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 | ||
|---|---|---|
| Description | Conditions which Generate this Code | System Response |
| 94-3 Fuel Delivery Pressure Sensor voltage above normal | The Electronic Control Module (ECM) detects signal voltage that is above normal for eight seconds.
The engine has been running for two seconds. Absolute pressures that are greater than |
The code is logged.
A snapshot is triggered. The value of the parameter will be set to |
| 94-4 Fuel Delivery Pressure Sensor voltage below normal | The ECM detects signal voltage that is below normal for 180 seconds.
The engine has been running for two seconds. A barometric pressure of less than |
|
| 100-3 Engine Oil Pressure Sensor voltage above normal | The ECM detects signal voltage that is above normal for eight seconds.
The ECM has been powered for at least two seconds. |
|
| 100-4 Engine Oil Pressure Sensor voltage below normal | The ECM detects signal voltage that is above normal for eight seconds.
The ECM has been powered for at least two seconds. |
|
| 164-2 Injection Actuation Pressure Sensor signal erratic | The ECM detects signal voltage that is inconsistent. | The code is logged.
A snapshot is triggered. The value of the parameter will be set to The engine will run on a default torque map that is stored in the ECM. The engine will experience a reduction in power. |
| 164-3 Injection Actuation Pressure Sensor voltage above normal | The ECM detects signal voltage that is above normal for one second. | |
| 164-4 Injection Actuation Pressure Sensor voltage below normal | The ECM detects signal voltage that is below normal for one second. | |
| 274-3 Atmospheric Pressure Sensor voltage above normal | The ECM detects signal voltage that is above normal for thirty seconds.
The ECM has been powered for two seconds. Absolute pressures that are greater than |
The code is logged.
A snapshot is triggered. The value of the parameter will be set to the value from a map dependent value that is stored in the ECM. A ten percent derate is subtracted from the engine power. |
| 274-4 Atmospheric Pressure Sensor voltage below normal | The ECM detects signal voltage that is above normal for thirty seconds.
The ECM has been powered for two seconds. |
|
| 1785-3 Intake Manifold Pressure Sensor voltage above normal | The ECM detects signal voltage that is above normal for two seconds.
The ECM has been powered for two seconds. One of the following conditions must be satisfied: Engine speed equals zero rpm. or The engine load is less than 50 percent. |
The code is logged.
A snapshot is triggered. The value of the parameter will be set to |
| 1785-4 Intake Manifold Pressure Sensor voltage below normal | The ECM detects signal voltage that is below normal for two seconds.
The ECM has been powered for two seconds. |
|
| 1835-3 Auxiliary Pressure Sensor voltage above normal | The ECM detects signal voltage that is above normal. | The code is logged.
A snapshot is triggered. The value of the parameter will be set to a default value. |
| 1835-4 Auxiliary Pressure Sensor voltage below normal | The ECM detects signal voltage that is below normal. | |
System Operation
Use this procedure to troubleshoot any suspect problems with the following sensors:
- Atmospheric pressure sensor
- Engine oil pressure sensor
- Fuel pressure sensor
- Injection actuation pressure sensor
- Intake manifold pressure sensor
- Auxiliary Pressure Sensor
Background Information
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
- ECM
The 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.
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| Illustration 1 | g01382566 |
|
Schematic for the analog sensors | |
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| Illustration 2 | g01388316 |
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Component locations for the analog sensors (Typical left side engine view) (1) Intake manifold pressure sensor (2) Atmospheric pressure sensor (3) Fuel pressure sensor (4) Injection actuation pressure sensor (5) Engine oil pressure sensor (6) J2/P2 ECM connector (7) J1/P1 ECM connector | |
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| Illustration 3 | g01339473 |
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Terminal locations at the P2 ECM connector for the analog sensors (P2-15) Intake manifold pressure (P2-17) Sensor return (P2-28) Engine oil pressure (P2-40) Fuel pressure (P2-54) Analog return (P2-57) Atmospheric pressure (P2-72) Sensor supply (P2-80) Analog supply (P2-85) Injection actuation pressure | |
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| Illustration 4 | g01339471 |
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Terminal locations at the P1 ECM connector for the analog sensors (P1-2) Sensor supply (P1-3) Sensor return (P1-15) Auxiliary pressure (if equipped) | |
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| Illustration 5 | g01389161 |
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Terminals at the customer connector that are associated with the auxiliary pressure sensor (14) Sensor supply (15) Sensor return (33) Auxiliary pressure (if equipped) | |
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| Illustration 6 | g01159881 |
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Terminal locations at the sensor connector (Terminal A) Sensor supply (Terminal B) Sensor return (Terminal C) Signal | |
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The connection of any electrical equipment and the disconnection of any electrical equipment may cause an explosion hazard which may result in injury or death. Do not connect any electrical equipment or disconnect any electrical equipment in an explosive atmosphere. |
Test Step 1. Determine if the Code is Logged or Active
- Connect Cat ET to the service tool connector.
- Restore electrical power to the engine ECM.
- Monitor the active diagnostic code and the logged diagnostic codes on Cat ET.
Note: Wait at least 30 seconds in order for diagnostic codes to become active.
Identify the diagnostic code.
Results:
- Logged code -
Repair: Do not troubleshoot a logged code unless the code relates to an operator complaint. If the code is logged and the code does not relate to an operator complaint, clear the code.
If the code is logged and the code relates to an operator complaint, check the integrity of the connections at the connectors.
STOP
- Active code - Proceed to Test Step 2.
Test Step 2. Check the Supply Voltage at the Sensor Connector
Measure the voltage between terminal A (sensor supply) and terminal B (sensor return) at the harness connector for the sensor that relates to the code.
Expected Result:
The voltage is between 4.5 VDC and 5.5 VDC.
Results:
- OK - The voltage is between 4.5 VDC and 5.5 VDC. The supply voltage is at the sensor connector. Record the voltage measurement. If you are troubleshooting a -3 diagnostic code, proceed to Test Step 3. If you are troubleshooting a -4 diagnostic code, proceed to Test Step 6.
- Not OK - The voltage is less than 4.5 VDC or the voltage is greater than 5.5 VDC.
Repair: The voltage of the sensor supply is incorrect. Refer to Troubleshooting, "Sensor Supply - Test".
STOP
Test Step 3. Check for Battery Voltage on the Signal Wire
Measure the voltage between the signal terminal and the return terminal on the harness connector for the sensor that relates to the diagnostic code.
Expected Result:
The voltage measurement is less than the +Battery voltage.
Results:
- OK - The voltage measurement is less than the +Battery voltage. The signal wire is not shorted to the +Battery. Proceed to Test Step 4.
- Not OK - The voltage measurement is approximately equal to the +Battery voltage. The signal wire is shorted to the +Battery.
Repair: Repair the wiring, when possible. Replace parts, if necessary. Verify that the problem is resolved.
STOP
Test Step 4. Check the Signal Wire for an Open Circuit
- Disconnect the sensor that relates to the diagnostic code.
- Connect a jumper wire between the signal terminal and the return terminal on the harness connector for the sensor that relates to the diagnostic code. This will replace the sensor with a short circuit.
- Look for a -4 diagnostic code.
Expected Result:
The -3 code does not change to a -4 code when the jumper wire is connected.
Results:
- OK - The -3 code does not change to a -4 code when the jumper wire is connected. Connect the sensor. There is a problem with the wiring harness or with the ECM. Proceed to Test Step 5.
- Not OK - The -3 code changes to a -4 code when the jumper wire is connected. The wiring harness and the ECM are OK.
Repair: Perform the following procedure:
- Remove the jumper wire.
- Connect a new sensor to the engine harness. Do not install the sensor into the engine.
- Verify that the active -3 diagnostic code does not recur.
- Install the sensor into the engine.
- Clear all logged diagnostic codes and return the engine to service.
STOP
Test Step 5. Check the ECM for Proper Operation
- Determine the terminal location at the appropriate ECM connector for the signal wire of the suspect sensor. Also, determine the terminal location at the appropriate ECM connector for the return wire of the suspect sensor.
- Remove the signal terminal and the return terminal from the ECM connector.
- Install a jumper wire between the terminal locations for the signal and the return at the ECM connector. This will replace the engine wiring with a short circuit.
- Look for a -4 diagnostic code.
Expected Result:
A -4 code is active when the jumper wire is installed.
Results:
- OK - A -4 code is active when the jumper wire is installed. The ECM detected the jumper wire at the ECM connector. However, the ECM did not detect the jumper wire at the harness connector for the sensor. There is an open circuit in the wiring.
Repair: Repair the wiring, when possible. Replace parts, if necessary. Verify that the problem is resolved.
STOP
- Not OK - A -4 code is not active when the jumper wire is installed.
Repair: The ECM does not detect the short circuit at the ECM connector. There is a problem with the ECM. Perform the following procedure:
- Temporarily connect a test ECM.
Refer to Troubleshooting, "ECM - Replace ".
- Recheck the circuit in order to ensure that the original problem has been resolved.
If the problem is resolved with the test ECM, install the suspect ECM. If the problem returns with the suspect ECM, replace the ECM. Verify that the problem is resolved.
If the problem is not resolved with the test ECM, install the original ECM. There is a problem in the wiring.
STOP
- Temporarily connect a test ECM.
Test Step 6. Check the Signal Wire for a Short Circuit
- Disconnect the sensor that applies to the -4 diagnostic code.
- Look for a -3 diagnostic code.
- Connect the sensor and look for a -4 diagnostic code.
Expected Result:
When the sensor is disconnected, the -4 code remains.
Results:
- OK - When the sensor is disconnected, the -4 code remains. There is a problem with the wiring harness or with the ECM. Proceed to Test Step 7.
- Not OK - When the sensor is disconnected, the -4 code changes to a -3 code. The harness and the ECM are OK. There is a problem with the sensor.
Repair: Perform the following procedure:
- Connect a new sensor to the engine harness. Do not install the sensor into the engine.
- Verify that the active -4 diagnostic code does not recur.
- Install the sensor into the engine.
- Clear all logged diagnostic codes and return the engine to service.
STOP
Test Step 7. Check the ECM for Proper Operation
- Determine the terminal location at the appropriate ECM connector for the signal wire of the suspect sensor.
- Remove the signal wire from the ECM connector.
- Check if the -4 diagnostic code becomes an active -3 active code.
Expected Result:
A -3 code is active when the signal wire is disconnected from the ECM connector.
Results:
- OK - A -3 code is active when the signal wire is disconnected from the connector at the ECM. The ECM detected the open circuit at the ECM connector. However, the ECM did not detect the open circuit at the harness connector for the sensor. There is a problem with the wiring between the ECM connector and the harness connector for the sensor. There may be a problem with a connector.
Repair: Repair the wiring or the connector, when possible. Replace parts, if necessary. Verify that the problem is resolved.
STOP
- Not OK - A -3 code is not active when the signal wire is disconnected from the ECM connector. The ECM did not detect the open circuit at the ECM connector. There is a problem with the ECM.
Repair: The ECM does not detect the open circuit at the ECM connector. There is a problem with the ECM. Perform the following procedure:
- Temporarily connect a test ECM.
Refer to Troubleshooting, "ECM - Replace".
- Recheck the circuit in order to ensure that the original problem has been resolved.
If the problem is resolved with the test ECM, install the suspect ECM. If the problem returns with the suspect ECM, replace the ECM. Verify that the problem is resolved.
If the problem is not resolved with the test ECM, install the original ECM. There is a problem in the wiring.
STOP
- Temporarily connect a test ECM.