P0148

Code

Generic P — Powertrain

Fuel Delivery Error

Brand: Generic

Type: P — Powertrain

Views: UK: 24 EN: 42 RU: 35

AI status

Completed

ready

Completed 100%

Page language: EN

Causes

Weak or failed in-tank fuel pump
Clogged fuel filter or screen
Faulty fuel pressure regulator or return restriction
Leaking or restricted fuel lines/fittings
Faulty fuel pressure sensor (fuel rail pressure sensor)
Fuel pump relay, fuse, or wiring fault (open/short/intermittent)

Symptoms

Engine cranks but hard to start or fails to start
Loss of power, hesitation, or stalling under load or acceleration
Poor idle, surging, or misfire under high demand
Long crank times or repeated cranking
Check Engine Light (MIL) illuminated with code P0148
Fuel smell from vehicle (if leak present)

What to check

Read freeze frame data and note operating conditions when code set (fuel level, engine load, temperature, RPM).
Scan for additional codes (fuel rail, injectors, communication, PCM).
Perform visual inspection of fuel lines, connections, fuel pump wiring, fuse and relay.
Listen for fuel pump prime at key-on (audible hum from fuel tank area).
Measure fuel rail pressure with a calibrated gauge at key-on and while cranking/idle and under load.
Check fuel pump current draw (amps) to identify a weak pump or internal short/high drag.

Signal parameters

Fuel rail pressure: compare to manufacturer spec (typical port-injected systems ~30–60 psi / 200–400 kPa; direct-injection systems much higher).
Fuel pressure sensor voltage: typically ~0.5–4.5 V proportional to pressure; use spec for vehicle.
Fuel pump current draw: typically a few amps (varies by vehicle); elevated or very low draw indicates problem.
Fuel pressure response: rise time and stability when pump commanded (should reach and hold spec pressure).
Fuel trim values (short/long term): significant positive trims can indicate low fuel delivery.

Diagnostic algorithm

Retrieve and record freeze-frame data and all active/pending codes. Note fuel level and operating conditions when fault occurred.
Perform a basic visual inspection: check fuel cap condition, fuel lines, connectors at pump and rail, relay and fuse status, and inspect for obvious leaks or damage.
With a scan tool, monitor fuel rail pressure and fuel pressure sensor raw value/voltage. Compare to expected values at key‑on, cranking, idle and under simulated load (WOT or road test if safe).
If pressure is low or unstable, install a calibrated fuel pressure gauge at the fuel rail. Compare readings to spec. Observe behavior when engine is started and during revs/load.
If pump does not prime or pressure is low at key‑on, check pump power and ground: verify relay operation, fuse, and voltage at pump connector (key-on and cranking).
Measure fuel pump current draw. Low current may indicate failed/weak pump; excessive current may indicate pump binding or short.
If pump electrical supply is OK but pressure is low under load, inspect/replace fuel filter and inspect fuel inlet screen/strainer for restriction. Re-test pressure.
Test/inspect fuel pressure regulator (if applicable) and fuel return lines for restrictions or leaks. Replace regulator if out of spec.
Check fuel pressure sensor wiring for open, short to ground/power, and poor connector pins. Back-probe sensor and compare voltage to pressure gauge reading.
If pressure and sensor signals are correct but symptoms persist, inspect injectors, check for mechanical engine issues that increase fuel demand, and verify PCM control and communication. Consider smoke/leak test for external leaks.
After repairs, clear codes and perform a road test with live data to confirm stable fuel pressure and no recurrence of P0148.

Likely causes

Clogged fuel filter or restricted inlet screen
Failing/weak fuel pump (loss of flow under load)
Electrical supply problem to pump (relay, fuse, connector, wiring)
Faulty fuel pressure sensor or damaged wiring
Fuel pressure regulator stuck or leaking

Fault status

⚠️ Status

Fuel Delivery Error (P0148): fuel pressure or flow not within expected range — possible causes include weak/failed pump, clogged filter, regulator fault, leaks, sensor or wiring faults. Verify fuel pressure, pump operation, electrical supply, and component condition.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 1.0-3.0 hours