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DTC codes / Chrysler codes / P1285

P1285 · ChryslerFuel Injection Pump Controller Always On

P1285 on a Chrysler vehicle means the fuel injection pump controller (a module that manages the high-pressure diesel injection pump on Cummins-equipped Rams and some other Chrysler diesels) is being commanded on when the engine computer expects it to be off, or the controller's internal circuit remains powered after the key is switched off. The powertrain control module (PCM) detects this by monitoring the controller's power feed or communication line and seeing voltage or activity where none should exist.

SystemPowertrain
Code typeChrysler specific
SeverityMedium
Fix difficultyIntermediate
AreaFuel and air metering (injector circuits)

Symptoms you may notice

  • Often no symptoms besides the warning light, especially if the controller still functions normally while running.
  • Extended cranking or a no-start condition after the engine is shut off and restarted, because the controller stays powered and drains the battery.
  • A dead battery after the vehicle sits overnight, with no other obvious cause.
  • Rough idle or intermittent misfire if the controller is stuck on and over-fuels the engine at low load.
  • A faint buzzing or clicking from the injection pump area with the key off, indicating the controller is still active.
  • Possible limp mode or reduced power if the PCM sets the code alongside other injection pump faults.

Common causes, most likely first

  1. A stuck or failed fuel injection pump controller relay that keeps the controller powered after key-off.
  2. A short to battery voltage in the controller's power feed or signal wire, often from chafed harness insulation near the pump or firewall.
  3. Internal failure in the fuel injection pump controller itself, causing it to remain active regardless of the PCM command.
  4. A faulty ignition switch or key-off power circuit that continues feeding the controller when it should not.
  5. Corrosion or water intrusion in the controller connector, creating a conductive path between power and signal pins.
  6. A PCM software or internal driver fault that fails to command the controller off, though this is less common than wiring issues.

How to diagnose and fix it

  1. Verify the battery is fully charged and perform a parasitic draw test with the key off to confirm the controller circuit is staying powered.
  2. Inspect the fuel injection pump controller relay and swap it with an identical known-good relay to see if the code returns.
  3. Disconnect the controller connector and check for battery voltage on the power feed with the key off; if present, trace the circuit back to the relay and ignition switch.
  4. Perform a wiggle test on the harness between the controller, relay, and PCM while monitoring the code or voltage to find intermittent shorts.
  5. Check the controller connector pins for corrosion, water intrusion, or pushed-out terminals, and clean or repair as needed.
  6. If wiring and relay are good, test the controller's internal switching with a bidirectional scan tool or substitute a known-good controller to confirm internal failure.
  7. After repairs, clear the code and drive the vehicle through a complete key-off and restart cycle to verify the controller powers down correctly.

Why the pump controller stays powered

  • A common miss is blaming the injection pump itself when the real fault is a $20 relay that sticks closed and keeps the controller alive after key-off.
  • The code can set intermittently from a chafed wire that only shorts when the engine bay is hot or the harness is wet, so a cold static test may pass.
  • Some technicians replace the controller only to find the PCM driver is the actual culprit, so always verify the PCM's command signal with a scope before condemning the controller.
  • A weak or failing battery can cause the controller to behave erratically and set P1285, so load-test the battery before diving into circuit diagnostics.
  • This code is often stored alongside communication or injector circuit codes, and fixing the power feed short may clear several codes at once.

Can I keep driving with P1285?

You can usually drive the vehicle short distances to a repair shop, but avoid leaving it parked for long periods because the controller may drain the battery and leave you stranded. If you notice a dead battery or extended cranking, stop driving and have the circuit diagnosed promptly.

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 Chrysler vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

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