3126E Truck Engines Caterpillar

Diagnostic Flash Code Retrieval


3126E HEP

"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 flash codes if the engine is equipped with a "DIAGNOSTIC" lamp:

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

  1. 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 flash code. After a two second pause, the second sequence of flashes will identify the second digit of the flash code.

Any additional flash codes will follow after a pause. These codes will be displayed in the same manner. Flash Code 55 indicates that No Detected Faults have occurred since the ignition key switch has been turned to the ON position.

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

Table 1 lists the flash codes and the table also gives a brief description of the flash codes.

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

Some codes record events. Also, some codes may also indicate that a mechanical system needs attention. Troubleshooting is not required for codes "35", "41", "47" and "55". Code 01 will not display a flash code. 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.

Table 1
    Flash Codes for 3126E Truck Engines    
Diagnostic Flash Code     Effect On Engine Performance (1)     Suggested Operator Action    
Engine Misfire Low Power     Reduced Engine Speed     Engine Shutdown     Shut Down the Engine (2)     Service (3)     Schedule Service. (4)    
12     Coolant Level Sensor Circuit Fault (5) (6)                             X    
15     An Injection Actuation Pressure Sensor Circuit Fault         X     X             X        
17     Injection Actuation Pressure Sensor Out of Range     X     X         X         X        
18     Driver Fault for the Injection Actuation Pressure Control Valve     X             X         X        
21     Sensor Supply Voltage Fault (7)         X                     X    
24     Oil Pressure Sensor fault (6)         X                 X        
25     An Inlet Air Pressure Sensor Circuit Fault         X                     X    
26     Atmospheric Pressure Sensor Fault (6) (7)                             X    
27     A Coolant Temperature Sensor Fault (5) (7)                             X    
28     Check Throttle Sensor Adjustment.                             X    
29     Check PTO Throttle Sensor Adjustment (6)                             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     An Inlet Air Temperature Sensor Fault (7)     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    
44     Fuel Level Sensor Circuit Fault (6)                             X    
46     Very Low Oil Pressure (6)                 X     X     X        
47     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 Parameters or System Parameters.         X     X                 X    
58     A 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        
64     Very High Intake Manifold Air Temperature Warning         X     X     X         X        
71     Ignition Key Switch Circuit Fault     X     X         X         X        
72     Cylinder 1 Fault or Cylinder 2 Fault     X     X                 X        
73     Cylinder 3 Fault or Cylinder 4 Fault     X     X                 X        
74     Cylinder 5 Fault or Cylinder 6 Fault     X     X                 X        
( 1 ) An "X" indicates that the effect on engine performance may occur if the code is active.
( 2 ) Shut Down the Engine: Operate the engine cautiously. Get immediate service. Severe engine damage may result.
( 3 ) The operator should go to the nearest location that has a qualified service program.
( 4 ) Schedule Service: The problem should be investigated when the operator has access to a qualified service program.
( 5 ) These Flash Codes reduce the effectiveness of the Engine Monitoring feature when the codes are active.
( 6 ) The code will flash if the sensor is used for this application.
( 7 ) These Flash Codes may affect the system under specific environmental conditions such as engine start-up at cold temperature and cold weather operation at high altitudes.

For further information or assistance for repairs, consult an authorized Caterpillar dealer.

Back to top
The names Caterpillar, John Deere, JD, JCB, Hyundai or any other original equipment manufacturers are registered trademarks of the respective original equipment manufacturers. All names, descriptions, numbers and symbols are used for reference purposes only.
CH-Part.com is in no way associated with any of the manufacturers we have listed. All manufacturer's names and descriptions are for reference only.