ROD AS 9T6976 - Caterpillar

Illustration 10 g02211287
CEM (typical) (1) Absolute pressure sensor for the DPF
Illustration 11 g02145602
CEM (typical) (1) Combustion air absolute pressure sensor (2) Main fuel pressure sensor (3) Pilot fuel pressure sensor
Table 2
Troubleshooting Test Steps    Values    Results    
1. Check for Diagnostic Codes
A. Establish communication between Caterpillar 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 a -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 3251-2 diagnostic code is active.
Proceed to Test Step 6.
   
2. Create a Short at the Sensor Connector
A. Use a jumper wire 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.
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.
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.
There is a short in the harness to the battery. Repair the wiring or replace the harness
Verify that the problem is resolved.
STOP
   
5. Perform the Wiggle Test
Carefully following this procedure is the best way to identify the root cause of an intermittent problem.
A. Turn the keyswitch to the ON position.
B. Use CAT ET to run the "Wiggle Test".
C. Slowly wiggle the wiring and the connectors between the P2 connector 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.
1. Loose connectors or damaged connectors
2. Moisture on the connectors or the wiring
3. Damaged that is caused