HOSE-AIR 2603540 - Caterpillar

Illustration 12 g01240891
Sensor connector (Terminal 1) Sensor supply (Terminal 2) Sensor return (Terminal 3) Signal
Illustration 13 g01159881
Connector for the ambient air temperature sensor (Terminal 1) Sensor supply (Terminal 2) Sensor return (Terminal 3) Signal
Table 2
Troubleshooting Test Steps    Values    Results    
1. Check for an Active Diagnostic Code
A. Connect Caterpillar Electronic Technician (ET) to the service tool connector.
B. Monitor the diagnostic codes on Cat ET. Check and record any diagnostic codes.
Note: Wait at least 30 seconds in order for the diagnostic codes to become active.
C. Determine if a diagnostic code has been logged several times.
Note: A diagnostic code that is logged several times is an indication of an intermittent problem. Most intermittent problems are the result of a bad connection between a socket and a pin in a connector or a bad connection between a wire and a crimp connection.
D. Look for one or more of the following diagnostic codes that are active or logged:
- 91-8
- 171-3
- 171-4
- 171-8
- 1491-3
- 1491-4
- 1491-8
- 1492-3
- 1492-4
- 1492-8
    Active Codes    
Results: No diagnostic codes are active.
Repair: If one of the codes listed are logged, there may be an intermittent problem in the harness or in a connector. If an intermittent electrical problem is suspected, refer to Troubleshooting, "Electrical Connectors - Inspect" for the correct procedures for inspecting electrical connectors.
Results: One of the diagnostic codes listed are active.
Repair: The ECM detects a problem in one of the circuits for the PWM sensors.
Proceed to Test Step 2.
   
2. Check the Digital Supply Voltage at the Sensor Connector
A. Remove the electrical power from the ECM.
B. Disconnect the suspect sensor at the sensor connector.
C. Restore the electrical power to the ECM.
D. Measure the supply voltage on the harness side of the sensor connector. Measure the voltage between the terminal that is for the supply voltage and the terminal that is for the return.
    8.0 0.4 VDC    
Results: The supply voltage is 8.0 0.4 VDC. The supply voltage is reaching the sensor connector.
Proceed to Test Step 4.
Results: The supply voltage is not 8.0 0.4 VDC. The supply voltage is not reaching the sensor connector.
Proceed to Test Step 3.
   
3. Check the Digital Supply Voltage at the Supply
A. Remove the electrical power from the ECM.
B. Disconnect the J2/P2 ECM connectors.
C. Fabricate two jumper wires that are long enough to use as test leads at the ECM connector. Crimp connector sockets to one end of each of the jumper wires.
D. Remove the wires for the digital supply from terminal locations P2-29 and P2-92. Install a jumper wire into each of these terminal locations.
E. Connect the J2/P2 ECM connectors.
F. Restore the electrical power to the ECM.
G. Measure the voltage between the jumper wires that are in terminals P2-29 and P2-92.
H. Remove the electrical power from the ECM.
I. Restore the wiring to the original configuration.
    8.0 0.4 VDC    
Results: The supply voltage at the ECM is 8.0 0.4 VDC.
Repair: The supply voltage at the ECM is correct. There is a problem in the