ELECTRONICS GP-ENGINE RATINGS 3792105 - Caterpillar

Illustration 10 g03781429
CEM (typical)
(11) Combustion air absolute pressure sensor
(12) Main fuel pressure sensor
(13) Pilot fuel pressure sensor
Table 2
Troubleshooting Test Steps Values Results
1. Check for Diagnostic Codes
A. Establish communication between Cat® Electronic Technician (ET) and the ECM . Refer to Troubleshooting, "Electronic Service Tools", if necessary.
B. Turn the keyswitch to the ON position.
C. Look for "-3", or " -4" active or logged codes.
Diagnostic Code
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 2458-2 or a 3251-2 diagnostic code is active.
Proceed to Test Step 6.
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 (sensor 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.
Short Created
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.
Result: A -4 diagnostic code does not become 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.
Create an Open
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.
Result: A -3 diagnostic code did not became active after disconnecting the sensor.
Proceed to Test Step 4.
4. Check the 5 VDC Supply Voltage at the Sensor Connector
A. Turn the keyswitch to the ON position.
B. Measure the voltage between pin 1 and pin 2 at the suspect sensor.
Test Passed
Result: The supply voltage is approximately 5.0 0.2 VDC
Connect the sensor and then proceed to Test Step 5
Result: The supply voltage is not approximately 5.0 0.2 VDC.
Repair: There is a short in the harness to the battery. Repair the wiring