Weak or failing vehicle battery, especially under load; Corroded, loose, or damaged battery cables and ground connections; Blown fuse or faulty relay in the fuel injection pump power circuit; Chafed or shorted wiring between the ECM and the injection pump; Failing fuel injection pump actuator or internal pump electronics; Faulty ECM power supply or ground circuit (less common)

DTC codes / GM codes / P1284

P1284 · GMFuel Injection Pump Battery Voltage Out Of Range

Q: What does code P1284 mean?

Fuel Injection Pump Battery Voltage Out Of Range. P1284 on GM vehicles means the engine control module (ECM) has detected that the battery voltage supplied to the fuel injection pump circuit is outside the expected operating range. The ECM monitors this voltage to ensure the pump's electronic actuator receives stable power, and it sets the code when the signal falls too low or spikes too high.

P1284 on GM vehicles means the engine control module (ECM) has detected that the battery voltage supplied to the fuel injection pump circuit is outside the expected operating range. The ECM monitors this voltage to ensure the pump's electronic actuator receives stable power, and it sets the code when the signal falls too low or spikes too high.

SystemPowertrain

Code typeGM specific

SeverityMedium

Fix difficultyIntermediate

AreaFuel and air metering (injector circuits)

Symptoms you may notice

Illuminated check engine light, often with no other noticeable symptoms
Engine may crank but fail to start or stall shortly after starting
Rough idle or misfire under load due to inconsistent fuel delivery
Reduced engine power or limp mode in some GM models
Intermittent hesitation or stumble during acceleration

Common causes, most likely first

Weak or failing vehicle battery, especially under load
Corroded, loose, or damaged battery cables and ground connections
Blown fuse or faulty relay in the fuel injection pump power circuit
Chafed or shorted wiring between the ECM and the injection pump
Failing fuel injection pump actuator or internal pump electronics
Faulty ECM power supply or ground circuit (less common)

How to diagnose and fix it

Perform a battery load test and check charging system output with a multimeter
Inspect and clean battery terminals, grounds, and the injection pump harness connectors
Check the fuse and relay that supply power to the fuel injection pump circuit
Measure voltage at the injection pump connector while cranking and running, comparing to battery voltage
Perform a voltage drop test on the power and ground sides of the circuit to locate excessive resistance
If voltage is correct at the pump, test the pump actuator resistance and compare to GM specifications
Repair or replace damaged wiring, then clear the code and verify the repair with a test drive

Voltage Drop Tests Beat Parts Swapping

A battery that passes a basic load test can still drop voltage under the high current demand of a cold start, so test it while cranking.
Corroded ground straps on the engine block often cause this code because the pump circuit shares grounds with other high-current components.
The code can set intermittently from a loose connector that only loses contact during engine vibration, so wiggle-test the harness while monitoring live data.
A failing injection pump actuator can draw excessive current and pull the supply voltage out of range, mimicking a wiring fault.
Some GM trucks store P1284 alongside glow plug or injector codes when the common power feed is compromised, so check for shared-circuit codes first.

Can I keep driving with P1284?

If the engine starts and runs normally, you can drive cautiously to a repair shop, but avoid heavy acceleration or long trips. If the engine stalls, misfires badly, or enters limp mode, stop driving and have the vehicle towed to prevent damage to the injection pump.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

Guidance is general and written for GM vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.