baileys diesel injectors

Euro 5 Hilux / Prado Injectors: Fault Code P1601

600 300 Brooke Hamilton

600x300 G Scan

When fitting injectors to the newer Hilux / Prado models (part number 295050-0460), you may see a fault code of P1601 after coding the injectors to the ECU.

The Baileys R & D team have determined that this is due to these vehicle models having a function called Pilot Quantity Learning, where the ECU can self-learn (forced) the pilot injection quantities, and stores this data in conjunction with the code.

This error arises because you’ve now changed the code, the ECU knows that post-factory injectors have been installed, and is detecting a conflict in the stored ‘learned’ values.

We have the Solution

The process when changing these injectors is:

  1. Change Injectors
  2. When ready to start the vehicle, input the new injectors correction codes
  3. Start the vehicle, allow to idle until max. engine temperature is reached
  4. Using your scan tool, go to the Pilot Learning function (often found under the ‘special functions’ menu) and select RUN. When the ECU is in Pilot Learn Mode, the glow plug light on the dashboard will start flashing.


  1. At this point, you need to use the foot throttle to increase engine speed past 3000rpm (no load) and let off throttle. When the engine is in deceleration, you’ll hear ‘tick tick tick’. This is the ECU actuating an injector and watching the change in Deceleration via the speed pickup on the flywheel.
  2. Usually you’ll cycle through (rev up and let fall) around 30 times, but we’ve had some take over 100 cycles.
  1. Once completed, the P1601 fault code can now be deleted.


Interesting Fact:

The Pilot Learning function can in effect ‘recode’ the injector in-situ, and it’s our recommendation that this is completed every 40,000kms and a standard part of the servicing checklist for your vehicle.


Guide for your Diesel Automotive Technician: If you need to print off a copy of this article for your mechanic, here is the PDF version of this article. Euro 5 Coding Tip




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