DTC P1605 Rough Idling

DESCRIPTION

This DTC is stored when the speed of a specific cylinder becomes low and the idle speed becomes unstable. This DTC is also stored if the vehicle runs out of fuel. Be sure to check whether there is enough fuel in the fuel tank before inspection.

P1605
DTC Detection Drive Pattern	DTC Detection Condition	Trouble Area
-	When the accelerator pedal is fully closed and the engine is idling, the speed of a specific cylinder is low for 2 to 10 seconds (1 trip detection logic).	Injector assembly Injector compensation code Fuel leak Glow system Intake air system leakage Intake air system blockage EGR system Throttle valve system Suction control valve (fuel supply pump assembly) Low quality fuel Fuel filter element sub-assembly air bleed problem Accessory problem (A/C, generator, etc.) Engine assembly ECM

Related Data List
DTC No.	Data List
P1605	Target Idle Engine Speed Engine Speed MAP MAF Coolant Temp Battery Voltage Engine Speed of Cyl #1 (to #8) Intake Air Target Common Rail Pressure Common Rail Pressure Target Pump SCV Current Injection Feedback Val #1 (to #8) Injection Volume Actual Throttle Position Actual Throttle Position #2 Target EGR Valve Pos Target EGR Valve Pos #2 Actual EGR Valve Pos Actual EGR Valve Pos #2 EGR Close Lrn. Val. EGR Close Lrn. Val #2 Glow Relay Request Glow Relay Request #2

INSPECTION PROCEDURE

In order for idling to be stable, glow system operation, fuel system operation and compression sufficient to maintain the target idling speed are necessary.

Glow system

The following malfunctions may be present in the glow system.

Engine coolant temperature sensor malfunction.

Glow plug malfunction.

Glow relay malfunction.

Fuel system

The following malfunctions may be present in the fuel system.

Fuel leakage.

Problem with injector assemblies.

Problem with fuel supply pump assembly.

Air in fuel pipe.

Engine assembly

The following malfunctions may be present in the engine assembly.

Insufficient compression.

HINT:

In contrast to normal malfunction diagnosis for components, circuits and systems, DTCs P1603 and P1605 are used to determine the malfunctioning area from the problem symptoms and freeze frame data when the user mentions problems such as engine stall.
As these DTCs can be stored as a result of certain user actions, even if these DTCs are output, if the customer makes no mention of problems, clear these DTCs without performing any troubleshooting and return the vehicle to the customer.

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

Read freeze frame data using the GTS. Freeze frame data records the engine condition when malfunctions are detected. When troubleshooting, freeze frame data can help determine if the vehicle was moving or stationary, if the engine was warmed up or not, and other data from the time the malfunction occurred.

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

1.DTC OUTPUT (RECORD STORED DTC AND FREEZE FRAME DATA (PROCEDURE 1))

Connect the GTS to the DLC3.

Turn the engine switch on (IG) and turn the GTS on.

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

Record the stored DTC and freeze frame data.

HINT:

This freeze frame data shows the actual engine conditions when the trouble occurred.

NEXT

2.CHECK FOR ANY OTHER DTCS OUTPUT (IN ADDITION TO DTC P1605)

Connect the GTS to the DLC3.

Turn the engine switch on (IG) and turn the GTS on.

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

Read the DTCs.

Result
Result	Proceed to
P1605 is output	A
P1605 and other DTCs are output	B

HINT:

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

B

GO TO DTC CHART ()

A

3.DETERMINE CAUSE OF PROBLEM (CHECK FREEZE FRAME DATA)

Determine the cause of the problem based on the freeze frame data recorded in Procedure 1.

Rough Idle #1 to #8
Judgment of Data List Values	Problem Cause	Diagnosis Note
Any of Rough Idle #1 to #8 in the freeze frame data is ON	Injector assembly	If the cylinder that displays Rough Idle ON also has a value of more than 3.0 mm³/st for Injection Feedback Val, there may be improper combustion in that cylinder. HINT: When there are temporary changes in the injection characteristics, the malfunction may not be indicated by the value for Injection Feedback Val in the freeze frame data.

Injection Feedback Val #1 (to #8)
Judgment of Data List Values	Problem Cause	Diagnosis Note
Any of Injection Feedback Val #1 to #8 in the freeze frame data is more than 3.0 mm³/st	Injector assembly	If the cylinder that displays Rough Idle ON also has a value of more than 3.0 mm³/st for Injection Feedback Val, there may be improper combustion in that cylinder.

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