling system as per Mitchell’s instructions.

Other OBD2 Codes + Test Results: P0090 – Fuel Quantity Solenoid Circuit Open

Suggestions to Fix Issue:

1. Check for cracked oil tubes in the motor, bad IPC regulator, IPC sensor, or high-pressure oil pump.
2. Try removing the hose at the pump to get coolant down to it.
3. Electrical testing of the Fuel Volume Control Valve Solenoid and Fuel Pressure Control Valve Solenoid.
4. Check flow in and out of the fuel cooler.
5. Consider wiring chafing beneath the HP pump cover, which might require turbo and cab removal.
6. Install clear plastic in-line to check for air leaks.
7. Focus on electrical circuit problems for the fuel pressure control valve.

Final Fix: The issue was resolved by addressing the Fuel Volume Control Valve (FVCV), part of the high-pressure fuel pump unit. The FVCV was intermittently showing an incorrect resistance of 385,000 ohms, whereas the proper value should be between 1.5 – 15 ohms. The high-pressure fuel pump was replaced without removing the cab, involving the removal of turbos. This repair resolved the issue.

Case #4: GMC

Vehicle Information: 2003 GMC Sierra 2500 HD 6.6L – No Start Issue

Issue + Repair History:

• Vehicle cut out on the road and failed to restart, towed to the shop.
• Diagnostics showed MAF G/sec above 2.2 with the engine off but key on.
• Air filter showed completely blocked, removed it but still no restart.
• Cleaned Mass Air Flow (MAF) sensor.
• Encountered codes P0089, U1800, and another unreadable U code.

Other OBD2 Codes + Test Results:

• P0089
• P0090
• U1800
• Air filter found to be clogged, removed from system.
• Disconnected FPR (Fuel Pressure Regulator), but the vehicle still wouldn’t run.

Suggestions to Fix Issue:

1. Check for simple issues like a cracked water in fuel sensor allowing air into the system.
2. Inspect for a failed crank sensor at the transmission housing.
3. Verify if there is fuel at the filter.

Final Fix: The problem was solved by addressing the basics – air and fuel requirements for a diesel engine. The air filter was 100% blocked, starving the engine of air and causing no smoke. After pressurizing the fuel system, the vehicle ran beautifully. Additionally, the fuel filter was replaced as a precaution, having been found only hand-tight.

Case #5: Volvo

Vehicle Information: 2005 Volvo V50 T5 2.5L – Hesitation, Surge, Cuts out, MIL Lamp on

Issue + Repair History:

• Vehicle experiences misfires and cuts out at around 6000 RPM in 1st and 2nd gear.
• Feels like it runs out of fuel and briefly loses power.
• Codes retrieved: PO193 (Fuel Rail Sensor Circuit High) and PO090 (Fuel Pressure Regulator Control Circuit).
• No prior repair history as this is a new customer.

Other OBD2 Codes + Test Results:

• PO193 – Fuel Rail Pressure Sensor Circuit High
• PO090 – Fuel Pressure Regulator #1 Control Circuit

Suggestions to Fix Issue:

1. Replace the fuel rail sensor, as they are known to be failure-prone.
2. Inspect the pump electronic module, which controls the electric fuel pump, for corrosion or failure.
3. Consider potential issues with the fuel pressure sensor on the fuel rail, a glitching pump electronic module (PEM), or a failing fuel pump.
4. For intermittent problems, relocate the fuel pump control module to the trunk with an updated cable.
5. If fuel pressure is good, replace the fuel pressure sensor on the fuel rail and check harness connections for corrosion.

Final Fix: The issue was resolved by replacing the fuel pressure sensor on the fuel rail and a damaged hose from the top of the oil filter housing to the top of the valve cover. The vehicle, originally from Germany, was not registered with Volvo in the USA, so the parts had to be specially ordered after the customer registered the car with Volvo. After replacing these parts and clearing all codes, the car ran well and the customer was satisfied.

Common Advice	Description of Diagnostic Step
Check Fuel Pressure Sensor	Inspect and potentially replace the fuel pressure sensor on the fuel rail, as it can often be the source of the issue.
Inspect Fuel Pump and Related Modules	Examine the fuel pump, including the pump electronic module (PEM) and control unit, for faults or signs of corrosion.
Evaluate Electrical Connections	Thoroughly check electrical connections, especially wiring harnesses, for corrosion, chafing, or poor connections.
Confirm Air Intake and Filters	Ensure the air intake system is not clogged and the air filter is clean, as air blockage can lead to stalling or power loss.
Test or Replace Fuel Pressure Regulator	Assess the fuel pressure regulator’s functionality and consider replacing it if it shows signs of malfunction.
Address Potential Vacuum Leaks	Look for any signs of vacuum leaks that could affect the vehicle’s performance, particularly in the fuel system.