PAD AS 7G2704 - Caterpillar

System Operation Description:Use this procedure to troubleshoot the electrical system if a problem is suspected with the coolant temperature sensor or if any one of the diagnostic codes in Table 1 is active or easily repeated.
Table 1
Diagnostic Codes Table    
Code and Description    Conditions which Generate this Code    System Response    
110-3 Engine Coolant Temperature Sensor voltage above normal     The Electronic Control Module (ECM) detects a signal voltage that is more than 4.8 VDC for five seconds.     The ECM assumes the last valid value for the engine coolant temperature. The monitoring of the coolant temperature is disabled. This disables the engine protection for low coolant temperature and high coolant temperature.
The fuel is shut off. The shutdown output is activated. The code is logged.
Since the engine protection is disabled, the engine is shut down.
The alarm output is activated.    
110-4 Engine Coolant Temperature Sensor voltage below normal     The ECM detects a signal voltage that is less than 0.2 VDC for five seconds.    System OperationUse this procedure to troubleshoot any suspect problems with the engine's coolant temperature sensor. Refer to Troubleshooting, "Component Location" for graphics that show the location of the sensor on the in-line engines and on the vee engines.The sensor signal for the passive sensor is routed from the ECM to terminal 1 of the sensor connector. The sensor return for the passive sensors is routed from the ECM to terminal 2 of the sensor connector.The ECM continuously creates a pull-up voltage on the signal wire for each sensor. The ECM uses this pull-up voltage in order to detect a problem in the signal circuit. When the ECM detects voltage that is above a threshold on the signal wire, the ECM activates a high voltage -3 diagnostic code. When the ECM detects voltage that is below a threshold on the signal wire, the ECM activates a low voltage -4 diagnostic code.Note: There may be a delay of 30 seconds or more in order for Caterpillar Electronic Technician (ET) to display an active diagnostic code. When you check for a diagnostic code, be sure to wait at least 30 seconds.The following components can cause these codes:
Electrical connector or wiring
Sensor
ECMThe most likely cause of a code is a problem with an electrical connector or wiring. The least likely cause of a code is the ECM.
Illustration 1 g01431487
Schematic for the passive analog sensor
Illustration 2 g01420865
Terminal locations at the P1 ECM connector for the passive analog sensors (P1-3) Analog return (P1-27) Engine coolant temperature
Illustration 3 g01155187
Terminal locations at the connector for the passive analog sensor (Terminal 1) Sensor signal (Terminal 2) Analog sensor return
Illustration 4 g01431495
P5 terminals on bottom of terminal box for an in-line engine (P5-50) Engine coolant temperature (P5-49) Analog return
Illustration 5 g01431502
P5 terminals on bottom of terminal box for a vee engine (P5-41) Analog return (P5-42) Engine coolant temperature
Illustration 6 g01431198
Terminal Box (1) ECM connector J2/P2 (2) ECM connector J1/P1 (3) 16 amp circuit breaker (4) Connectors J3/P3 for the customer's connector (5) Connectors J4/P4 for the optional control