3512B and 3512C Petroleum Generator Set Engines 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. Also, use this procedure if any one of the diagnostic codes in Table 1 is active or easily repeated.

Table 1

Diagnostic Codes Table
Description	Conditions which Generate this Code	System Response
827-8 Left Exhaust Temperature signal abnormal	The Electronic Control Module (ECM) detects a sensor frequency that is greater than 1000 Hz or less than 150 Hz. The ECM detects a duty cycle that is greater than 90 percent or a duty cycle that is less than 10 percent.	The value of the parameter is set to zero. The code is logged.
828-8 Right Exhaust Temperature signal abnormal	The ECM detects a sensor frequency that is greater than 1000 Hz or less than 150 Hz. The ECM detects a duty cycle that is greater than 90 percent or a duty cycle that is less than 10 percent.

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	g03318025
Typical schematic

Illustration 2	g03318027
Terminal locations at the P1/J1 ECM connector for the turbocharger turbine inlet temperature sensors (P1-4) Digital supply (P1-5) Digital return (P1-11) Left turbo inlet temperature (P1-12) Right turbo inlet temperature

Illustration 3	g03318055
Terminal locations at the P2/J2 ECM connector for the turbocharger turbine inlet temperature sensors (P2-54) Digital return (P2-56) Digital supply

Illustration 4	g01240891
Sensor connector (Terminal 1) Sensor supply (Terminal 2) Sensor return (Terminal 3) Signal

Illustration 5	g01234146

Table 2

Troubleshooting Test Steps	Values	Results
1. Check for an "Active" Diagnostic Codes 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 occurred 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. There could also be a bad connection between a wire and a terminal.	Codes	Results: No diagnostic codes are active. Repair: There may be an intermittent problem in the harness or in a connector. If an intermittent problem is suspected, refer to Troubleshooting, "Electrical Connectors - Inspect" for the correct procedures for inspecting electrical connectors. Results: One of the diagnostic codes that are listed above are active or logged. The ECM detects a problem in one of the circuits for the exhaust temperature sensors. Proceed to Test Step 2
2. Check the Digital Supply Voltage at the Sensor Connector A. Turn the main disconnect switch to the OFF position. 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 terminal 1 and terminal 2 for the suspect sensor.	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 ECM A. Turn the main disconnect switch to the OFF position. B. Disconnect the J2/P2 and the J1/P1 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 P1-4 and P2-56. 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 P1-4 and P2-54. H. Turn the main disconnect switch to the OFF position. 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 wiring between the ECM and the sensor connector. Repair the connectors or wiring and/or replace the connectors or wiring. Verify that the repair eliminated the problem. Results: The supply voltage is not 8.0 ± 0.4 VDC. Repair: The voltage at the ECM is not correct. There is a problem with the ECM. Replace the ECM. Refer to Troubleshooting, "Test ECM Mode". Note: Before you consider replacing the ECM, consult with the Dealer Solutions Network (DSN) for assistance. Verify that the repair eliminated the problem.
4. Check the duty cycle for the Suspect Sensor at the Sensor Connector A. Turn the main disconnect switch to the OFF position. B. Remove the sensor signal wire from terminal 3 on the sensor side of the sensor connector. C. Install a 7X-6370 Adapter Cable As (3-PIN BREAKOUT) at the sensor connector. D. Restore the electrical power to the ECM. E. Measure the duty cycle between the loose signal wire and terminal 2 (digital return) of the breakout t. Note: Set the multimeter to "VDC". Press the "Hz" button twice so that the % symbol is displayed. F. Turn the main disconnect switch to the OFF position. G. Restore the wiring to the original configuration.	Between 10 to 90 percent.	Results: The duty cycle is between 10 to 90 percent. The duty cycle is correct. Proceed to Test Step 5 Results: The duty cycle is incorrect. Repair: Replace the sensor. Verify that no diagnostic codes are active for the suspect sensor before permanently installing the sensor. Verify that the repair eliminated the problem.
5. Check the Duty Cycle for the Suspect Sensor at the ECM A. Turn the main disconnect switch to the OFF position. B. Disconnect the J1/P1 and J2/P2 ECM connectors. C. Remove the signal wire for the suspect sensor from the appropriate terminal location at the P1 and P2 ECM connectors. Refer to Illustrations 2 and 3for the terminal locations of the signal wires. D. Connect the J2/P2 ECM connectors. E. Restore the electrical power to the ECM. F. Measure the duty cycle between the sensor signal wire and the appropriate digital return at the breakout t. Note: Set the multimeter to "VDC". Press the "Hz" button twice in order to display the % symbol. G. Turn the main disconnect switch to the OFF position. H. Restore all wiring to the original configuration.	Between 10 to 90 percent	Results: The duty cycle is between 10 to 90 percent. Repair: The duty cycle is correct. The sensor is producing the correct signal. There is a problem with the ECM. Replace the ECM. Refer to Troubleshooting, "Test ECM Mode". Note: Before you consider replacing the ECM, consult with the Dealer Solutions Network (DSN) for assistance. Results: The duty cycle is not correct. Repair: The sensor signal is OK at the sensor connector, but the sensor signal is not reaching the ECM. There is a problem in the wiring between the sensor connector and the ECM. Repair the connectors and/or wiring between the sensor connector and the ECM. Verify that the repair eliminated the problem.