C32 Generator Set Engines Caterpillar

Speed Control - Test

Usage:

C32 TZJ

Use this procedure to troubleshoot a problem with the throttle position sensor. Also, use this procedure if one of the following diagnostic codes is active or easily repeated.

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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 signal voltage that is not in the acceptable range. The code is logged. The ECM flags the throttle position as invalid data and a default value is used. The engine speed is limited to high idle.
91-4 Accelerator Pedal Position #1 : Voltage Below Normal	91-4 Throttle Position Sensor : Voltage Below Normal	The ECM detects signal voltage that is not in the acceptable range. The code is logged. The ECM flags the throttle position as invalid data and a default value is used. The engine speed is limited to high idle.
91-8 Accelerator Pedal Position #1 : Abnormal Frequency, Pulse Width, or Period	91-8 Throttle Position Sensor : Abnormal Frequency, Pulse Width, or Period	The PWM signal from the sensor to the ECM is not correct. The code is logged.

Note: Performing steps within this procedure requires the use of a multimeter capable of measuring a PWM duty cycle and frequency. Refer to Table 2 for the tools recommended for the procedure.

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Table 2
Recommended Tools
146-4080 Digital Multimeter Gp
7X-1710 Multimeter Probe
326-4904 Adapter Cable As

The Electronic Control Module (ECM) can be configured to receive two different types of throttle signals for the engine throttle control:

CAN Input - A J1939 signal is received via the CAN data link.
PWM - The Pulse Width Modulated signal (PWM) must be received via terminal P1-66 at the ECM connector. If direct fuel control mode is used on the engine, the PWM signal must be received via terminal P1-66 at the ECM connector.

The ECM also allows a primary throttle and a secondary throttle to be configured for the engine if direct fuel control mode is disabled. The type of signal that will be used for the primary throttle is configured by setting the "Desired Speed Input Configuration" parameter. The type of signal that will be used for the secondary throttle is configured by setting the "Secondary Desired Speed Input Configuration" parameter. Configuring both of these parameters to the same setting will invalidate the setting for the secondary throttle.

The ECM will utilize the signal that is defined as the primary throttle as long as a valid signal is available from the expected source. If the signal from the primary throttle becomes unavailable, the ECM will use the signal that is defined as the secondary throttle. If both throttle signals become unavailable, the ECM uses the rated speed of the engine as the setpoint for the desired engine speed.

For using an electronic external governor for engine control, the "Direct Fuel Control Mode" parameter must be enabled. The ECM input at P1-66 must be used for direct fuel control of the engine. Refer to Troubleshooting, "Direct Fuel Control Mode - Test" for additional information.

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Table 3
Troubleshooting Test Steps	Values	Results
1. Inspect the Electrical Connectors and the Wiring A. Turn the main disconnect switch to the OFF position. B. Thoroughly inspect the connectors. Refer to Troubleshooting, "Electrical Connectors-Inspect" for additional information. C. Perform a 45 N (10 lb) pull test on the connector wires. D. Check the harness for abrasions and pinch points.	Connectors and Wiring	Result: The connectors and wiring appear to be OK. Proceed to Test Step 2. Result: There is a problem with the connectors and/or wiring. Repair: Repair or replace the connectors or wiring. Ensure that all the seals are properly in place and ensure that the connectors are coupled. If the problem is not resolved, proceed to Test Step 2.
2. 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 -4 code is active or logged. Proceed to Test Step 3. Result: A -3 code is active or logged. Proceed to Test Step 7.
3. Check the Wiring for an Open Circuit A. Turn the main disconnect switch to the OFF position. B. Disconnect the J1 connector from the electronic Control Module (ECM). C. Remove the signal wire at terminal 66 of the Engine Interface Connector (EIC). D. Measure the resistance between the following terminals: - P1-66 (ECM) and P1-66 (EIC)	Open Circuit	Result: There were less than 10 ohms of resistance. Proceed to Test Step 4. Result: There were more than 10 ohms of resistance. Repair: An open circuit has been detected. Repair or replace wiring harness. Verify that the repair eliminated the problem.
4. Check the Wiring Harness for a Short Circuit to Ground A. Turn the main disconnect switch to the OFF position. B. Disconnect the J1 connector from the ECM. C. Measure the resistance between the following terminals: - P1-66 (ECM) and known good ground.	Short Circuit	Result: There were less than 100 K ohms of resistance between P1-66 and a known good ground. Proceed to Test Step 5. Result: There were more than 100 K ohms of resistance on each wire and a known good ground. Repair: A short circuit to ground has been detected. Repair or replace the wiring harness. Verify that the repair eliminated the problem.
5. Check the Wiring Harness for a Pin to Pin Short Circuit A. Turn the main disconnect switch to the OFF position. B. Disconnect the J1 connector from the ECM. C. Measure the resistance between the following terminals: - Pin 66 on the J1 ECM connector and all the other pins in the J1 ECM connector.	Short Circuit	Result: There were less than 100 K ohms of resistance between the pin 66 and all the pins in the J1 ECM connector. Repair: A short circuit to ground has been detected. Repair or replace the wiring harness. Verify that the repair eliminated the problem. Result: There were more than 100 K ohms of resistance between the pin 66 and all the pins in the J1 ECM connector. Repair: The problem is located outside the Cat system wiring circuit. There is an open circuit or short to ground with the wiring or a problem with the speed control device after the EIC. Proceed to Test Step 6.
6. Check the Device that Provides the Desired Engine Speed Signal A. Measure the desired engine speed signal, refer to the Original Equipment Manufacturers (OEM) service information. B. Verify that the correct signal is being provided from the device as close to the device as possible. C. Verify that the correct signal is present at Terminal 66 of the EIC.	Desired Speed Signal	Result: The speed control device is not providing the correct desired speed input signal. Repair: Repair or replace the device that is providing the desired engine speed signal, refer to the OEM service information. Refer to "Direct Fuel Control Mode - Test" for additional information regarding mA to PWM converter. Refer to Testing and Adjusting, "Calibration (175-4998 Signal Converter)" for additional information. Result: The speed control device is providing the correct desired speed input signal and the signal measured at the EIC is not correct. Repair: There is an open circuit or short to ground with the wiring in between the speed control device and the EIC. Refer to the customer system schematics or instruction for additional information. Verify that the repair eliminated the problem.
7. Check the Wiring Harness for a Short Circuit to the +Battery or Ground A. Turn the battery disconnect to the OFF position. B. Remove the wires for the desired speed from the speed control device. C. Turn the battery disconnect switch to the ON position. D. Connect Cat ET. E. Use Cat ET to monitor the following codes: - -3	Short Circuit	Results: The -3 code remains active after the signal wire is removed from the speed control device providing the desired speed signal. Proceed to Test Step 8. Results: The -3 code is no longer active and has transitioned to logged. A -4 code is now active. Repair: Repair or replace the device that is providing the desired engine speed signal, refer to the OEM service information.
8. Check the Wiring Harness for a Short Circuit to the +Battery A. Turn the battery disconnect to the OFF position. B. Remove the wire for desired speed signal from the P1-66 EIC. C. Turn the battery disconnect switch to the ON position. D. Connect Cat ET. E. Use Cat ET to monitor the following codes: - -3	Short Circuit	Result: The -3 code remains active after the signal wire is removed from the EIC. Repair: There is a short between the ECM and EIC. Repair or replace the wiring harness between the ECM and the EIC. Result: There is a short between the EIC and the speed control device. The-3 code is no longer active after the signal wire is removed from the EIC. Repair: Repair or replace the wiring harness between the EIC and the speed control device.

If the procedure did not correct the issue, contact your Cat dealer Technical Communicator (TC). For further assistance, your TC can confer with the Dealer Solutions Network (DSN).