P0230 OBD2 Code Diagnosis: Fuel Pump Relay No Power in 2010 Buick Lucerne 3.9L

The P0230 code indicates a problem with the fuel pump control circuit—specifically, the signal from the PCM to the fuel pump relay. Before replacing any components, verify that the control wire (circuit 465) is not open, shorted to power, or grounded. Also check if the fuel pump fuse receives power under key-on and crank conditions. Look for other related codes such as B-codes or security light issues. An aftermarket alarm or remote starter could interfere—though you've already disconnected it. I’ll review a wiring diagram when available and provide further advice.

No additional diagnostic codes are present. The aftermarket remote starter was fully disconnected, and the issue persists. I initially thought the PCM might be faulty because I read that it supplies power to the fuel pump circuit—but I'm still unsure of its exact location in the vehicle.

To test the fuel pump relay: remove the relay and use a test light connected to battery negative. With the key on, terminal 30 should show constant 12V (B+). During engine cranking, terminal 86 should illuminate—also for about two seconds when the key is turned from off to on. If these tests pass, consider replacing the relay. However, if no power is detected at any terminals, the issue may lie in the control circuit or PCM.

I replaced the fuel pump relay with no improvement in symptoms.

The control circuit must be tested—replacing parts without diagnosing is not recommended. The absence of power at the fuel pump fuse suggests deeper issues. Probe terminal 85 on the relay (control side) with a test light when key-on and during crank position. For the 2010 Buick Lucerne, circuit 465 (dark green/white wire) should carry 12V from the PCM to terminal 85 of the relay—only briefly when commanded. This signal is critical for fuel pump activation.

Correction: Terminal 86, not 85, receives power from the PCM on the control side. The load side (terminal 30) has constant power; terminal 85 is grounded via chassis ground (terminal 301).

I tested all relay terminals with a test light, turning the key on and off repeatedly—no illumination at any point.

Did you verify that your test light works properly? Connect the positive terminal of the battery directly to the test light’s probe to confirm functionality. Then, with the relay removed, touch each cavity one by one—did no lights appear during key-on or crank position? This is essential for diagnosing a dead control circuit.

Relays have two sides: load side (power) and control side (signal). If there's no power at terminal 30, and no signal on the control wire (465), you likely have two separate issues—one in the power feed to the relay and one in the PCM-to-relay control circuit.

The test light was confirmed functional before and after testing. What should I check next? Is the dark green/white wire (circuit 465) from the PCM present on my 2010 Buick Lucerne? And is fuse 1340 (orange, underhood) always hot—should it be powered continuously?

If there's no signal from the PCM, inspect the wiring harness between the PCM and relay. Check for opens or grounds in circuit 465 (dark green/white). The engine cranks normally—yes. I do see fuse 1340 (orange) is hot at all times. However, without a proper wiring diagram, troubleshooting remains difficult. A detailed schematic specific to the 2010 Buick Lucerne would be invaluable here.

I’ve heard that the back-seat fuse box (often called the secondary fuse panel) can have connection issues—even if it appears clean. A faulty contact or corroded terminal could prevent power from reaching the relay. In some cases, replacing the entire fuse box resolves the issue. However, Buick-specific diagrams are hard to find and not widely available online.

I'm now testing the wire from the PCM (circuit 465). The engine cranks normally. The back-seat fuse box appears new with no visible corrosion or dirt—minimal use of that area makes it unlikely to be the root cause.

My tests show zero voltage at both the fuel pump relay and fuel pump fuse (no power even momentarily). I’ve concluded the issue lies within the PCM. The GM Parts Direct site lists the Powertrain Control Module as including ignition module, ECM, and wiring harness—so which component is responsible for the fuel pump permissive signal? Can anyone point me to a reliable wiring diagram showing where circuit 465 originates from in the PCM?

I’ll share the wiring diagram soon. I’ve asked a colleague to locate one—let’s see if it becomes available. Note: ECM and BCM modules require reprogramming after replacement—they are not simply plug-and-play units.

I now have access to the wiring diagram. In the 2010 Buick Lucerne, the PCM supplies 12V via a dark green/white wire (circuit 465) to terminal 85 of the fuel pump relay when commanded—this signal is active during key-on or crank position. Terminal 30 on the relay receives constant 12V (always hot). The load side has fuse 1340, which only powers when the relay closes. Key findings: 1) No 12V at terminal 30 of the relay—this is critical. 2) No signal (12V) on circuit 465 from PCM to relay terminal 85. To verify: Check terminal 6 on the PCM for circuit 465 (dark green/white). Test for continuity, grounding, or short to voltage. The PCM monitors this circuit and will set P0230 if signal is absent or incorrect.