P2928 – Fuel Pump Secondary Circuit/Open

System: Powertrain | Standard: ISO/SAE Controlled | Fault type: Circuit/Open

Definition source: SAE J2012/J2012DA (industry standard)

DTC P2928 indicates the powertrain control system has detected an open circuit condition in the fuel pump secondary circuit. In practical terms, the module expected the fuel pump’s secondary-side electrical path to be intact and saw evidence that it was not, such as a missing electrical load or loss of continuity when the pump was commanded on. The exact monitoring strategy and which components are considered part of the “secondary circuit” can vary by vehicle, so confirm circuit routing, connector locations, and test points using the correct service information. This DTC points to an electrical circuit integrity issue, not a confirmed fuel pump mechanical failure.

What Does P2928 Mean?

P2928 – Fuel Pump Secondary Circuit/Open means the control module has identified an open (loss of continuity) in the fuel pump secondary circuit. The official definition focuses on a circuit integrity fault: the commanded operation of the fuel pump does not produce the expected electrical response because the secondary circuit appears broken, disconnected, or unable to carry current. Per SAE J2012 DTC conventions, this is an electrical “Circuit/Open” type fault, so diagnosis should prioritize locating an open, poor connection, or excessive resistance that effectively behaves like an open within the fuel pump secondary circuit path.

Quick Reference

• Subsystem: Fuel pump secondary electrical circuit (pump feed/return path and related wiring between the control device and the pump, as applicable).
• Common triggers: Unplugged connector, broken conductor, poor terminal fit, corrosion causing loss of continuity, or an open within the pump electrical path.
• Likely root-cause buckets: Wiring/connector faults, pump assembly electrical open, power/ground path interruption, control device/driver or relay path issue (varies by vehicle).
• Severity: Often high—may cause no-start, stall, or extended crank depending on when the open occurs.
• First checks: Verify fuel pump command vs operation, inspect connectors/grounds, check fuses and relay/control paths, and confirm continuity through the secondary circuit.
• Common mistakes: Replacing the fuel pump without proving an open in wiring/connectors or misidentifying the “secondary circuit” section on that specific vehicle.

Theory of Operation

The fuel pump is powered through an electrical circuit controlled by the powertrain system. Depending on vehicle design, the pump may be driven through a relay, a dedicated fuel pump control module, or a module-integrated driver. When the pump is commanded on, current should flow through the pump’s power and ground paths, and the control system may verify operation by monitoring the driver’s electrical behavior and/or circuit feedback.

P2928 sets when the module determines the secondary circuit is open—meaning the expected electrical load is missing or continuity is lost between key points in the pump circuit. Typical indicators include no current flow when commanded, an absence of expected circuit response, or a feedback signal that suggests disconnection. Because implementations vary by vehicle, use service information to identify which portion is defined as “secondary” and where it is monitored.

Symptoms

• No-start engine cranks but does not start due to lack of fuel delivery.
• Stalling engine may stall unexpectedly if the circuit opens during operation.
• Extended crank longer-than-normal cranking before starting if the circuit intermittently opens.
• Intermittent start vehicle may start sometimes and fail other times as connection opens/closes.
• Reduced power hesitation or loss of power if pump power is interrupted under load.
• MIL on malfunction indicator lamp illuminated with P2928 stored.

Common Causes

• Open circuit in the fuel pump secondary wiring harness (broken conductor inside insulation, cut wire, or rubbed-through section)
• Unplugged, loose, or partially seated connector at the fuel pump, pump module, inline connector, or harness junction
• Poor terminal fit, spread pins, backed-out terminals, or corrosion causing an effective open in the secondary circuit
• Open in the fuel pump secondary circuit ground return (ground splice, ground eyelet, or ground wire open)
• Open in the fuel pump secondary power feed between the control device and the pump (where design uses a separate secondary feed)
• Failed fuel pump motor or internal pump module connection creating an open load (electrical open in the pump circuit)
• Faulty fuel pump relay/contact path or control device output path (varies by vehicle) that results in an open to the pump
• Module connector issue at the controller that monitors/commands the pump circuit (poor pin fit, corrosion, or connector damage)

Diagnosis Steps

Tools typically needed include a scan tool capable of reading DTCs, freeze-frame data, and live data; a digital multimeter; and basic back-probing or terminal testing tools. A wiring diagram and connector pinout from service information are essential because circuit routing varies by vehicle. If available, use an approved test light or a fused jumper for load testing per service procedures.

1. Confirm P2928 is present and record freeze-frame and any related fuel or powertrain codes. Note whether the fault sets at key-on, during crank, or while driving, since that timing helps focus on the commanded pump state.
2. Review service information for the exact definition of “fuel pump secondary circuit” on the platform (varies by vehicle). Identify which module commands/monitors the circuit, the connector locations, and the relevant fuses/relays/grounds.
3. Clear codes and run a controlled key cycle and/or command the fuel pump ON with the scan tool (if supported). Observe whether P2928 resets immediately (hard open) or only under vibration/heat (possible intermittent open).
4. Perform a thorough visual inspection of the fuel pump circuit path: pump/module connector, intermediate connectors, harness routing near moving parts and heat sources, and any body/frame pass-throughs. Look for unplugged connectors, damage, chafing, pinched sections, or evidence of water intrusion.
5. Do a connector/terminal check: disconnect the relevant connectors and inspect for bent pins, backed-out terminals, corrosion, or poor pin tension. Correct any terminal fit issues using proper terminal tools; do not “tighten” pins with improvised methods that can cause damage.
6. With the circuit de-energized, perform continuity checks on the suspected secondary circuit segments using the wiring diagram. Verify there is continuity end-to-end and no unexpected opens at splices, junctions, or connector transitions. If an open is found, isolate by testing segment-by-segment between connectors.
7. Perform voltage-drop testing under load while the pump is commanded ON (or during crank if that is when the pump is energized). Check both the power side and the ground side of the fuel pump secondary circuit. Excessive drop indicates high resistance that can behave like an open under load; locate the exact point by moving the meter leads along the circuit.
8. Use a wiggle test while monitoring live data and/or the multimeter: gently manipulate the harness, connectors, and suspected splice locations with the pump commanded ON. If the pump command is present but circuit feedback changes or the fault resets, focus on the area that reproduces the issue.
9. If service information allows, perform a load test of the circuit using an approved method (for example, a specified test load or test light) to verify the circuit can carry current without opening. An open may not show on a simple continuity test but will fail under load.
10. Evaluate the fuel pump as an electrical load only after verifying the wiring and terminals. If the power and ground to the pump are confirmed good under command yet the circuit remains open or the load is electrically open, follow service procedures to test the pump/module for an internal open condition.
11. If the wiring, terminals, grounds, fuses/relays (as applicable), and pump load check out, inspect the controlling/monitoring module connectors for pin fit and corrosion and verify the module is providing/seeing the expected command/feedback per service information. Module replacement or programming should be last and only after circuit integrity is proven.

Professional tip: Treat P2928 as an “open-circuit” problem until testing proves otherwise. Continuity checks alone can miss a partially broken conductor or poor terminal tension; prioritize voltage-drop and load testing while the circuit is commanded ON, and use live-data logging during a wiggle test to capture intermittent opens that won’t appear during a quick bay inspection.

Possible Fixes & Repair Costs

Repair costs for P2928 vary widely because the underlying issue can range from a simple connector problem to wiring repair or component replacement. Total cost depends on accurate diagnosis time, parts required, access difficulty, and local labor rates.

• Repair or replace damaged wiring in the fuel pump secondary circuit (broken conductor, chafed harness, melted insulation).
• Clean, reseat, and secure affected connectors; correct poor pin fit, corrosion, or backed-out terminals.
• Restore power/ground integrity for the circuit as applicable (repair open feed, open ground path, or poor ground connection verified by testing).
• Replace a faulty relay, fuse holder, or in-line connector only if tests confirm an open or high-resistance condition at that point.
• Replace the fuel pump or fuel pump module only after confirming the circuit can deliver proper power/ground and the pump still does not operate.
• Repair or replace the fuel pump control module (if equipped) only after verifying correct inputs/outputs and confirming an internal open or failed driver.
• Repair the powertrain control module wiring/connectors, or replace the module only if all external circuit checks pass and control output is proven faulty.

Can I Still Drive With P2928?

P2928 indicates an open in the fuel pump secondary circuit, which can prevent the pump from running consistently. Driving may be unsafe because the engine can stall, fail to start, or lose power without warning. If you experience stalling, a no-start condition, reduced power, or any steering/brake assist warnings, do not drive—have the vehicle towed and diagnosed. If it currently runs normally, limit operation to moving it for service and avoid high-load or high-speed driving until the fault is confirmed and repaired.

What Happens If You Ignore P2928?

Ignoring P2928 can lead to intermittent or complete loss of fuel delivery, resulting in repeated no-starts, unpredictable stalling, and potential breakdowns. Continued operation with an unresolved open circuit may also cause heat damage at poor connections, worsen terminal fit, and increase the likelihood of additional electrical faults or fuel pump control component damage over time.

Related Codes

• P2901 – Diesel Particulate Filter Regeneration – Aborted
• P2900 – Fuel Rail System Performance
• P2941 – Airflow Sensor “C” Circuit
• P2940 – Airflow Sensor “B” Circuit Intermittent/Erratic
• P2939 – Airflow Sensor “B” Circuit High
• P2938 – Airflow Sensor “B” Circuit Low
• P2937 – Airflow Sensor “B” Circuit Range/Performance
• P2936 – Airflow Sensor “B” Circuit
• P2935 – Cylinder Deactivation System – Stuck Off (Bank 2)
• P2934 – Cylinder Deactivation System – Stuck On (Bank 2)

Key Takeaways

• P2928 is defined as Fuel Pump Secondary Circuit/Open and points to an electrical open condition, not a confirmed fuel pump failure.
• Most confirmed causes involve wiring, connectors, terminals, fuses/relay paths, or grounds in the fuel pump secondary circuit.
• Verify the fault with test-driven checks (continuity, voltage-drop, load testing, and wiggle testing) before replacing parts.
• Stalling or a no-start can occur; treat the condition as potentially safety-critical if symptoms are present.
• Repairs should target the proven failure point—especially opens and poor pin fit—to prevent repeat faults.

Vehicles Commonly Affected by P2928

• Vehicles using an electronically controlled fuel pump circuit with monitored secondary-side feedback (design varies by vehicle).
• Vehicles equipped with a dedicated fuel pump control module or integrated pump driver (where used).
• Vehicles with underbody harness routing near heat sources, sharp edges, or moving components that can lead to harness damage.
• High-mileage vehicles where connector terminal tension or pin fit can degrade over time.
• Vehicles frequently exposed to moisture, road spray, or corrosion-prone environments affecting connectors and grounds.
• Vehicles that have recently had fuel system, tank, or rear harness service where connectors may be left loose or terminals disturbed.
• Vehicles with prior collision or undercarriage damage that may have stressed wiring near the fuel tank area.
• Vehicles with aftermarket electrical modifications that share power/ground paths near the fuel pump circuit (integration quality varies).

FAQ

Does P2928 mean the fuel pump is bad?

No. P2928 indicates the control module detected an open in the fuel pump secondary circuit. A failed pump is possible, but the code most directly points to wiring, connectors, terminals, relay/fuse paths, or control circuitry that has opened or lost continuity.

What is the “secondary circuit” in this code?

“Secondary circuit” refers to the monitored portion of the fuel pump electrical path as defined by the vehicle’s design. Depending on the platform, it can be the pump power feed, the ground side, or a feedback/return path used to confirm the circuit is intact. Consult service information for the exact circuit naming and routing.

Can an intermittent connection set P2928?

Yes. A loose connector, poor pin fit, or a broken conductor that makes contact intermittently can behave like an open during vibration or temperature changes. A wiggle test combined with live-data logging and voltage-drop testing under load is a practical way to confirm this.

Will replacing the relay or fuse fix P2928?

It can, but only if testing proves the open is at the relay, fuse, fuse holder, or their terminals. Replacing these parts without confirming continuity and load capability may not resolve the root cause, especially if the true problem is a damaged harness or poor connector tension.

What should I check first if the engine cranks but won’t start?

Start by confirming whether the fuel pump operates when commanded (varies by vehicle), then verify the pump circuit has a complete power and ground path under load. Inspect connectors for incomplete seating or backed-out terminals, and verify continuity of the secondary circuit end-to-end. If the circuit tests good, then evaluate the pump/module based on service procedures.

For accurate pinpointing of the open, follow the vehicle-specific wiring diagram and connector views, then repair only what testing confirms as the failed section of the fuel pump secondary circuit.