Code
P1284
PONTIAC
P — Powertrain
Fuel Injection Pump Battery Voltage Out Of Range
AI status
Completed
Completed
100%
Causes
- Weak or discharged battery
- Faulty or overcharging alternator / voltage regulator
- Corroded or loose battery terminals or ground straps
- Damaged, corroded or shorted wiring to the fuel injection pump
- Faulty fuel injection pump or its internal electronics
- Blown fuse or bad pump relay
Symptoms
- Check Engine / Service Engine Soon lamp
- Hard starting or no start
- Intermittent stalling or poor running
- Loss of driveability or reduced engine power
- Possible fuel pump inoperative or runs intermittently
What to check
- Perform visual inspection of battery, terminals, ground straps and pump connectors for corrosion, looseness or damage
- Check and record battery voltage at rest, key ON (run) and while cranking using a quality DMM
- Measure charging system voltage at idle and with increased engine speed (expect ~13.5–14.8 V)
- Scan for stored freeze frame and live data for system voltage and any related codes
- Check fuse(s) and relay for the fuel pump circuit and verify relay operation
- Backprobe the fuel injection pump power and ground pins to confirm voltage under different conditions
Signal parameters
- Battery voltage (key ON, engine off): typically 12.2–12.8 V (varies by charge state)
- Battery voltage (engine running): typically 13.5–14.8 V
- Voltage at pump power pin (key ON/run): near battery voltage (within ~0.5 V)
- Cranking voltage: should not fall below ~9–10 V for normal cranking
- Voltage drop to ground on pump circuit: should be minimal (less than ~0.5 V)
Diagnostic algorithm
- Retrieve freeze frame and freeze / pending code data with a scan tool. Note system voltage values when code set.
- Visually inspect battery, battery terminals, main grounds and harnesses to the fuel pump for looseness, corrosion, damage or rodent chewing.
- With a fully charged battery, record voltage at battery posts: key OFF, key ON (RUN), and during cranking. Compare to expected ranges.
- Start engine (if possible) and record charging system voltage at battery terminal. If outside ~13.5–14.8 V, test alternator and regulator.
- Backprobe the fuel injection pump power and ground at the connector. With key ON and engine running, confirm pump supply voltage matches battery within ~0.5 V and ground is good.
- Perform voltage drop tests: between battery positive and pump power pin, and between pump ground pin and battery negative while pump is operating or while cranking. Voltage drop should be minimal.
- Inspect and test pump relay and related fuses; swap with known good relay if available to verify operation.
- Wiggle-test wiring and connectors while monitoring voltage/live data to recreate intermittent faults.
- If wiring and power/ground are good but voltage is still out of range at the pump, bench-test or replace the pump module per manufacturer procedures.
- If pump and wiring test OK, consider PCM power/ground integrity and, if supported by diagnostics, PCM replacement or reprogramming after confirming other components.
- Clear codes and confirm repair by road test and re-scan to ensure the code does not return.
Likely causes
- Low battery voltage under load due to weak battery or poor connections
- High charging system voltage from a failing regulator
- High resistance in pump power or ground circuit (corroded connector or broken wire)
- Open/short in pump control circuit or relay
- Faulty fuel pump module that draws abnormal current
Fault status
Status
Fuel Injection Pump Battery Voltage Out Of Range — the engine control module detected the pump supply voltage outside acceptable limits. Possible causes include low/high system voltage, wiring fault, or component failure.
Repair difficulty: Medium
Diagnostic time: 1.0 - 2.5 hours
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