GENERATOR GP 2681181 - Caterpillar

The ECM continuously creates a pull-up voltage on the signal wire for each sensor. The ECM uses this pull-up voltage 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 . When the ECM detects voltage that is below a threshold on the signal wire, the ECM activates a low voltage -4 diagnostic .Note: There may be a delay of 30 seconds in order for Cat® Electronic Technician (ET) to display an active diagnostic . When you check for a diagnostic , be sure to wait at least 30 seconds.
Illustration 1 g06120200
For the complete circuit details, refer to the full schematic.
Table 2
Troubleshooting Test Steps Values Results
1. Check for Codes
A. Connect Cat® Electronic Technician (ET) to the service tool connector.
B. Determine if a code is active or logged.
Codes
Result: A -3 code is active.
Proceed to Test Step 2.
Result: A -4 code is active.
Proceed to Test Step 3.
2. Create a Short at the Sensor Connector
A. Turn the keyswitch to the OFF position.
B. Disconnect the sensor with the active -3 code.
C. Install the jumper wire between the following terminals at the sensor connector:
- Terminal 3 (signal) and Terminal 2 (sensor return)
D. Connect Cat ET.
E. Use Cat ET to monitor the following:
- -4 code
F. Turn the keyswitch to the OFF position.
Create a Short
Result: A -4 code did not become active.
Proceed to Test Step 4.
Result: A -4 code became active.
Repair: The wiring harness is OK. Replace the sensor.
Verify that the repair eliminated the problem.
3. Create an Open at the Sensor Connector
A. Turn the keyswitch to the OFF position.
B. Disconnect the sensor with the active -4 code.
C. Connect Cat ET.
D. Use Cat ET to monitor the following:
- -3 code
E. Turn the keyswitch to the OFF position.
Create an Open
Result: A -3 code did not become active.
Proceed to Test Step 4.
Result: A -3 code became active.
Repair: The wiring harness is OK. Replace the sensor.
Verify that the repair eliminated the problem.
4. Check the 5 VDC Supply Voltage at the Sensor Connector
A. Turn the keyswitch to the ON position.
B. Measure the voltage at the sensor connector between the following pins:
- Pin 1 and Pin 2
C. Reconnect the sensor.
5.0 0.2 VDC
Result: The supply voltage is 5.0 0.2 VDC.
Proceed to Test Step 5.
Result: The supply voltage is not 5.0 0.2 VDC.
Repair:Repair or replace the wiring harness.
If the problem is not resolved, proceed to Test Step 5.
5. Perform the Wiggle Test
Carefully following this procedure is the best way to identify the root cause of an intermittent problem.
A. Connect Cat ET.
B. Use CAT ET to perform the following test:
- "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 the wiring.
As you wiggle the wiring look for these problems:
- Loose connectors or damaged connectors
- Moisture on the connectors or the wiring
- Damaged that is caused by excessive heat
- Damage that is