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)
Table 1. 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

  • Intake system (Air leaks or deposit accumulation)

  • Throttle body assembly

  • Air fuel ratio sensor

  • Heated oxygen sensor

  • Camshaft timing oil control assembly

  • Variable Valve Timing system (VVT system)

  • Brake booster assembly

Other control systems

  • ECM

  • Wire harness or connector

  • Knock sensor

  • Engine coolant temperature sensor

Engine

  • Thermostat

  • Engine assembly

  • Engine mount

High load from another system

  • Air conditioning system

  • Power steering system

  • Electrical load signal system

  • CVT system

CAUTION / NOTICE / HINT

Tip:

  • 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 (for CVT)) 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 ignition switch to ON.

    3. Turn the GTS on.

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

    5. Read the DTCs.

      Result

      Result

      Proceed to

      Only DTC P1605 is output

      A

      DTCs other than P1605 are output

      B
      Tip:

      • 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.

    GO TO DTC CHART

    (Click here)

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

    1. Connect the GTS to the DLC3.

    2. Turn the ignition switch to ON.

    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).

      Table 2. Result

      Freeze Frame Data Item for DTC P1605

      Suspected Area

      Action

      Proceed to

      • Rough Idle #1 to #4

      • Plural Cylinders Rough Idle

      Rough Idle Status

      Compression Leakage Count

      "One of Rough Idle #1 to #4 is ON"

      and

      "Plural Cylinders Rough Idle is OFF"

      "Misfire"

      0

      • Spark plug

      • Ignition coil assembly

      • Fuel injector assembly

      Go to Rough Idling (from step 8)

      A

      One of the following is displayed:

      • Continuous poor combustion

      • Intermittent poor combustion

      • Low frequency poor combustion

      0

      • Fuel injector assembly

      • Spark plug

      • Ignition coil assembly

      Plural Cylinders Rough Idle is ON

      One of the following is displayed:

      • Misfire

      • Continuous poor combustion

      • Intermittent poor combustion

      • Low frequency poor combustion

      0

      • Mass air flow meter

      • Fuel injector assembly

      • Fuel system

      • Air fuel ratio sensor

      Go to Rough Idling (from step 15)

      B

      "One of Rough Idle #1 to #4 is ON"

      or

      "Plural Cylinders Rough Idle is ON"

      One of the following is displayed:

      • Misfire

      • Continuous poor combustion

      • Intermittent poor combustion

      • Low frequency poor combustion

      1 or more

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

      Check compression and clean deposits in combustion chamber and intake system.

      C

    DETERMINE CAUSE OF MALFUNCTION FOR MULTIPLE OR ALL CYLINDERSClick here

    PERFORM ACTIVE TEST USING GTS (CHECK THE CYLINDER COMPRESSION)Click here

  3. DETERMINE CAUSE OF MALFUNCTION FOR INDIVIDUAL CYLINDER

    1. Perform troubleshooting from Rough Idling step 8 (PERFORM ACTIVE TEST USING GTS (CONTROL THE INJECTION VOLUME)) and onward.

    GO TO ROUGH IDLING

    (Click here)

  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.

    GO TO ROUGH IDLING

    (Click here)

  5. PERFORM ACTIVE TEST USING GTS (CHECK THE CYLINDER COMPRESSION)

    1. Warm up the engine.

    2. Turn the ignition switch off.

    3. Connect the GTS to the DLC3.

    4. Turn the ignition switch to ON.

    5. Turn the GTS on.

    6. Enter the following menus: Powertrain / Engine and ECT / Active Test / Check the Cylinder Compression.

      Tip:

      To display the entire Data List, press the pull down menu button next to Primary. Then select Compression.

    7. While the engine is not running, press the RIGHT or LEFT button to change Check the Cylinder Compression to ON.

      Tip:

      After performing the above procedure, Check the Cylinder Compression will start. Fuel injection for all cylinders is prohibited and each cylinder engine speed measurement enters standby mode.

    8. Crank the engine for about 10 seconds.

    9. Monitor the engine speed (Engine Speed of Cyl and Av Engine Speed of All Cyl) displayed on the GTS.

      Tip:

      At first, the GTS displays extremely high cylinder engine speed values. After approximately 10 seconds of engine cranking, each cylinder engine speed measurement will change to the actual engine speed.

      Note:

      • Do not crank the engine continuously for 20 seconds or more.

      • If it is necessary to crank the engine again after Check the Cylinder Compression has been changed to ON and the engine has been cranked once, press Exit to return to the Active Test menu screen. Then change Check the Cylinder Compression to ON and crank the engine.

      • Use a fully-charged battery.

    10. Stop cranking the engine, and then change "Check the Cylinder Compression" to OFF after the engine stops.

      Note:

      • If the Active Test is changed to OFF while the engine is being cranked, the engine will start.

      • When performing the Active Test, DTC P1604 (Startability Malfunction) may be stored.

      • After performing the Active Test, make sure to check and clear DTCs.

    11. Read the value.

      Tip:

      • If the value of Data List item "Engine Speed of Cyl" of a cylinder is higher than other cylinders, the cylinder may be malfunctioning.

      • If the value of Data List item "Engine Speed of Cyl" is high for only one cylinder, compression loss is suspected.

      Table 3. Result

      Result

      Proceed to

      There is no variation in "Engine Speed of Cyl"

      (All cylinders display approximately the same value for "Engine Speed of Cyl")

      A

      There is variation in "Engine Speed of Cyl"

      (Only one cylinder displays a value for "Engine Speed of Cyl" that differs considerably)

      B

    CLEAN OFF ANY DEPOSITS

  6. CHECK CYLINDER COMPRESSION PRESSURE

    1. Measure the cylinder compression pressure. If the compression pressure of a cylinder is low, inspect the engine assembly and repair or replace parts as necessary (Click here).

    END