3516C High Displacement Engine Caterpillar

Use this procedure to troubleshoot the electrical system if a problem is suspected with the sensor that is for the turbocharger turbine inlet temperature. Or, use this procedure if one of the following diagnostic codes is active or easily repeated.

Table 1

J1939 Code and Description	CDL Code and Description	Comments
91-3 Accelerator Pedal Position #1 : Voltage Above Normal	91-3 Throttle Position Sensor : Voltage Above Normal	The Electronic Control Module (ECM) detects a voltage that is above normal in the circuit for the throttle position sensor.
91-4 Accelerator Pedal Position #1 : Voltage Below Normal	91-4 Throttle Position Sensor : Voltage Below Normal	The ECM detects a voltage that is below normal in the circuit for the throttle position sensor.
91-8 Accelerator Pedal Position #1 : Abnormal Frequency, Pulse Width, or Period	91-8 Throttle Position Sensor : Abnormal Frequency, Pulse Width, or Period	The ECM detects an incorrect frequency or an incorrect duty cycle in the circuit for the throttle signal. The engine speed is limited to low idle.

System Operation

Use this procedure to troubleshoot any suspect problems with the sensor for the left turbocharger turbine inlet temperature or the right turbocharger turbine inlet temperature.

The Pulse Width Modulated Sensor (PWM) provides a signal to the ECM. The PWM signal is used to represent certain engine operating conditions. The sensors receive 8.0 ± 0.4 VDC from a regulated power supply.

The ECM performs an automatic calibration of these sensors whenever the ECM is powered and the engine has been off for at least 5 seconds.

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

The following components can cause problems with the power supply:

• Electrical connector or wiring

• Sensor

• ECM

The most likely cause of a problem is a problem with an electrical connector or wiring. The least likely cause is a problem with the ECM.

Illustration 1	g02723136

Table 2

Troubleshooting Test Steps	Values	Results
1. Check for Diagnostic Codes A. Turn the keyswitch to the ON position. B. Establish communication between Caterpillar Electronic Technician (ET) and the ECM. Refer to Troubleshooting, "Electronic Service Tools" if necessary. C. Look for diagnostic codes.	Diagnostic Codes	Results: A -3 code is active or logged. Proceed to Test Step 2. Results: A -4code is active or logged. Proceed to Test Step 3. Results: A -8 code is active or logged. Proceed to Test Step 5.
2. Create a Short at the Sensor Connector A. Turn the keyswitch to the OFF position. B. Use a jumper wire in order to create a short between terminal 3 (signal) and terminal 2 (sensor return) at the sensor connector. C. Turn the keyswitch to the ON position. D. Monitor the diagnostic codes on Cat ET. Check for an active -4 diagnostic code for the suspect sensor.	Short Created	Results: A -4 diagnostic code became active after creating the short at the sensor connector. The wiring is OK. Repair: Replace the sensor. Verify that then problem is resolved. Results: 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.	Create an Open	Results: A -3 diagnostic code became active after disconnecting the sensor. The wiring is OK. Repair: Replace the sensor. Verify that then problem is resolved. Results: A -3 diagnostic code did not become active after disconnecting the sensor. Proceed to Test Step 4.
4. Check the 8 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	Results: The supply voltage is approximately 8.0 ± 0.2 VDC. Connect the sensor and then proceed to Test Step 8. Results: The supply voltage is not approximately 8.0 ± 0.2 VDC. There is a short in the harness to the battery. Repair: Repair the wiring or replace the harness. Verify that the problem is resolved. Return to Service.
5. Check the PWM Circuit for an Open A. Turn the keyswitch to the OFF position. B. Disconnect the sensor connector of the suspect sensor with the active -8 diagnostic code. C. Disconnect the J2 connector at the ECM. D. Measure the resistance between the suspect sensor PWM signal wire (pin 3 on the sensor connector) and the appropriate PWM signal wire on the ECM connector. Refer to the appropriate schematic.	Open Circuit	Results: Less than 10 ohms of resistance between the sensor connector and the ECM connector. Proceed to Test Step 6. Results: More than 10 ohms of resistance between the sensor connector and the ECM connector. There is an open circuit in the wiring harness. Repair: Repair the wiring or replace the harness. Verify that the problem is resolved. Return to Service.
6. Check the PWM Circuit for a Short Circuit A. Turn the keyswitch to the OFF position. B. Disconnect the sensor connector of the suspect sensor with the active -8 diagnostic code. C. Disconnect the J2 connector at the ECM. D. Measure the resistance between the suspect sensor PWM signal wire (pin 3 on the sensor connector) and ground.	Short Circuit	Results: There was more than 100 K ohms of resistance between pin 3 and ground. Proceed to Test Step 7. Results: There was less than 100 K ohms of resistance between pin 3 and ground. There is a short circuit in the wiring harness. Repair: Repair the wiring or replace the harness. Verify that the problem is resolved. Return to Service.
7. Check the PWM Circuit for a Pin to Pin Short Circuit A. Turn the keyswitch to the OFF position. B. Disconnect the sensor connector of the suspect sensor with the active -8 diagnostic code. C. Disconnect the J2 connector at the ECM. D. Measure the resistance between the suspect sensor PWM signal wire (pin 3 on the sensor connector) and ground.	Short Circuit	Results: There was more than 100 K ohms of resistance between the signal pin at the ECM and all other pins in the ECM connector. Proceed to Test Step 8. Results: There was less than 100 K ohms of resistance between the signal pin at the ECM and all other pins in the ECM connector. There is a short circuit in the wiring harness. Repair: Repair the wiring or replace the harness. Verify that the problem is resolved. Return to Service.
8. 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 by excessive heat. 4. Damage that is caused by chafing. 5. Improper routing of wiring. 6. Damaged insulation.	Test passed	Results: The wiring failed the Wiggle Test. There is a problem with the wiring. Repair: Repair the wiring or replace the wiring. Verify that the problem is resolved. Return to service. Results: The wiring passed the Wiggle Test. The problem may be intermittent. Inspect the wiring. Refer to Troubleshooting, "Electrical Connectors - Inspect". If the wiring looks OK perform the following procedure. 1. Turn the keyswitch to the OFF position. 2. Disconnect the connectors. Carefully inspect the terminals for proper installation. 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. 6. Return the unit to service.