P0090 means the engine control module detected an open circuit on fuel pressure regulator 1, the control solenoid on the high-pressure fuel pump. Its family is P0090 (circuit or open), P0091 (low), P0092 (high), and on many engines a second regulator uses P0093 through P0095. Manufacturers name the part differently: fuel metering valve, fuel volume regulator, MSV or MPROP on Bosch pumps, pressure control valve. It is the same two-wire solenoid.
Severity: moderate to high. Can you keep driving? Not far. Without control of the solenoid the pump either sends maximum fuel to the rail or none, depending on whether the valve is normally open or closed. The computer responds with reduced power, hard starting, or a no-start. On a common-rail diesel a rail pressure the module cannot regulate is an over-pressure risk, so most calibrations cut fueling hard. Drive to a shop only if the engine runs cleanly.
Which engines set P0090
Gasoline direct-injection engines with a cam-driven high-pressure pump: GM 1.4 L and 2.0 L turbos in the Cruze, Sonic, Equinox and others, Ford EcoBoost, Hyundai and Kia GDI, VW and Audi TFSI and TSI, and the Maserati V6. Common-rail diesels: GM Duramax, Ford Power Stroke, Ram Cummins, VW TDI. Any engine whose pump has a computer-controlled inlet valve can set it.
What the computer is measuring
Maserati's diagnostic sheet BOL 24-19 (May 2024) for the 2022 to 2023 Ghibli, Quattroporte and Levante V6 states the set condition plainly: P0090 is stored when the module detects a control current through the pump's MSV valve below 0.7 A for more than 500 ms. The module expects a known current when it drives the solenoid; an open winding, an open wire or a bad connector drops that current to zero. The code is electrical by definition.
General Motors' preliminary information PIP5198B (April 2016) for the 2015 Silverado and Sierra with the 6.6 L Duramax LML lists the fuel pressure regulator control circuit codes among a long set of faults, warning lamps, DEF messages and a crank-no-start, all traced to engine wiring harnesses chafing on under-hood components. That is the diesel version of the same lesson: the wire before the part.
Causes, in the order they are found
A chafed or broken wire in the harness to the pump, which on a GDI engine sits on the cylinder head near the cam cover and on a diesel sits low on the block near heat and vibration.
A connector problem at the pump: a terminal pushed back, corrosion, fuel or oil wicked in. On the Maserati V6 the procedure has the technician remove the injection harness to reach the connector, which says something about how often the connector is the answer.
An open solenoid winding. The solenoid lives on a pump that runs hot; windings do fail open. Measured, not assumed.
A blown fuse or a shared feed when several actuators on the same supply stop at once.
The module, last.
A diagnostic order
- Record the freeze frame and companion codes. P0087 or P0088 (rail pressure too low or high) beside it are consequences; other open-circuit codes beside it mean a harness or a shared feed.
- Open the pump connector and look. Fuel, oil, corrosion, loose terminals.
- Measure the solenoid across its two pins at the pump: a low, finite resistance (typically a few ohms; check the specification). Infinite is an open winding.
- Check both wires end to end with the module disconnected: continuity under an ohm, no short to ground or power. Flex the harness while measuring.
- Check supply at the connector, key on, if the design feeds the solenoid from a relay or fuse.
- Replace the solenoid or the pump only if the winding measured open; on many pumps the valve is not sold separately. Then clear and verify rail pressure tracks the commanded value on a road test.
Never pierce insulation to probe a fuel-system wire; back-probe at the connector.
Frequently asked questions
Can I drive with a P0090 code?
Only to a shop, and only if the engine starts and runs cleanly. Without control of the pump's regulator the module cannot manage rail pressure, and most calibrations cut power or refuse to start rather than risk over-pressure.
Is P0090 the high-pressure fuel pump?
It is the regulator solenoid on the pump, and the code means its circuit is open. A chafed wire or a bad connector produces the same open as a failed winding and is more common. Measure the winding at the pump before condemning the pump.
Why does P0090 come with P0087 or P0088?
Because once the module loses control of the regulator, rail pressure goes wherever the valve's default position sends it, and the pressure monitors set their codes. Fix the circuit and those codes should not return.
How much does it cost to fix P0090?
A harness or connector repair is usually under an hour or two. The regulator valve on pumps where it is serviceable is a moderate part; on pumps where it is not, the high-pressure pump is a major part, more on a diesel. That difference is why the winding is measured first.
Related codes
- P0091 / P0092: fuel pressure regulator 1 control circuit low or high, shorts rather than an open.
- P0093 to P0095: fuel pressure regulator 2.
- P0003 / P0004: fuel volume regulator control circuit low or high, the same solenoid under a different name on some engines; see P0003.
- P0087 / P0088: fuel rail pressure too low or too high.
The code number itself tells you the family and the domain; how to read an OBD2 code number explains what each character means.