C9.3 Marine Auxiliary and Generator Set Engine Caterpillar

Speed Control - Test

Usage:

C9.3 C93

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	Comments
28-3 Accelerator Pedal Position 3 : Voltage Above Normal	The Electronic Control Module (ECM) has detected that the analog "0–5 Volt" desired speed signal has exceeded the 4.5 volt trip point. The setting for the upper diagnostic limit has been exceeded for .6 seconds. The code is logged.
28-4 Accelerator Pedal Position 3 : Voltage Below Normal	The ECM has detected that the analog "0–5 Volt" desired speed signal is below the .5 volt trip point. The setting for the lower diagnostic limit has been exceeded for .6 seconds. The code is logged.
29-3 Accelerator Pedal Position 2 : Voltage Above Normal	The ECM has detected that the "PWM" desired speed signal is above the 95% diagnostic limit. The alarm output is activated. The code is logged.
29-4 Accelerator Pedal Position 2 : Voltage Below Normal	The ECM has detected that the "PWM" desired speed signal is below the 5% diagnostic limit. The alarm output is activated The code is logged.
29-8 Accelerator Pedal Position 2 : Abnormal Frequency, Pulse Width, or Period	The ECM has detected an erratic signal for the "PWM" desired speed signal. The alarm output is activated. The code is logged.
91-3 Accelerator Pedal Position 1 : Voltage Above Normal	The ECM detects signal voltage that is not in the acceptable range. The ECM flags the throttle position as invalid data and a default value is used. The engine speed is limited to high idle. The code is logged.
91-4 Accelerator Pedal Position 1 : Voltage Below Normal	The ECM detects signal voltage that is not in the acceptable range. The ECM flags the throttle position as invalid data and a default value is used. The engine speed is limited to high idle. The code is logged.
91-8 Accelerator Pedal Position 1 : Abnormal Frequency, Pulse Width, or Period	The PWM signal from the sensor to the ECM is not correct. The code is logged.
974-5 Remote Accelerator Pedal Position : Current Below Normal	The ECM detects signal voltage that is not in the acceptable range. The ECM flags the throttle position as invalid data and a default value is used. The engine speed is limited to high idle. The code is logged.
974-6 Remote Accelerator Pedal Position : Current Above Normal	The ECM detects signal voltage that is not in the acceptable range. The ECM flags the throttle position as invalid data and a default value is used. The engine speed is limited to high idle. The code is logged.

For this troubleshooting procedure, the "Desired Speed Input" configuration parameter can be set to "4 - 20 mA" input, "PWM" input, or "0-5 Volt"input.

The engine ECM will only monitor the status of the input signal for the PWM and 0-5 Volt desired speed inputs.

The engine ECM does not supply the power and ground for the PWM or 0-5 Volt speed control circuits.

If an external speed control source device is used, refer to that devices troubleshooting procedure.

If using the CAN desired speed input, refer to Troubleshooting, "Data Link - Test".

The value of the current, frequency, or voltage corresponds to a range of desired engine speeds between minimum high idle and maximum high idle. The "Minimum Engine High Idle Speed" and the "Maximum Engine High Idle Speed" are set with the "Service/Configuration" screen of Cat ET. For more information, refer to Troubleshooting, "Configuration Parameters".

When the idle/rated speed switch is in the Idle position, a current value of 4.0 mA, 5% duty cycle, or .5 Volts corresponds to the programmed "Minimum Engine High Idle Speed". A current value of 20.0 mA, 95% duty cycle, or 4.5 Volts corresponds to "Maximum Engine High Idle Speed". Desired speed input values within this range will vary the desired engine speed in a linear fashion between. The range will vary between "Minimum Engine High Idle Speed" and "Maximum Engine High Idle Speed".

The most likely causes of a diagnostic code for this circuit are a poor connection or a problem in a wiring harness. The next likely cause is a problem with a component. The least likely cause is a problem with the ECM.

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Illustration 1	g06205151

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Table 2
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·m (33 lb ft) 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: Any of the following codes are active or logged: - 28-4 - 29-4 - 91-4 - 91-8 Proceed to Test Step 3. Result: Any of the following codes are active or logged: Repair or replace the wiring harness. - 28-3 - 29-3 - 91-3 - 974-6 Proceed to Test Step 7. Result: A (974-5) code is active or logged. Proceed to Test Step 9.
3. Check the Wiring for an Open Circuit A. Ensure that the engine control is in the OFF/RESET position. Ensure that the electrical power is removed from the engine ECM. B. Remove the signal wire at the Engine Interface Connector (EIC), that carries the (PWM or Analog 0-5 Volt) desired speed input signal to the engine ECM Refer to Illustration 1. C. Perform one of the following: - For the 29-4, 91-4, and 91-8 disconnect the P1 connector from the ECM. - For the 28-4 diagnostic disconnect the P2 connector from the ECM. D. Measure the resistance between the following terminals at the removed ECM connector: - For the 91-8 and 91-4 codes, ECM terminal P1-66 and terminal 10 on the EIC. - For the 29-4 code, ECM terminal P1-68 and terminal 4 on the EIC. - For the 28-4 code, ECM terminal P2-41 and terminal 58 on the EIC.	Open Circuit	Result: The resistance measured less than 10 ohms. Proceed to Test Step 4. Result: The resistance measured more than 10 ohms. Repair: An open circuit has been detected. Repair or replace the wiring harness.
4. Check the Wiring for a Short Circuit to Engine Ground A. Measure the resistance between the ground strap for the ECM and the following terminals at the ECM connector. - For the 91-4 and 91-8 codes, ECM terminal P1-66 and engine ground. - For the 29-4 code, ECM terminal P1-68 and engine ground. - For the 28-4 code, ECM terminal P2-41 and engine ground. Refer to Illustration 1.	Short Circuit	Result: The resistance measured more than 100k ohms. The signal wire is not shorted to the engine ground. Proceed to Test Step 5. Result: The resistance measured less than 100k ohms. There is a short to engine ground on the signal wire. Repair: Repair or replace the wiring harness.
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 wiring harness form the ECM. C. Measure the resistance between the following ECM connector terminals: - For the 91-4 and 91-8 codes, ECM terminal P1-66 and all other pins in the ECM connector. - For the 29-4 code, ECM terminal P1-68 and all other pins in the ECM connector. - For the 28-4 code, ECM terminal P2-41 and all other pins in the ECM connector	Short Circuit	Result: One or more of the measurements were less than 100 K ohms between a connector terminals and any other terminal in the ECM connector. Repair: There is a short circuit in the wiring harness. Repair or replace the wiring harness. Result: All measurements were greater than 100 K ohms between the affected signal wire pin and all other pins in the ECM connector. Repair: The problem is located outside the Caterpillar 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, according to the literature that is provided by the OEM of the device. 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 the correct EIC terminal. - For the 91-4 and 91-8 codes, EIC terminal 10. - For the 29-4 code, EIC terminal 4. - For the 28-4 code, EIC terminal 58. Refer to Illustration 1.	Desired Speed Signal	Result: The speed control device is not providing the correct desired speed input signal. Repair: Service the device that is providing the desired engine speed signal, according to the literature that is provided by the OEM of the device. Result: The speed control device is providing the correct desired speed signal. The signal measure 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 Customer system schematics or instruction for additional information. Verify that the repair eliminated the problem.
7. Check the Wiring for a Short Circuit to the +Battery or Ground A. Remove the wires for the desired speed from the speed control device. B. Turn the battery disconnect switch to the ON position. C. Observe Cat ET for a diagnostic FMI state change.	Short Circuit	Result: The -3 or -6 code remains active after the signal wire is removed from the speed control device providing the desired speed signal. Proceed to Test Step 8. Result: The -3 or -6 code is no longer active and has transitioned to logged. A -4 or -5 code is now active. Repair: Service the device that is providing the desired engine speed signal, according to the literature that is provided by the OEM of the device.
8. Check the Wiring for a Short Circuit to the +Battery or Ground A. Turn the battery disconnect to the OFF position. B. Remove the wire for desired speed signal from the EIC. C. Turn the battery disconnect to the ON position. - For the 91-3 code, EIC terminal 10. - For the 29-3 code, EIC terminal 4. - For the 974-6 code, EIC terminal 59.	Short Circuit	Result: The -3 or -6 code remains active with the signal wire removed from the EIC. There is a short to a positive voltage for a -3 code or ground for a -6 code in between the engine ECM and the EIC. Repair: Repair or replace the wiring harness between the ECM and the EIC. Result: The -3 or -6 code is no longer active with the signal wire removed from the EIC. There is a short to a positive voltage for a -3 code or ground for a -6 code in between the EIC and the speed control device. Repair: Repair or replace the wiring harness between the EIC and the speed control device.
9. Create a Short Circuit A. Turn the battery disconnect switch to the OFF position. B. Remove the connector for the desired speed from the speed control device. C. Insert a jumper wire into the terminals to create a short circuit on the 4-20 mA (+) and (-). D. Turn the battery disconnect switch to the ON position. E. Observe Cat ET for a diagnostic FMI state change.	Short Circuit	Result: The -5 code remains active after the short circuit was created on the 4-20 mA (+) and (-) at the connector for the speed control device. An open circuit is present on the wiring between the ECM and the speed control device. Proceed to Test Step 10. Result: A -6 code is now active. The -5 code is no longer active and has transitioned to logged. Repair: Service the device that is providing the desired engine speed signal, according to the literature that is provided by the OEM of the device.
10. Create a Short Circuit A. Turn the battery disconnect to the OFF position. B. Remove the wires for the 4-20 mA desired speed from the OEM side of the EIC. C. Install a jumper wire into the OEM EIC terminals. D. Turn the battery disconnect switch to the ON position. 4-20 mA (+) EIC OEM side Terminal 59 4-20 mA (-) EIC OEM side Terminal 60	Short Circuit	Result: The -5 code remains active after the short circuit was created on the 4-20 mA (+) and (-) at the OEM side EIC connector. An open circuit is present on the wiring between the Engine ECM and the EIC. Repair: Repair or replace the wiring harness between the Engine ECM and EIC. Result: A -6 code is now active after the short circuit was created on the 4-20 mA (+) and (-) at the OEM side EIC connector. An open circuit is present on the wiring 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).