1994/08/30 Caterpillar

3176B (9CK);
3406E (5EK) Truck Engines

SUPPLEMENT: 09/01/94

Truck Engine News, August 1994, Page 4, "December 1993 FLASH File Update And Fan Control Logic"

In the first paragraph of the article, the second sentence is not correct. The correct second sentence follows:

A cross reference to the service replacement modules can be found in FIND FULL-TEXT, under DOC. TYPE "FLASH".

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The December 1993 FLASH files contain the following changes. A cross reference to the service replacement modules can be found in the FIND SIRS.

* Modified High/Very High Intake Manifold Temperature Diagnostic strategy to eliminate logging of diagnostic codes on new trucks during OEM dyno tests. Update the software instead of replacing the sensor.

* On 3406E Only.Modified Boost Pressure Sensor Open Circuit Diagnostic to prevent logging the diagnostic code under high load conditions. Update the software instead of replacing the sensor.

* Modified 3176B Oil Pressure Map to eliminate false logging Low/Very Low Oil Pressure (FC 100-01 and 110-11) Codes. Update the software instead of replacing the sensor.

* Eliminated ECAP from showing 1 to 3 PSI when engine is NOT running. Update the software instead of replacing the sensor.

* Modified Snapshot Recorder to properly record Snapshots with no diagnostic clock hours or engine speed.

* Modified Fan Strategy to include Inlet Manifold Temperature.

NOTE: Cooling fan will NOT latch "ON" if Inlet Manifold Air Temperature Sensor diagnostic is Active. Very early pre-production engines did latch fan "ON".

Fan Control Logic "ON"

The ECM turns the Fan "ON" if engine Speed is less than 2250 RPM AND any One of the following conditions exist:

* Engine not running

* During engine cranking

* Coolant temperature is greater than 96° C (205° F)

* Coolant temperature sensor fault is active

* Engine retarder is "ON" in the "HIGH" mode more than 10 seconds and the coolant temperature is greater than 80° C (176° F)

* A/C High pressure switch is open or ECM is counting (30 to 600 seconds-programmable)

* A/C High pressure switch fault is active (FC 228-03)

* NEW - Intake manifold air temperature more than 87° C (187° F)

* NEW - Intake manifold air temperature more than 72° C (162° F) and Boost pressure more than 70 kPa (10.2 PSI)

NOTE: The fan will remain "ON" for a minimum of 30 seconds following ECM initiated activation except following engine start up. Following engine start up, the fan driver will keep the fan on for 2 seconds after the engine has reached the programmed Low Idle (600-750 RPM)

Fan Control Logic "OFF"

The ECM turns the Fan "OFF" if engine speed is more than 2300 RPM or All of the following conditions exist:

* Coolant temperature less than 92° C (198° F)

* No active coolant temperature sensor faults

* Retarder solenoid is not operating in the "HIGH" mode or coolant temperature is less than 75° C (167° F)

* A/C high pressure switch closed and the ECM is not counting or ECM parameter programmed to 0 seconds (disabled)

* The fan has been on for at least 30 seconds

* NEW - Intake manifold air temperature is less than 66° C (151° F)

NOTE: The fan will NOT latch on if the intake manifold temperature sensor diagnostic code is active.