Use this procedure to troubleshoot the electrical system if a problem is suspected with the sensors or if any one of the diagnostic codes in Table 1 is active or easily repeated.
| Diagnostic Codes Table | |||
|---|---|---|---|
| Code and Description | Flash Code | Conditions which Generate this Code | System Response |
| 100-3 Oil Pressure voltage high | 24 | The oil pressure signal is above 4.7 VDC for one second. Also, there are no sensor supply diagnostic codes. | The diagnostic code is active and logged. |
| 100-4 Oil Pressure voltage low | 24 | The oil pressure signal is less than 0.5 VDC for one second. Also, there are no sensor supply diagnostic codes. | The diagnostic code is active and logged. |
| 100-10 Oil Pressure signal rate of change | 24 | The ECM detects signal voltage that is not changing at a normal rate for thirty seconds. | The diagnostic code is active and logged. |
| 102-03 Boost Pressure voltage high | 25 | The boost pressure sensor signal is greater than 5.0 VDC for one second. Also, there are no sensor supply diagnostic codes. | The diagnostic code is active and logged. The ECM sets the boost pressure to 600 kPa (87 psi). Engine power is limited. |
| 102-04 Boost Pressure voltage low | 25 | The boost pressure sensor signal is less than 0.75 VDC for one second. Also, there are no sensor supply diagnostic codes. | The diagnostic code is active and logged. The ECM sets the boost pressure to 600 kPa (87 psi). Engine power is limited. |
| 106-03 Atmospheric Pressure voltage high | 26 | Voltage is above 4.8 VDC for one second. Also, there are no sensor supply diagnostic codes. | The diagnostic code is active and logged. The ECM will use a default value of 100 kPa (14.5 psi). This value will also be displayed on Caterpillar Electronic Technician (ET). |
| 106-04 Atmospheric Pressure voltage low | 26 | Voltage is below 0.2 VDC for one second. Also, there are no sensor supply diagnostic codes. | The diagnostic code is active and logged. The ECM will use a default value of 100 kPa (14.5 psi). This value will also be displayed on Caterpillar Electronic Technician (ET). |
| 110-03 Coolant Temperature voltage high | 27 | Voltage is above 4.7 VDC for one second. Also, there are no sensor supply diagnostic codes. | The code is logged. The value of the parameter is set to a gauge pressure of 0° F (32° C). |
| 110-04 Coolant Temperature voltage low | 27 | Voltage is below 0.3 VDC for one second. Also, there are no sensor supply diagnostic codes. | The code is logged. The value of the parameter is set to a gauge pressure of 0° F (32° C). |
| 241-00 5 Volt Open Circuit | 21 | The supply voltage is normal. The rack signal is below 0.3 VDC. The boost signal, oil pressure signal and the coolant temperature signal are below 0.5 VDC. The engine rpm is greater than 0. | The code is active and the code is logged. All sensors are set to default values. |
| 241-01 5 Volt Short Circuit | 21 | The supply voltage for the sensors is less than 3 VDC or the supply voltage is greater than 7.0 VDC. | The code is active and the code is logged. All sensors are set to default values. |
| 241-02 8 Volt Open Circuit | 21 | The supply voltage for the sensors is normal. The rack signal is equal to 5 VDC and the coolant temperature signal is less than 0.6 VDC. | The code is active and the code is logged. All sensors are set to default values. |
| 241-03 8 Volt Short Circuit | 21 | The supply voltage for all of the sensors is less than 6.4 VDC or the supply voltage is greater than 9.6 VDC. | The code is active and the code is logged. All sensors are set to default values. |
Use this procedure to troubleshoot any suspect problems with the following sensors:
- Coolant temperature sensor
- Engine oil pressure sensor
- Atmospheric pressure sensor
- Intake manifold pressure sensor
 | |
| Illustration 1 | g01652647 |
 | |
| Illustration 2 | g01657635 |
(10) + 8 VDC (20) Coolant temperature (25) Boost pressure (26) Coolant level (27) Oil pressure (30) + 5 VDC (34) Atmospheric pressure (35) Analog return (40) Rack position | |
The supply voltage is routed to terminal (A) of each sensor connector. The sensor return is routed to terminal (B) of each sensor connector. The sensor signal is routed to terminal (C) of each sensor connector. The ECM provides short circuit protection for the internal power supply. A short circuit to the battery will not damage the internal power supply.
 | |
| Illustration 3 | g01159881 |
Sensor connector (A) 5 V sensor supply (B) Sensor return (C) Signal | |
Test Step 1. Check for Active Diagnostic Codes or Logged Diagnostic Codes
- Connect Caterpillar Electronic Technician (ET) to the service tool connector.
- Turn the engine control switch to the ON position.
- Monitor the diagnostic codes on Cat ET. Check and record any diagnostic codes.
Note: Wait at least 30 seconds in order for the diagnostic codes to become active.
- Determine if a diagnostic code has occurred several times.
Note: A diagnostic code that is logged several times is an indication of an intermittent problem. Most intermittent problems are the result of a bad connection between a socket and a pin in a connector or a bad connection between a wire and a terminal. The problem may be caused by moisture, corrosion, or wear.
- Determine if the problem is active and related to one of the following diagnostic codes:
- 03
- 04
- 03
Expected Result:
A diagnostic code is not active.
Results:
- OK - A diagnostic code is not active.
Repair: The problem may be intermittent. If the problem is intermittent, refer to Troubleshooting, "Electrical Connectors - Inspect".
STOP
- Not OK - A 04 diagnostic code is active. Proceed to Test Step 2.
Test Step 2. Disconnect the Sensor and Check for an Open Circuit Diagnostic Code
- Disconnect the suspect sensor.
- View active diagnostic codes on CAT ET.
Note: Wait at least 30 seconds in order for the diagnostic codes to become active.
Expected Result:
An active diagnostic code (03) appears for the disconnected sensor.
Results:
- OK - An active diagnostic code (03) appears for the disconnected sensor.
Repair: There is a short in the sensor or the connector. Repair the connector. If the problem still exists, replace the sensor.
STOP
- NOT OK - An active diagnostic code (03) does not appear for the disconnected sensor. Proceed to Test Step 3.
Test Step 3. Create a Short at the Sensor Connector
- Turn the engine control switch to the OFF position.
- Disconnect the suspect sensor.
- Use a wire jumper in order to create a short between terminal (C) and terminal (B) at the sensor connector.
- Turn the engine control switch to the ON position.
- Monitor the diagnostic codes on Cat ET. Check for an active 04 diagnostic code for the suspect sensor.
Note: Wait at least 30 seconds in order for the diagnostic codes to become active.
- Turn the engine control switch to the OFF position.
Expected Result:
A 04 diagnostic code is now active for the suspect sensor(s).
Results:
- OK - A 03 diagnostic code was active before creating the short at the sensor connector. A 04 diagnostic code became active after creating the short at the sensor connector. The harness and the ECM are OK. There may be a problem with the sensor.
Repair: Temporarily connect a new sensor to the harness, but do not install the new sensor in the engine. Verify that there are no active diagnostic codes for the sensor. If there are no active diagnostic codes for the sensor, permanently install the new sensor. Clear any logged diagnostic codes.
STOP
- Not OK - A 03 diagnostic code is still active for the suspect sensor(s). The problem may be in the harness or with the ECM. Proceed to Test Step 4.
Test Step 4. Test the Operation of the ECM
- Fabricate jumper wires that can be used to replace the signal wire in the ECM connector for the suspect sensor. Crimp a connector socket to one end of the jumper wire.
- Disconnect the ECM connector for the suspect sensor.
- Remove the signal wire for the suspect sensor from the ECM connector.
- Install the jumper wire into the terminal location for the suspect sensor at the ECM connector.
- Connect the ECM connector.
- Check the operation of the ECM by creating an open at the ECM.
- Hold the loose end of the jumper wire away from any components in order to create an open circuit condition.
- Turn the engine control switch to the ON position.
- Monitor the active diagnostic code screen on Cat ET. Check for a 03 diagnostic code for the suspect sensor.
Note: Wait at least 30 seconds in order for the diagnostic codes to become active.
- Check the operation of the ECM by creating a short circuit at the ECM.
- Short the jumper wire for the suspect sensor to the analog return in order to create a short circuit condition.
- Monitor the active diagnostic code screen on Cat ET. Check for a 04 diagnostic code for the suspect sensor.
Note: Wait at least 30 seconds in order for the diagnostic codes to become active.
- Turn the engine control switch to the OFF position.
- Remove all jumper wires. Return the wiring to the original configuration.
Expected Result:
A 03 diagnostic code is active when the sensor signal wire is removed from the ECM connector. A 04 diagnostic code is active when the signal wire is shorted to the analog return.
Results:
- OK - The ECM is operating properly. The problem is in the wiring between the ECM and the connector for the sensor.
Repair: If the code is active for more than one sensor, the problem is most likely in the return wire for the sensor. Repair the analog return wire for the sensor or replace the harness.If the code is only active for one sensor, the problem is most likely in the signal wire for the sensor. Repair the signal wire for the sensor.
STOP
- Not OK - One of the following conditions exists: The 03 diagnostic code is not active when the sensor signal wire is disconnected. The 04 diagnostic code is not active when the wire jumper is shorted to the analog return.
Repair: Replace the ECM. Refer to Troubleshooting, "ECM - Replace". Verify that the problem is resolved.
STOP