SFI SYSTEM, Diagnostic DTC:P1605

DTC Code DTC Name
P1605 Rough Idling

DESCRIPTION

This DTC is stored if the combustion state of any cylinder is unstable.

Using the GTS, the conditions present when the DTC was stored can be confirmed by referring to the freeze frame data. Freeze frame data records engine conditions when a malfunction occurs. This information can be useful when troubleshooting.

It is necessary to check if the vehicle ran out of fuel before performing troubleshooting, as this DTC is also stored when idling is unstable due to running out of fuel.

DTC No. DTC Detection Condition
P1605

When idling with the accelerator pedal released and the vehicle stopped, this item detects when the combustion is unstable from the sudden changes in engine speed between the cylinders.

Detection for 2 to 10 seconds according to the combustion state.

(1 trip detection logic)
Trouble Area
Ignition system

  • Spark plug

  • Ignition coil assembly
Fuel system

  • Fuel injector assembly

  • Fuel pump

  • Fuel pump control circuit

  • Fuel line

  • Purge VSV system

  • Fuel quality (existence of foreign matter, degradation)
Intake and exhaust systems

  • Mass air flow meter sub-assembly

  • Intake system (Air leaks or deposit accumulation)

  • Throttle body with motor assembly

  • Air fuel ratio sensor

  • Heated oxygen sensor

  • Camshaft timing oil control valve assembly

  • Variable Valve Timing system (VVT system)

  • Brake booster assembly
Other control systems

  • ECM

  • Wire harness or connector

  • Knock control sensor

  • Engine coolant temperature sensor
Engine

  • Thermostat

  • Engine assembly
High load from another system

  • Air conditioning system

  • Power steering system

  • Electrical load signal system

  • A/T system

CAUTION / NOTICE / HINT

Tech Tips


  • DTC P1605


    • In contrast to conventional DTCs for components, circuits and systems, DTC P1605 is used to estimate the malfunctioning area from problem symptoms and freeze frame data in response to symptoms such as "rough idling", "strong engine vibrations", etc. Such problem symptoms can occur even in the following conditions:


      • Driving with long-stored fuel (fuel that has remained in the tank for long periods of time)


      • Using fuel not acclimated to the climate during a change of seasons


      • Temporarily using low-quality fuel (fuel that contains water or has poor fuel properties)


    • As DTCs may be stored when an Active Test or learning is performed, make sure to clear the DTCs before returning the vehicle to the customer.


    • If any other DTCs are output, perform troubleshooting for those DTCs first.

  • FREEZE FRAME DATA


    • Read freeze frame data using the GTS. Freeze frame data records engine conditions when a malfunction occurs. This information can be useful when troubleshooting.


    • When confirming the freeze frame data, be sure to check all 5 sets of freeze frame data Click here.


    • When confirming freeze frame data, if there are multiple items related to the cause of the malfunction, perform troubleshooting for all related items.


    • Try to operate the vehicle under the conditions recorded in the freeze frame data which were present when the malfunction occurred. Confirm the data at this time and the data when the engine is idling (engine warmed up, no load, and shift lever in D or N) and compare this data with the freeze frame data.

  • PRECAUTIONS


    • Inspections take into account the fact that the malfunction may not have recurred and place emphasis on checking the vehicle conditions present at the time when the malfunction occurred.


    • When performing inspections, jiggle the relevant wire harnesses and connectors in an attempt to reproduce malfunctions that do not always occur.

PROCEDURE


  1. CHECK ANY OTHER DTCS OUTPUT


    1. Connect the GTS to the DLC3.

    2. Turn the engine switch on (IG).

    3. Turn the GTS on.

    4. Enter the following menus: Powertrain / Engine / Trouble Codes.

    5. Read the DTCs.

      Result
      Result Proceed to
      Only DTC P1605 is output A
      DTCs other than P1605 are output B

      Tech Tips


      • If any DTCs other than P1605 are output, troubleshoot those DTCs first.

      • Using freeze frame data, confirm the conditions the moment the DTC was stored and after the DTC was stored. This information can be useful when troubleshooting.


    B

    GO TO DTC CHART Click here

    A

  2. READ FREEZE FRAME DATA (ROUGH IDLE, PLURAL CYLINDERS ROUGH IDLE, ROUGH IDLE STATUS)


    1. Connect the GTS to the DLC3.

    2. Turn the engine switch on (IG).

    3. Turn the GTS on.

    4. Using the GTS, confirm the vehicle conditions recorded in the freeze frame data which were present when the DTC was stored Click here.

      Result
      Freeze Frame Data Item for DTC P1605 Suspected Area Action Proceed to

      • Rough Idle #1 to #6

      • Plural Cylinders Rough Idle

      		 Rough Idle Status

      "One of Rough Idle #1 to #6 is ON"

      and

      "Plural Cylinders Rough Idle is OFF"

      		 "Misfire"

      • Spark plug

      • Ignition coil assembly

      • Fuel injector assembly

      • Pressure loss from valve damage, deposits jamming the valve etc.

      		 Go to Rough Idling (from step 7) A

      One of the following is displayed:


      • Continuous poor combustion

      • Intermittent poor combustion

      • Low frequency poor combustion

      • Fuel injector assembly

      • Spark plug

      • Ignition coil assembly

      • Pressure loss from valve damage, deposits jamming the valve etc.
      Plural Cylinders Rough Idle is ON

      One of the following is displayed:


      • Misfire

      • Continuous poor combustion

      • Intermittent poor combustion

      • Low frequency poor combustion

      • Mass air flow meter sub-assembly

      • Fuel injector assembly

      • Fuel system

      • Air fuel ratio sensor

      		 Go to Rough Idling (from step 15) B

    B

    DETERMINE CAUSE OF MALFUNCTION FOR MULTIPLE OR ALL CYLINDERS Click here

    A

  3. DETERMINE CAUSE OF MALFUNCTION FOR INDIVIDUAL CYLINDER


    1. Perform troubleshooting from Rough Idling step 7 (PERFORM ACTIVE TEST USING GTS (CHECK THE CYLINDER COMPRESSION)) and onward Click here.


    NEXT

    END

  4. DETERMINE CAUSE OF MALFUNCTION FOR MULTIPLE OR ALL CYLINDERS


    1. Perform troubleshooting from Rough Idling step 15 (READ VALUE USING GTS (MAF)) and onward Click here.


    NEXT

    GO TO ROUGH IDLING Click here