C-10, C-12, 3406E, C-15, C-16 and C-18 Engines - Electronic PTO Installation and Application Caterpillar


Remote PTO Accelerator Position Sensor Circuit - Test

Usage:

3406E 1MM
System Operation Description:

Use this procedure under the following situation:

Use this procedure if any of the following diagnostic codes are indicated:

  • 30-08 Invalid PTO Throttle Signal (29)

  • 30-13 PTO Throttle Sensor Calibration (29)

Also, use this procedure if the remote accelerator position sensor is suspected of improper operation.

Remote Accelerator Position Sensor

A remote accelerator position sensor may be used for PTO purposes. The remote accelerator position sensor should be connected to the ECM connector J1/P1:68. Before the ECM will respond to the remote accelerator position sensor, the ECM PTO Configuration must be programmed to Remote Throttle, and the PTO On/Off Switch must be in the ON position. Also, Caterpillar offers the following recommendation:

  • The remote accelerator position sensor must be powered from the vehicle battery (+12 V).

Therefore, the +12 V version of the accelerator position sensor must be used for the remote accelerator position sensor, and the +8 V version for the accelerator pedal position sensor in the cab.

The ECM will not respond to the remote accelerator position sensor if 253-02 Check Customer or System Parameters (56) is active under some conditions. Refer to Troubleshooting, "ECM Memory - Test" if 253-02 Check Customer or System Parameters (56) is active.

The remote accelerator position sensor is used to provide a throttle position signal to the ECM. Sensor output is a constant frequency signal with a pulse width that varies with the pedal position. This output signal is referred to as either a duty cycle or a pulse width modulated signal (PWM) and this output signal is expressed as a percentage between 3 and 100 percent.

The accelerator position sensor in the cab is attached directly to the accelerator pedal assembly and the sensor requires no adjustment.

The accelerator position sensor will produce a duty cycle of 10 to 22 percent at low idle and 75 to 90 percent when the accelerator pedal is fully depressed. The percent of duty cycle is translated in the ECM into an accelerator pedal position of 3 to 100 percent.

The accelerator position sensor can be replaced separately from the pedal assembly. An incorrectly calibrated pedal assembly can not be adjusted. The entire pedal assembly must be replaced.

If the vehicle is using the ECM dedicated PTO functions, the accelerator position sensor will be ignored while the engine is in PTO mode and the PTO Configuration is programmed to the following setting:

  • Remote Throttle

The ECM is in PTO mode if the PTO On/Off Switch is on. This can be checked through the status screen on ET.

The ECM will not respond to the remote accelerator position sensor when both of the following conditions are met:

  • The PTO On/Off circuit is switched from the OFF position to the ON position.

  • The ECM reads the remote accelerator position sensor above low idle.

This prevents the engine from experiencing unexpected acceleration or sudden acceleration when the PTO On/Off circuit is turned on. The remote accelerator position sensor must return to low idle before the ECM will respond. The ECM must also see a transition from the OFF position to the ON position in the PTO On/Off Switch in order to allow the other PTO speed control functions to operate. If the engine is started with the PTO On/Off Switch in the ON position, the accelerator will respond. The response will occur only if the accelerator pedal is first returned to the low idle position. The other speed control functions will not respond.




Illustration 1g00642017

Schematic for remote accelerator pedal position sensor




Illustration 2g00642018

Terminal locations for ECM

Test Step 1. Inspect Electrical Connectors and Wiring

  1. Connect ET to the cab data link connector. Verify that the parameter for the PTO Configuration is programmed to the "Remote Throttle".

  1. Thoroughly inspect ECM vehicle harness connector J1/P1, the firewall bulkhead connector and the connector for the remote accelerator position sensor. Refer to Troubleshooting, "Electrical Connectors - Inspect" for details.

  1. Perform a 45 N (10 lb) pull test on each of the wires in the ECM connector that are associated with the remote accelerator position sensor:

    • J1/P1:68

  1. Check the ECM connector (Allen Head Screw) for the proper torque of 6.0 N·m (55 lb in).

  1. Check the harness and wiring for abrasion and pinch points from the remote accelerator position sensor to the ECM.

Expected Result:

All connectors, pins and sockets should be completely coupled and/or inserted and the harness and wiring should be free of corrosion, abrasion or pinch points.

Results:

  • OK - Proceed to Test Step 2.

  • Not OK -

    Repair: Perform the following diagnostic procedure:Repair the connectors or wiring and/or replace the connectors or wiring. Ensure that all of the seals are properly in place and ensure that the connectors are completely coupled.Verify that the repair eliminates the problem.

    Stop.

Test Step 2. Check for Active Diagnostic Codes

  1. Connect ET to the cab data link connector.

  1. Turn the ignition key switch to the ON position.

  1. Monitor the active diagnostic code screen on ET. Check and record active diagnostic codes.

    Note: When the ECM automatically calibrates new duty cycle values for the low idle throttle position and the high idle throttle position the ECM assumes 22 percent duty cycle at low idle and 75 percent duty cycle at high idle. As a result, you may notice that the PTO throttle position status reaches 100 percent well before the remote PTO accelerator pedal is fully depressed. This is normal. After some cycling of the accelerator pedal to the high idle position, the ECM will adjust the calibration automatically. The ECM will adjust the calibration automatically provided that the high idle stop position is within the 75 to 90 percent duty cycle range, and the low idle is in the 10 to 22 percent duty cycle range. During normal operation, you may notice that more movement of the remote PTO accelerator pedal is required for the PTO throttle position status to increase above 3 percent. You may also observe that the status reaches the 100 percent value prior to the limit of the high idle position. This is done in order to ensure that the accelerator reaches these two critical points for engine operation.

Expected Result:

Result 1 Diagnostic Code 30-08 or 30-13 is active.

Result 2 There are no active diagnostic codes that are related to the accelerator position sensor circuit at this time, but a problem is suspected with operation of the remote PTO acelerator position sensor circuit.

Results:

  • Result 1 - Proceed to Test Step 3.

  • Result 2 - Proceed to Test Step 3.

Test Step 3. Check the Supply Voltage for the Remote Accelerator Position Sensor

  1. Turn the ignition key switch to the ON position.

  1. Measure the voltage at terminal "A" (+12 V) with reference to terminal "B" (sensor common) at the connector J406. This connector is for the remote accelerator position sensor.

Expected Result:

The measured voltage is between 11.0 VDC and 13.5 VDC.

Results:

  • OK - The voltage is OK. Proceed to Test Step 4.

  • Not OK - The vehicle wiring or the battery is causing the problem. Repair the wiring or the battery. Replace the wiring or the battery. Perform the repair that is necessary. Verify that the repair has fixed the problem. Stop.

Test Step 4. Check the Duty Cycle of the Remote Accelerator Pedal Position Sensor

  1. Turn the ignition key switch to the ON position.

  1. Monitor the duty cycle of the PTO throttle sensor on ET. Access the following display screen in order:

    • "Service"

    • "Calibrations"

    • "Monitor Throttle Position Sensor"

Expected Result:

The duty cycle is between 10 and 22 percent with the accelerator pedal assembly in the low idle position, and the duty cycle is between 75 and 90 percent with the accelerator pedal assembly in the high idle position.

Results:

  • OK - The remote accelerator position sensor is operating correctly. Proceed to Test Step 5.

  • Not OK - The remote accelerator position sensor circuit is not operating correctly. Proceed to Test Step 6.

Test Step 5. Check the Status of the Power Train Data Link on ET

  1. Start the engine. While the status of the PTO throttle position is being monitored on ET, depress the remote PTO accelerator pedal and release the remote PTO accelerator pedal. The throttle position status and the engine should respond to the change in the accelerator pedal position.

  1. Go to the "System Troubleshooting Settings" portion of ET and turn off the power train data link.

  1. While the status of the PTO throttle position is being monitored on ET, depress the accelerator pedal and release the accelerator pedal. Also depress the accelerator pedal and release the accelerator pedal while the engine response is being monitored.

Expected Result:

The status of the PTO throttle position and the engine should respond to the change in the accelerator pedal position.

Result 1 The PTO accelerator is functioning properly.

Result 2 The throttle response is limited by a power train data link message.

Results:

  • Result 1 - The remote accelerator position sensor is operating correctly. Continue troubleshooting until the original condition is resolved. Stop.

  • Result 2 - If the engine responds with the power train data link in the OFF position, but not with the power train data link in the ON position, a component of the power train data link is causing the response problem of the remote accelerator position sensor. Send the truck to the vehicle manufacturer in order to repair the faulty component of the power train data link. Stop.

Test Step 6. Check the Duty Cycle of the Remote Accelerator Position Sensor at the Sensor

Note: Performing certain steps within this procedure requires the use of a multimeter that is capable of measuring a PWM duty cycle.

  1. Turn the ignition key switch to the OFF position.

  1. Remove the signal wire for the remote accelerator position sensor (terminal "C") from J406. This is the vehicle harness side of the connector for the accelerator position sensor.

  1. Install a breakout T with 3 terminals at the connector J406/P406 for the remote accelerator position sensor.

  1. Connect the multimeter probes to terminal "C" (Accelerator Pedal Position) and terminal "B" (Accelerator/Switch Sensor Common) of the breakout T.

  1. While the duty cycle is being monitored on the multimeter, depress the accelerator pedal and release the accelerator pedal.

Expected Result:

The duty cycle is between 10 and 22 percent with the accelerator pedal assembly in the low idle position, and the duty cycle is between 75 and 90 percent with the accelerator pedal assembly in the high idle position.

Results:

  • OK - Reinsert the wire (terminal "C") into the connector for the remote accelerator position sensor. The sensor is working correctly. Proceed to Test Step 7.

  • Not OK - Leave the PWM probe connected to the breakout T. Insert the wire (terminal "C") into the connector for the remote accelerator position sensor. The sensor or the accelerator pedal assembly is faulty. Proceed to Test Step 8.

Test Step 7. Check the Duty Cycle of the Remote Accelerator Position Sensor at the ECM

Note: Performing certain steps within this procedure requires the use of a multimeter that is capable of measuring a PWM duty cycle.

  1. Turn the ignition key switch to the OFF position.

  1. Remove the wire from P1:68 (Remote Accelerator Position Sensor) from ECM connector P1/J1.

  1. Connect the multimeter probes between the removed wire and the ECM sensor common or ground.

  1. Turn the ignition key switch to the ON position.

  1. Use the multimeter in order to display the duty cycle output of the accelerator position sensor. While the duty cycle output of the remote accelerator position sensor is being monitored on the multimeter, move the accelerator assembly from the low idle position to the high idle position. Record the results.

  1. Turn the ignition key switch to the OFF position.

  1. Insert terminal 68 into the ECM vehicle connector P1/J1 (70 Terminal).

Expected Result:

The duty cycle is between 10 and 22 percent with the accelerator pedal assembly in the low idle position, and the duty cycle is between 75 and 90 percent with the accelerator pedal assembly in the high idle position.

Results:

  • OK - A good signal from the remote accelerator position sensor is reaching the ECM. Verify that the ECM is receiving the proper battery voltage. If the ECM is receiving the proper battery voltage, temporarily connect a test ECM and verify that the problem is resolved. If the problem disappears with the test ECM, reconnect the suspect ECM. If the problem returns with the suspect ECM, replace the ECM. Stop.

  • Not OK - There is a problem with signal wire for the remote accelerator position sensor in the vehicle wiring harness. Proceed to Test Step 9.

Test Step 8. Remove the Remote Accelerator Position Sensor From the Accelerator Pedal Assembly

  1. Turn the ignition key switch to the OFF position.

  1. Remove the remote accelerator position sensor from the accelerator pedal assembly. Note sensor orientation in the accelerator pedal assembly, and the sensor pigtail routing prior to sensor removal. Thoroughly inspect the pigtail for signs of abrasion.

  1. Connect the multimeter that is capable of measuring a PWM duty cycle to terminal "C" of the breakout T.

  1. Turn the ignition key switch to the ON position.

  1. Display the duty cycle output of the remote accelerator position sensor while the sensor slot is released. Use a screwdriver to advance the sensor slot to the maximum position. Refer to Illustration 3.

    When the sensor is removed from the accelerator pedal assembly the following diagnostic codes may be generated:

    • 30-13 PTO Throttle Sensor Calibration (29)

    The diagnostic code should disappear when the sensor is properly assembled back into the accelerator pedal assembly.




Illustration 3g00642019

(1) Mounting screw holes

(2) Sensor slot

(3) Sensor housing

(4) Mounting surface for sensor

(5) Accelerator pedal assembly

(6) Accelerator block assembly

Expected Result:

When the sensor is removed from the accelerator pedal assembly and the sensor slot is released, the duty cycle is 10 percent or less. When the sensor slot is moved to the maximum position, the duty cycle increases to 90 percent or more.

Results:

  • OK - The remote accelerator position sensor is working correctly. Clear any diagnostic codes that were caused by performing this test procedure. Refer to the OEM dealer for correct replacement of the accelerator pedal assembly. Stop.

  • Not OK - The remote accelerator position sensor is faulty. Check the accelerator pedal assembly in order to ensure that the accelerator pedal assembly is not causing damage to the sensor. If the accelerator pedal assembly is causing damage to the sensor, refer to the OEM dealer for correct replacement of the accelerator pedal assembly. Stop.

Test Step 9. Route the Supply Bypass Wires to the Remote Accelerator Pedal Position Sensor

  1. Turn the ignition key switch to the OFF position.

  1. Remove P1:66 remote accelerator position sensor from the ECM connector P1.

  1. Remove terminal "C" (Accelerator Pedal Position) from the connector for the remote accelerator position sensor.

  1. Route new wiring from the ECM to the remote accelerator position sensor.

  1. Turn the ignition key switch to the ON position.

  1. Check the duty cycle of the remote accelerator position sensor with ET while the accelerator pedal assembly is being moved over the full range.

Expected Result:

The duty cycle is between 10 and 22 percent with the accelerator pedal assembly in the low idle position, and the duty cycle is between 75 and 90 percent with the accelerator pedal assembly in the high idle position.

Results:

  • OK - The wiring from the ECM to the accelerator position sensor appears faulty. Permanently install new wiring. Verify that the repair eliminates the problem. Stop.

  • Not OK - Double check the wiring, the ECM vehicle harness connector J1/P1 and the sensor connector. If a problem still exists, restart the test procedure. Stop.
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