Engine Controls - Engine Ticking Noise at Idle
TSB SB05-01-S006Underhood Tick Noise at Idle
Light Duty ASCENDER 2004 Bulletin Engine 08/01/05
Light Duty ASCENDER 2003 Bulletin Engine 08/01/05
ISSUE DATE: AUGUST 2005
Affected Vehicles:
2003-2004 Isuzu Ascender (US/UT)
Service Information
Condition:
Some customers may comment on an underhood tick noise heard while the vehicle is idling. Technicians may find that the noise does not increase or decrease with changes in the engine idle RPM. The tick noise occurs in approximately one second intervals.
Possible Cause:
This condition may be caused by the electro-viscous fan clutch control function of the Powertrain Control Module (PCM) attempting to keep the fan speed between 300-600 revolutions per minute (RPM). At idle, the cooling fan speed will drag to approximately 500 RPM then oscillate between 300 and 600 RPM. When the fan speed drops below 500 RPM, the PCM will pulse the fan control solenoid. The pulsing of the solenoid is causing the tick noise.
Correction:
Reprogram the PCM. DO NOT REPLACE the engine cooling fan clutch.
Service Procedure
Verify that the cooling fan clutch is the source of the noise by using one of the following two methods:
^ Use a Tech 2 to command the cooling fan off. If the ticking noise goes away, the pulsing of the cooling fan clutch is the source of the noise.
^ The cooling fan clutch electrical connector, located on the cooling fan shroud, may be disconnected with the engine off. If the ticking noise goes away, the pulsing of the cooling fan clutch is the source of the noise. Be sure to clear any Diagnostic Trouble Codes (DTCs) that may have set while the cooling fan clutch is disconnected.
Reprogram the Powertrain Control Module (PCM) with a new service calibration released with Isuzu Diagnostic Software (IDS) Version 2 or newer.
Refer to Service Programming System (SPS) in the Service Manual. As always, make sure your TECH2 is updated with the latest software version.
Warranty Claim Information
Use the labor operation table.
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