C7.1 Engines and Generator Sets Caterpillar

Speed Control (Analog) - Test

Usage:

C7.1 770

This procedure covers the following diagnostic codes:

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Table 1
Diagnostic Trouble Codes for Analog Throttles
J1939 Code	CDL Code	Code Description (code descriptions may vary)	Comments
91-2	91-2	Accelerator Pedal Position 1 : Erratic, Intermittent, or Incorrect	The Electronic Control Module (ECM) detects one of the following conditions: The signal from the analog throttle position sensor is invalid. If equipped, the warning lamp will come on. The diagnostic code will be logged.
29-2	774-2	Accelerator Pedal Position 2: Erratic, Intermittent, or Incorrect
91-3	91-3	Accelerator Pedal Position 1 : Voltage Above Normal	The ECM detects one of the following conditions: The ECM has been powered for 3 seconds. Diagnostic code 168-4 is not active. 3509 codes are not active. The setting for the upper diagnostic limit has been exceeded for one second. If equipped, the warning lamp will come on. The diagnostic code will be logged.
29-3	774-3	Accelerator Pedal Position 2: Voltage Above Normal
91-4	91-4	Accelerator Pedal Position 1 : Voltage Below Normal	The ECM detects one of the following conditions: The ECM has been powered for 3 seconds. Diagnostic code 168-4 is not active. 3510 codes are not active. The setting for the lower diagnostic limit has been exceeded for one second. If equipped, the warning lamp will come on. The diagnostic code will be logged.
29-4	774-4	Accelerator Pedal Position 2: Voltage Below Normal

If a fault occurs with the primary throttle with secondary throttle is installed, the secondary throttle will be used until the fault is repaired.

If a fault occurs with the secondary throttle, the engine will use the primary throttle until the fault is repaired.

If a functional throttle is not available, the following conditions will occur:

The engine will default to the limp home speed.
If the engine speed is higher than the limp home speed, the engine will decelerate to the limp home speed.
If the engine speed is lower than the limp home speed, the engine speed will remain at the current speed.
The engine will remain at this speed while the diagnostic code remains active.
All inputs from the faulty throttle are ignored by the ECM until the fault is repaired.
All inputs from the repaired throttle will be ignored by the ECM until the keyswitch has been cycled.

The diagnostic codes above relate to an analog sensor. Use this procedure only if the analog sensor uses an output from a variable resistor.

The sensor is most likely to be mounted on a throttle pedal. The sensor is attached directly to the throttle assembly. The sensor provides an output voltage to the ECM. The sensor output voltage will vary with the position of the throttle. Foot operated or hand operated throttle assemblies are available.

The sensor receives +5 VDC power from the ECM. The sensor will produce a raw signal voltage that will alter between low idle and high idle. The voltage is changed into a throttle position within the range 0% to 100% by the ECM.

The sensor senses the speed requirement from the throttle position. A second sensor may override this speed requirement from the first sensor. This override will be subject to an input from a secondary throttle or from the SAE J1939 (CAN) data link or from a PTO control.

Use the electronic service tool to check the input status.

Note: The identification letters for the terminals in the connectors may vary dependent on the manufacturer of the throttle pedal.

During the following procedure, refer to the electrical schematic for the application.

Complete the procedure in the order in which the steps are listed.

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Table 2
Troubleshooting Test Steps	Values	Results
1. Inspect Electrical Connectors and Wiring A. Thoroughly inspect the terminal connections on the P1/J1 ECM connector and the analog throttle position sensors. Refer to Troubleshooting, "Electrical Connector - Inspect". B. Perform a 45 N (10 lb) pull test on each of the wires in the ECM connector and the analog throttle position sensor connectors that are associated with the active diagnostic code. C. Check the screw for the ECM connector for the correct torque of 6 N·m (53 lb in). D. Check the harness for corrosion, abrasion, and pinch points from the analog throttle position sensors to the ECM.	Loose connection or damaged wire	Result: There is a fault in a connector or the wiring. Repair: Repair any faulty connectors or replace the wiring harness. Ensure that all the seals are properly in place and ensure that the connectors are correctly coupled. Use the electronic service tool to clear all logged diagnostic codes and verify that the repair eliminates the fault. Result: All connectors, pins, and sockets are correctly coupled and/or inserted. The harness is free of corrosion, abrasion, and pinch points. Proceed to Test Step 2.
2. Check for Active Diagnostic Codes A. Turn the keyswitch to the OFF position. B. Connect the electronic service tool to the diagnostic connector. C. Turn the keyswitch to the ON position. Wait at least 10 seconds for activation of the diagnostic codes. D. Verify if any of the diagnostic codes that are listed in Table 1 are active. E. Turn the keyswitch to the OFF position.	Diagnostic codes	Result: There are no active diagnostic codes for the analog throttle position sensors. Proceed to Test Step 3. Result: One or more of the diagnostic codes listed in Table 1 is active. Proceed to Test Step 5.
3. Check the Throttle Position with the Electronic Service Tool A. Connect the electronic service tool to the diagnostic connector. B. Turn the keyswitch to the ON position. Do not start the engine. C. Observe the throttle position reading on the electronic service tool. D. Operate the throttle over the full range of movement.	20 percent to 27 percent at low idle. 80 percent to 87 percent at high idle	Result: The ECM is not receiving the correct signal from the sensor. Repair: Use the electronic service tool to verify that the throttle has been configured correctly before continuing with this procedure. If the fault is still present after the throttle has been configured correctly, replace the analog throttle position sensor. Result: The sensor is operating correctly. Proceed to Test Step 4.
4. Check the Throttle Selection Status with the Electronic Service Tool A. Check the status of the throttle selection switch (if equipped). Use the electronic service tool to check the status of the throttle selection switch.	Throttle 1 has control when status is "OFF". Throttle 2 has control when status is ON.	Result: The throttle section switch is operating correctly. Return the engine to service. If an intermittent fault exists, refer to Troubleshooting, "Electrical Connector - Inspect" Result: The wrong throttle is selected. Repair: Switch to the other throttle. There may be a fault with the selector switch input. Check the connections between the throttle selection switch and the P1 connector. Refer to Troubleshooting, "Electrical Connector - Inspect".
5. Check the Sensor Supply Voltage A. Turn the keyswitch to the OFF position. B. Disconnect the connector for the suspect throttle position sensor. C. Turn the keyswitch to the ON position. D. Measure the voltage between the 5 VDC terminal and the ground terminal on the harness connector for the sensor.	4.84 VDC to 5.16 VDC	Result: The correct supply voltage is not reaching the sensor. The fault is in the 5 VDC supply wire or the ground wire between the suspect throttle position sensor and the P1 connector. Repair: Repair the faulty wiring or replace the faulty wiring. Use the electronic service tool to clear all logged diagnostic codes and verify that the repair eliminates the fault. Result: The supply voltage is reaching the sensor. Proceed to Test Step 6.
6. Verify the Type of Active Diagnostic Code A. Turn the keyswitch to the ON position. Wait at least 10 seconds for activation of the diagnostic codes. B. Use the electronic service tool to check for active diagnostic codes. Record all active diagnostic codes.	Diagnostic codes	Result: A 29-3, 774-3, or 91-3 diagnostic code is active. Proceed to Test Step 7. Result: A 29-4, 774-4, or 91-4 diagnostic code is active. Proceed to Test Step 9. Result: There are no active diagnostic codes for the throttle position sensors - The fault may be intermittent. Repair: Refer to Troubleshooting, "Electrical Connector - Inspect".
7. Create a Short Circuit at the Sensor Connector A. Turn the keyswitch to the OFF position. B. Disconnect the throttle position sensor with the XX-3 diagnostic code. C. Fabricate a jumper wire. Install the jumper wire between the sensor signal terminal and the ground terminal on the harness connector for the throttle position sensor. D. Turn the keyswitch to the ON position. E. Access the "Active Diagnostic Codes" screen on the electronic service tool. Look for an active XX-4 diagnostic code for the suspect sensor. F. Turn the keyswitch to the OFF position. G. Remove the jumper wire.	Diagnostic codes	Result: An XX-3 diagnostic code was active before the jumper was installed. An XX-4 diagnostic code is active with the jumper installed. Repair: Install a replacement analog throttle position sensor. Use the electronic service tool to clear all logged diagnostic codes and verify that the repair eliminates the fault. Result: The XX-3 diagnostic code remains active with the jumper installed. Proceed to Test Step 8.
8. Check the Sensor Signal Wire for an Open Circuit A. Turn the keyswitch to the OFF position. B. Disconnect the suspect throttle position sensor. Disconnect the P1 connector from the ECM. C. Measure the resistance between the sensor signal terminal on the harness connector and the appropriate sensor signal terminal on the P1 connector.	Less than 2.0 Ohms	Result: The resistance measurement is greater than 2.0 Ohms - There is an open circuit or high resistance in the sensor signal wire. Repair: Repair the faulty wiring or replace the faulty wiring. Use the electronic service tool to clear all logged diagnostic codes and verify that the repair eliminates the fault. Result: The resistance measurement is less than 2.0 Ohms. Contact the Dealer Solutions Network (DSN).
9. Create an Open Circuit at the Sensor Connector A. Turn the keyswitch to the OFF position. B. Disconnect the throttle position sensor with the XX-4 diagnostic code. C. Turn the keyswitch to the ON position. Wait for at least 10 seconds for activation of the diagnostic codes. D. Use the electronic service tool to check the "Active Diagnostic Codes" screen on the electronic service tool. Check for an XX-3 diagnostic code. E. Turn the keyswitch to the OFF position.	Diagnostic codes	Result: An XX-4 diagnostic code was active before disconnecting the sensor. An XX-3 diagnostic code is active with the sensor disconnected. Repair: Install a replacement analog throttle position sensor. Use the electronic service tool to clear all logged diagnostic codes and verify that the repair eliminates the fault. Result: The XX-4 diagnostic code is still active with the sensor disconnected. Proceed to Test Step 10.
10. Check the Sensor Signal Wire for a Short Circuit A. Turn the keyswitch to the OFF position. B. Disconnect the suspect throttle position sensor. Disconnect the P1 connector from the ECM. C. Measure the resistance between the suspect sensor signal terminal and all other terminals on the P1 connector.	Greater than 100 Ohms	Result: At least one of the resistance measurements is less than 100 Ohms - There is a short in the wiring harness. Repair: Repair the faulty wiring or replace the faulty wiring. Result: All resistance measurements are greater than 100 Ohms. Contact the Dealer Solutions Network (DSN).