3126 Truck Engine (Military) Caterpillar

Diagnostic Flash Code Retrieval

Usage:

3126 1BW

"Diagnostic" Lamp

Use the "DIAGNOSTIC" Lamp or a Caterpillar electronic service tool to determine the diagnostic flash code.

Use the following procedure to retrieve the diagnostic codes if the engine is equipped with a "DIAGNOSTIC" lamp:

Turn the cruise control ON/OFF switch to the OFF position.

Move the SET/RESUME switch to either position. Hold that position until the "YELLOW" lamp begins to flash.

The "YELLOW" lamp will flash in order to indicate a two digit flash code and the SET/RESUME switch may be released. The sequence of flashes represents the system diagnostic message. Count the first sequence of flashes in order to determine the first digit of the diagnostic code. After a two second pause, the second sequence of flashes will identify the second digit of the diagnostic code.

Any additional diagnostic codes will follow after a pause. The additional diagnostic codes will be displayed in the same manner. Flash Code "55" signals that No Detected Faults have occurred since the ignition key switch was turned to ON.

For further information, assistance for repairs, or troubleshooting, refer to the Service Manual or consult an authorized Caterpillar dealer.

Table 1 lists the electronic diagnostic codes and table 1 describes the electronic diagnostic codes.

Note: Table 1 indicates the potential effect on engine performance with "ACTIVE" flash codes.

Some codes record events or some codes indicate that a mechanical system needs attention. Troubleshooting is not required for codes "35", "41", "47" and "55". Code 01 will not flash out. Some codes will limit the operation or the performance of the engine.

Table 1 indicates the potential effect on the engine performance with active flash codes. Table 1 also forms a list of Electronic diagnostic codes and descriptions.

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Table 1
	Diagnostic Flash Code or Engine Performance Relationship
Diagnostic Flash Code		Effect On Engine Performance ⁽¹⁾				Suggested Operator Action
Diagnostic Flash Code		Engine Misfire	Low Power	Reduced Engine Speed	Engine Shutdown	Shut Down the Engine ⁽²⁾	Service ⁽³⁾	Schedule Service ⁽⁴⁾
12	Coolant Level Sensor Fault ⁽⁶⁾							X
15	Injection Actuation Pressure Sensor Fault		X	X			X
17	Injection Actuation Pressure Sensor Out of Range	X	X		X		X
18	Injection Actuation Pressure Control Valve Driver Fault	X			X		X
21	Sensor Supply Voltage Fault ⁽⁵⁾		X					X
25	Inlet Air Pressure Sensor Fault		X					X
26	Atmospheric Pressure Sensor Fault ⁽⁵⁾							X
27	Coolant Temperature Sensor Fault ⁽⁵⁾, ⁽⁶⁾							X
28	Check Throttle Sensor Adjustment							X
29	Check PTO Throttle Sensor Adjustment							X
31	Loss of Vehicle Speed Signal			X				X
32	Throttle Position Sensor Fault			X			X
34	Engine RPM Signal Fault	X		X	X		X
35	Engine Overspeed Warning
36	Vehicle Speed Signal Fault			X				X
38	Inlet Air Temperature Sensor Fault ⁽⁵⁾	X						X
39	Injection Actuation Pressure System Fault		X		X		X	X
41	Vehicle Overspeed Warning						X	X
42	Check Timing Sensor Calibrations		X					X
47	Idle Shutdown Occurrence				X
49	Inlet Air Heater Circuit Fault
51	Intermittent Battery Power to ECM	X	X		X		X
55	No Detected Faults
56	Check Customer or System Parameters		X	X				X
58	Powertrain Data Link Fault							X
59	Incorrect Engine Software							X
61	High Coolant Temperature Warning		X		X		X
62	Low Coolant Level Warning		X		X		X
71	Ignition Key Switch Fault	X	X		X		X
72	Cylinder 1 or 2 Fault	X	X				X
73	Cylinder 3 or 4 Fault	X	X				X
74	Cylinder 5 or 6 Fault	X	X				X

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^( 1 )	An "X" indicates that the effect on engine performance may occur if the code is active, depending on the exact failure.
^( 2 )	Shut Down the Engine: Operate the engine cautiously. Get immediate service. Severe engine damage may result.
^( 3 )	Service: The operator should go to the nearest qualified service location.
^( 4 )	Schedule Service: The operator should have the problem investigated when convenient.
^( 5 )	These Diagnostic Flash Codes may affect the system only under specific environmental conditions, such as engine start-up at cold temperature, cold weather operation at high altitudes, etc.
^( 6 )	These Diagnostic Flash Codes reduce the effectiveness of the Engine Monitoring feature when active.