Likely Causes Of An AL4 Code On The Electronic Modular Control Panel II (EMCPII) Caterpillar

Likely Causes Of An AL4 Code On The Electronic Modular Control Panel II (EMCPII)

Usage:

ENGINES3508 (5XM) WITH EUI, 3512 (6PM) WITH EUI, 3516 (7KM) WITH EUI, 3508B (4GM, 6PN, 2HW),
3521B (8RM, 6WN, 4AW),
3516B (6HN, 7RN, 1NW) GENERATOR SET ENGINES

Problem:

An AL4 code displayed on the EMCPII indicates that the engine monitoring system in the engine Electronic Control Module (ECM) has initiated a warning, derate, or shutdown. The description of the AL4 code in the EMCPII Service Manual, SENR5398 is not correct.

Instead of the description given, the text should read: "-AL4- Engine warning, derate, or shutdown active alarm. This alarm fault is displayed when the Engine Monitoring System in the engine ECM has an active warning, derate, or shutdown. Refer to Troubleshooting, 3500 EPG Engines, SENR1003."

To see the warning, derate, or shutdown event that has caused the AL4 code to appear, connect the Cat ET and go to the Logged Events screen.

There are many reasons why an AL4 code could be displayed, but two reasons are quite common. The first is that the Engine Monitoring System in the engine ECM has logged a Low Coolant Temperature event. The ECM logs a low coolant temperature event when the engine has been running for at least 10 minutes and the coolant temperature is below the programmed set point. The set point for this parameter is 63 to 85°C (145 to 185°F). Many technicians assume that a low coolant temperature warning could not occur at these high temperatures. This warning range was chosen to warn of engine over cooling problems such as a thermostat that is stuck open.

Many technicians are also confused by the fact that the EMCPII is also capable of generating a low coolant temperature warning and can illuminate the "Low Coolant Temp" warning lamp located on the Alarm Module. Although the EMCPII and the Engine Monitoring System share the same temperature sensor, they can use the sensor data independently and activate Low Coolant Temp warning at a different set point.

The set point used by the EMCPII is programmable from 0 to 36°C (32 to 97°F) by using set point P16. Refer to the EMCPII Service Manual for instructions to program this parameter. When the EMCPII detects low coolant temperature, the Low Coolant Temp light on the Alarm Module comes on. The AL4 code will not be displayed unless the Engine Monitoring System in the ECM has detected a problem. It is recommended that only one of these two systems be used to monitor the coolant temperature and that the other be disabled.

A second likely cause of an AL4 code is a high crankcase pressure event. The Engine Monitoring System in the ECM will log a high crankcase pressure event when the pressure in the crankcase has exceeded the programmed set point for a programmed length of time. As discussed in April 15, 1998, Engine TIB, "HIGH CRANKCASE PRESSURE EVENTS MAY BE LOGGED ERRONEOUSLY", erroneous high crankcase pressure events may be logged. This will cause an AL4 code to be displayed on the EMCPII panel. High crankcase pressure events may be viewed on the logged events screen on Cat ET.

Solution:

Caterpillar is investigating ways to prevent false logging of Low Coolant Temperature and High Crankcase Pressure events. This should help reduce the frequency that the AL4 code is displayed.