C27 and C32 Engines for Caterpillar Built Machines Caterpillar

Use this procedure to troubleshoot the electrical system if a problem is suspected with the sensors. Also use this test procedure if any one of the diagnostic codes in Table 1 is active or easily repeated.

Table 1

Diagnostic Codes Table
CDL Code and Description	Conditions which Generate this Code	System Response
100-3 Engine Oil Pressure Sensor : Voltage Above Normal	The Electronic Control Module (ECM) detects signal voltage that is not in the acceptable range.	The code is logged. The value of the parameter is set to a default value.
100-4 Engine Oil Pressure Sensor : Voltage Below Normal	The ECM detects signal voltage that is not in the acceptable range.	The code is logged. The value of the parameter is set to a default value.
101-3 Crankcase Air Pressure Sensor : Voltage Above Normal	The ECM detects signal voltage that is not in the acceptable range.	The code is logged. The value of the parameter is set to a default value.
101-4 Crankcase Air Pressure Sensor : Voltage Below Normal	The ECM detects signal voltage that is not in the acceptable range.	The code is logged. The value of the parameter is set to a default value.
274-3 Atmospheric Pressure Sensor : Voltage Above Normal	The ECM detects signal voltage that is not in the acceptable range.	The code is logged. The value of the parameter is set to a default value.
274-4 Atmospheric Pressure Sensor : Voltage Below Normal	The ECM detects signal voltage that is not in the acceptable range.	The code is logged. The value of the parameter is set to a default value.
460-3 Fuel Pressure Sensor - After Fuel Filter : Voltage Above Normal	The ECM detects signal voltage that is not in the acceptable range.	The code is logged. The value of the parameter is set to a default value.
460-4 Fuel Pressure Sensor - After Fuel Filter : Voltage Below Normal	The ECM detects signal voltage that is not in the acceptable range.	The code is logged. The value of the parameter is set to a default value.
460-21 Fuel Pressure Sensor - After Fuel Filter : Data Drifted Low	The ECM determined that the supply voltage is not present at the fuel pressure sensor.	The code is logged. The sensor is set to the default value.
827-3 Left Exhaust Temperature Sensor : Voltage Above Normal	The ECM detects signal voltage that is not in the acceptable range.	The code is logged. The value of the parameter is set to a default value.
827-4 Left Exhaust Temperature Sensor : Voltage Below Normal	The ECM detects signal voltage that is not in the acceptable range.	The code is logged. The value of the parameter is set to a default value.
828-3 Right Exhaust Temperature Sensor : Voltage Above Normal	The ECM detects signal voltage that is not in the acceptable range.	The code is logged. The value of the parameter is set to a default value.
828-4 Right Exhaust Temperature Sensor : Voltage Below Normal	The ECM detects signal voltage that is not in the acceptable range.	The code is logged. The value of the parameter is set to a default value.
1785-3 Intake Manifold Pressure Sensor : Voltage Above Normal	The ECM detects signal voltage that is not in the acceptable range.	The code is logged. The value of the parameter is set to a default value.
1785-4 Intake Manifold Pressure Sensor : Voltage Below Normal	The ECM detects signal voltage that is not in the acceptable range.	The code is logged. The value of the parameter is set to a default value.
1785-21 Intake Manifold Pressure Sensor : Data Drifted Low	The ECM determined that the supply voltage is not present at the intake manifold pressure sensor.	The code is logged. The sensor is set to the default value.
2350-3 Left Exhaust #2 Temperature : Voltage Above Normal	The ECM detects signal voltage that is not in the acceptable range.	The code is logged. The value of the parameter is set to a default value.
2350-4 Left Exhaust #2 Temperature : Voltage Below Normal	The ECM detects signal voltage that is not in the acceptable range.	The code is logged. The value of the parameter is set to a default value.
2351-3 Right Exhaust #2 Temperature : Voltage Above Normal	The ECM detects signal voltage that is not in the acceptable range.	The code is logged. The value of the parameter is set to a default value.
2351-4 Right Exhaust #2 Temperature : Voltage Below Normal	The ECM detects signal voltage that is not in the acceptable range.	The code is logged. The value of the parameter is set to a default value.
2738-3 Turbocharger #1 Compressor Inlet Pressure Sensor : Voltage Above Normal	The ECM detects signal voltage that is not in the acceptable range.	The code is logged. The value of the parameter is set to a default value.
2738-4 Turbocharger #1 Compressor Inlet Pressure Sensor : Voltage Below Normal	The ECM detects signal voltage that is not in the acceptable range.	The code is logged. The value of the parameter is set to a default value.
3385-3 EGR Intake Pressure Sensor : Voltage Above Normal	The ECM detects signal voltage that is not in the acceptable range.	The code is logged. The value of the parameter is set to a default value.
3385-4 EGR Intake Pressure Sensor : Voltage Below Normal	The ECM detects signal voltage that is not in the acceptable range.	The code is logged. The value of the parameter is set to a default value.
3385-21 EGR Intake Pressure Sensor : Data Drifted Low	The ECM determined that the supply voltage is not present at the NRS absolute pressure sensor.	The code is logged. The sensor is set to the default value.
3387-3 Engine Exhaust Gas Recirculation Differential Pressure Sensor : Voltage Above Normal	The ECM detects signal voltage that is not in the acceptable range.	The code is logged. The value of the parameter is set to a default value.
3387-4 Engine Exhaust Gas Recirculation Differential Pressure Sensor : Voltage Below Normal	The ECM detects signal voltage that is not in the acceptable range.	The code is logged. The value of the parameter is set to a default value.

The supply voltage is routed to terminal 1 of each sensor connector. The sensor return is routed to terminal 2 of each sensor connector. For the pressure sensors, the sensor signal is routed to terminal 3 of each sensor connector. The sensor signal for the exhaust temperature sensors is routed to terminals 3 and 4 of the connector for the sensor buffer.

The ECM provides short circuit protection for the internal power supply. A short circuit to the battery will not damage the internal power supply.

Diagnostic Testing using Caterpillar Electronic Technician (ET)

Wiggle Test - The wiggle test allows the technician to monitor the status of the signals from the sensors. For additional information regarding the wiggle test, refer to the documentation that accompanies the Cat ET software.

Illustration 1	g02151686
Schematic for the active sensors

Table 2

Troubleshooting Test Steps	Values	Results
1. Check for Codes A. Connect Cat® Electronic Technician (ET) to the service tool connector. B. Look for the following codes that are active or logged: · -3 · -4 · -21	Codes	Result: A -3 diagnostic code is active. Proceed to Test Step 2. Result: A -4 diagnostic code is active. Proceed to Test Step 3. Result: A -10 or -21 diagnostic code is active. Repair: Both the -10 and -21 diagnostic codes indicate that the sensor is not receiving the correct supply voltage. Refer to Troubleshooting, "Sensor Supply - Test" for information that is related to troubleshooting the supply circuit for the suspect sensor. If the repair does not resolve the problem, proceed to Test Step 2.
2. Create a Short at the Sensor Connector A. Use a test lamp in order to create a short between terminal 3 (signal) and terminal 2 (return) at the sensor connector. B. Turn the keyswitch to the ON position. C. Monitor the diagnostic codes on Cat ET. Check for an active -4 diagnostic code for the suspect sensor. D. Turn the keyswitch to the OFF position.	-4 Code	Result: A -4 diagnostic code became active after creating the short at the sensor connector. Repair: The wiring is OK. Replace the sensor. Verify that the problem is resolved. If the repair does not resolve the problem, proceed to Test Step 3. Result: The -3 diagnostic code remains active for the suspect sensor. Proceed to Test Step 4.
3. Create an Open at the Suspect Sensor Connector A. Turn the keyswitch to the OFF position. B. Disconnect the sensor connector of the suspect sensor with the active -4 diagnostic code. C. Turn the keyswitch to the ON position. D. Monitor the diagnostic codes on Cat ET. Check for an active -3 diagnostic code for the suspect sensor. E. Turn the keyswitch to the OFF position.	-3 Code	Result: A -3 diagnostic code became active after disconnecting the sensor. Repair: The wiring is OK. Replace the sensor. Verify that the problem is resolved. If the repair does not resolve the problem, proceed to Test Step 4. Result: The -4 diagnostic code remains active for the suspect sensor. Proceed to Test Step 4.
4. Check the 5V Supply Voltage at the Sensor Connector A. Turn the keyswitch to the ON position. B. Measure the voltage between pin 1 (analog supply) and pin 2 (analog return).	5.0 ± 0.2 VDC	Result: The supply voltage is approximately 5.0 ± 0.2 VDC. Proceed to Test Step 5. Result: The supply voltage is not approximately 5.0 ± 0.2 VDC. Repair: There is a short circuit to battery voltage in the wiring harness. Repair the wiring or replace the harness. Verify that the problem is resolved. If the repair does not resolve the problem, proceed to Test Step 5.
5. Perform the Wiggle Test on the Suspect Harness A. Turn the keyswitch to the ON position. B. Use Cat ET to start the wiggle test. C. Slowly wiggle the wiring and the connectors between each of the ECM connectors and the sensor. Pay particular attention to the wiring near each connector. Be sure to wiggle all of the wiring. As you wiggle the wiring look for these problems: · Loose connectors or damaged connectors · Moisture on the connectors or the wiring · Damage that is caused by excessive heat · Damage that is caused by chafing · Improper routing of wiring · Damaged insulation	Wiggle Test	Result: The wiring passed the wiggle test. Repair: There may be an intermittent problem in the harness or in a connector. Recheck each segment of the wiring harness. Refer to Troubleshooting, "Electrical Connectors - Inspect" for information that is related to the inspection of wiring and connectors. If the wiring appears to be OK, perform the following procedure: 1. Turn the keyswitch to the OFF position. 2. Disconnect the connectors. Carefully inspect the terminals for proper installation. Ensure that each terminal in the connector is clean and dry. 3. Insert a pin into each socket. Verify that each socket grips the pin firmly. Repair any problems. 4. Connect all connectors. 5. Verify that the problem is resolved. Result: The wiggle test identified a problem in the harness. Repair: There is a problem with the wiring. Repair the wiring or replace the wiring. Verify that the repair eliminated the problem.