Usage:
General
This chapter is divided into three sections:
- * Hardware Troubleshooting
- * Software Function
- * Engine Dynamics Troubleshooting
- * Software Function
Hardware Troubleshooting
The DMMP control provides self testing and system diagnostic routines for the installed external hardware. Any hardware faults detected may be retrieved through the PC Service Tool, a fault indicator lamp, or by an SAE J1587 compatible service tool.
Once any hardware faults are determined, locate the faulted parameter(s) in the Appendix for further troubleshooting information.
NOTE: Do NOT insert probes directly into the sockets located on the mating connectors to the DMMP control. The sockets may be damaged and not make contact with the mating pins.
PC Service Tool
The active faults are displayed in the PC Service Tool under the FAULT LIST service header. A TRUE indicates that a fault has been detected and may still be present. A FALSE indicates that no fault has been detected.
A running count of the number of faults that have occurred for each hardware parameter is logged under the FAULT LOGGER service header. Currently, there will be a maximum of 5 counts for each fault parameter logged. There will be no date or time stamping involved with any of the faults logged. The logged faults may be cleared by toggling the *Clear Fault Log parameter from *FALSE to *TRUE and then back to *FALSE.
Fault Indicator
The faults detected by the DMMP are displayed on the fault lamp only if they are active or have not been reset. The control will indicate the presence of a fault by turning the fault lamp on.
The active faults are cleared by cycling the power to the DMMP control. The fault parameters indicated by the fault flash codes are listed in the Appendix.
Trigger the flash codes by quickly depressing the foot pedal twice within one-half second. The pedal must be depressed far enough to cause closure of the idle validation contact or a 5% change in position.
The DMMP control displays the fault codes by turning the fault lamp on and off. There will be a two-second delay between different codes. Each fault code is a two digit number. When displaying a fault code, the DMMP control turns the lamp on for one-half second and off for one-half second the appropriate number of times for the first digit. Then, after a one-second pause, it will similarly flash the second fault code digit.
For example, if no engine speed sensor has been detected (flash code 31), the control will flash the lamp three times, pause two seconds, then flash the lamp one time.
Repair Note
When correcting the faults, fix the first flash code first and recheck the faults. Continue this process until all of the faults are corrected.
J1587 Service Tool
Any fault codes are also retrievable on an SAE J1587 compatible service tool. A network code and a count number will be displayed on the service tool to indicate the fault type and how many times it has occurred. Currently, there will be a maximum of 5 counts of each fault parameter logged. There will be no date or time stamping involved with any of the faults logged.
The network codes retrieved correspond to the current SAE standard. The fault parameters that the codes indicate are listed in the J1587 Fault List located in the Appendix.
Refer to the J1587 service tool manual for tool connections and data retrieval instructions.
Contact Inputs
NOTE: Do NOT insert probes directly into the sockets located on the mating connectors to the DMMP control. The sockets may be damaged and not make contact with the mating pins.
The control software cannot detect external hardware faults on the contact inputs. The system functionality of these inputs should be checked as described in the Pre-Start System Checks in Chapter 6.
A problem is indicated if any of the inputs (monitored from PC Service) is not changing states from TRUE to FALSE when the corresponding switch contact is closed and opened.
Battery voltage (+) to the contact input indicates a TRUE in PC Service, while an open contact returns a FALSE.
The contact inputs are all located on DMMP connector J2 (see the DMMP wiring diagram, Figure 1-2). If this connector is removed, the voltage from each contact input pin to ground may be monitored to check the functionality of all the hardware switches. If the correct voltage is verified on the proper pins, and PC Service still indicates a problem (with the connector reinstalled), replace the control.
If the voltage to any of the contact input pins is not correct, investigate wiring or other vehicle systems that may be preventing the switch voltage from reaching the control.
ProAct Actuator
The actuator used with this Digital Min/Max control is a ProAct I.
If the actuator is moving in the wrong direction during the setup procedures, wiring errors are the most likely cause. Thoroughly check both the actuator feedback and actuator wiring and verify that they match the DMMP wiring diagram (Figure 1-2).
If the actuator is unstable, verify that the position feedback wires are properly shielded. If not, noise can be introduced into the feedback circuitry and cause problems. No additional connections should ever be made to the actuator wires.
If the actuator seems "weak" when manually moved (while powered), make sure that the gauge and length of wires used meet the specifications listed on the DMMP wiring diagram.
Actuator Feedback
If the actuator position (5% at minimum, 95% at maximum) is out of specification, the 5 volt supply to the position sensor may be at fault.
Linkage Note
The range of the actuator position readout will be directly related to the linkage and throttle body used in the application. If the actuator travel is being limited by the stops on the throttle body, the readout will be between the 5% and 95% limits.
To test, remove power from the control.
NOTE: Always remove power from the control before disconnecting or reconnecting any DMMP connector.
Disconnect the actuator connector, re-power the control, and verify that the voltage on the connector between pins B(+) and E(-) is 5.00 ± 0.20 Vdc. If the voltage is correct, replace the actuator. Otherwise replace the control.
If the position feedback voltage (monitored in PC Service) is moving in the wrong direction (increasing rotation should equal increasing voltage), the wiring to the sensor is incorrect and needs to be corrected as shown in the DMMP wiring diagram.
Control Failed Engine Starting Checks
If the DMMP did not pass the pre-start checks, check the following:
- * Verify that their are no active faults in the ACTIVE FAULT service header (except for ENGINE SPEED FAULT). If there are faults, correct them before continuing.
- * Verify the function of the contact inputs in the CONTACT INPUTS service header and set to correct state as listed in the Starting the Engine procedure in Chapter 6.
- * If the control still doesn't react as described, substitute a frequency generator in place of the engine MPU signal. Set the frequency to below 50 Hz at an amplitude of greater than 1.5 Vrms. Monitor the same service parameters as described in the Starting the Engine procedure in Chapter 6. Increase the frequency above 75 rpm (Engine RPM in PC Service) and note the control response. If the control does not react as described, replace the control.
- * Verify the function of the contact inputs in the CONTACT INPUTS service header and set to correct state as listed in the Starting the Engine procedure in Chapter 6.
Open Loop Test
With the simulated engine rpm below the idle speed reference (750 rpm) and greater than 75 rpm, the actuator should move to maximum fuel position. As the MPU frequency is increased so that the engine rpm becomes greater than the idle speed reference (750 rpm), the actuator will move to the minimum fuel position. If the door is closed and the PTO is not selected, the foot pedal can be used to move the actuator from minimum to maximum.
NOTE: Before attempting to use the foot pedal, at least one minimum foot pedal sample must be completed. This is done by setting the MPU frequency so that the engine rpm is greater than the idle speed reference but still within 5 rpm of the idle speed reference, then waiting until the actuator moves to minimum fuel position. Once the foot pedal sample is completed (actuator at minimum position), the foot pedal will control the actuator from minimum to maximum.
Next increase the MPU frequency until the simulated engine rpm is greater than the high idle speed reference. The actuator should move to minimum fuel and remain there even when the foot pedal is pressed. This procedure has tested the basic minimum governor operation, maximum governor operation, and foot pedal control. All other control functions may be tested with the control in foot pedal control.
Software Function
This section gives a brief overview of some of the fault and normal operating conditions where the DMMP will take control of (or limit) the throttle position.
NOTE: All the faults listed will also trigger a fault indication that will be retrievable through the PC Service tool, a generic J1587 service tool, or via flash code on the fault indicator lamp. See the Hardware Troubleshooting section.
Actuator to Minimum
The application software will try to force the actuator to minimum in certain critical fault modes:
- * blocked actuator fault
- * actuator position fault
- * actuator fault
- * engine overspeed
- * no MPU input signal
- * actuator position fault
Refer to the Appendix for definitions and causes for these fault conditions.
NOTE: The actuator position fault and the actuator fault will cause the actuator to go "limp," so it will return to minimum position by the return spring.
Idle Governor Control Only
The control will force engine speed to idle and disable the foot pedal input in the following conditions:
- * idle validation fault
- * sensor supply fault
- * foot pedal fault
- * idle validation contact switch open, if enabled
- * vehicle door open
- * sensor supply fault
The foot pedal will also be disabled when PTO (fast idle) speed control is enabled.
A power-down reset is necessary to clear the active faults.
Start Fuel Limiter
When engine speed is above 75 rpm, the start fuel limit causes the governor actuator to ramp open until the engine starts. The foot pedal is disabled until the engine starts. Once the engine starts, the foot pedal is enabled and the start fuel limiter ramped out of control.
Engine Dynamics Troubleshooting
Idle Speed Dynamics
The idle speed dynamics have been preset at the factory and should provide acceptable performance. Unstable engine operation may be caused by several other outside problems that may appear to be governor control problems, the most probable being governor actuator linkage setup, fuel delivery problems, or ignition problems.
With the engine not running, verify that the actuator linkage moves freely through its range and that the throttle body is not sticking in its bore.
A way to check for non-governor problems is to increase the Minimum Actuator in the ACTUATOR MONITOR service header (in Manual Calibration mode) until the engine speed is running above the Minimum Speed Reference. This fixes the actuator position and removes the speed control loop effects. Be sure to record the original settings so that they may be restored once testing is done.
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To prevent possible death, serious injury, or property damage from an engine overspeed, be prepared to shut down the engine manually while testing the DMMP dynamic response with the actuator set above the minimum stop. |
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The actuator should hold position without any movement and the engine should be stable. If the speed is drifting or oscillating excessively, try to find a source other than the governor. If the speed is stable, manually move the actuator linkage. The DMMP control should oppose any such movement and try to hold its position. If the actuator feels "weak" or unstable, refer to the ProAct Actuator section.
If the testing still points to governor a problem, you may need to adjust speed control dynamics. See the Dynamic Adjustments section below.
If speed dips unacceptably when returning to idle, the software idle stop may need to be rechecked. See Setting The Software Idle Stop in the Starting the Engine section of Chapter 6.
Maximum Speed Dynamics
The maximum speed dynamics have been set at the factory and should provide acceptable performance. When engine speed reaches the maximum speed reference, the actuator should smoothly start to close down until the engine speed is correct. If instabilities or hunting are apparent, see the Dynamic Adjustments section below.
Dynamic Adjustments
Minimum Governor Speed Dynamic Adjustments
If the default minimum speed dynamics do not provide acceptable performance, additional fine tuning may be necessary.
The available dynamic adjustments listed here are located under the MINIMUM SPEED GOVERNOR service header.
*Minimum Gain
The magnitude of the response that the control has to a speed error near the minimum speed reference.
*Minimum Stability
The rate at which the control returns the speed error to zero after a disturbance.
*Minimum Compensation
Adjusts the control for the lag time of the fuel system and actuator.
Steady State Idle Speed
If there is a slow periodic cycling of the engine speed above and below the speed reference, there are two probable causes:
Gain is too high and stability is too low. Reduce the *Minimum Gain and increase the *Minimum Stability slightly. Watch the movement of the actuator. Continue to increase *Minimum Stability until the movement is acceptable but not excessive. If the Stability value exceeds 3.0 but this continues to improve performance, increase the *Minimum Actuator Compensation by 50% and repeat the procedure.
Gain is too low. If the preceding procedure does not improve the slow periodic cycling of the engine speed, the control may be limit cycling. Increase the *Minimum Gain to minimize the cycling. If actuator movement becomes excessive, reduce the *Minimum Actuator Compensation until movement is acceptable.
Transient Response
If the speed undershoots unacceptably back to idle, or stalls, during speed transients, the minimum gain may need to be adjusted. Before changing this setpoint, first verify that the Software Idle Stop is correctly set as described under Setting the Software Idle Stop in the Starting the Engine section of Chapter 6. Also record the values so that you can restore them if necessary.
Maximum Governor Speed Dynamic Adjustments
If the default maximum speed dynamics do not provide acceptable performance, additional fine tuning may be necessary.
The available dynamic adjustments listed here are located under the MAXIMUM SPEED GOVERNOR service header.
*Maximum Gain
The magnitude of the response that the control has to a speed error while the maximum governor is in control.
*Maximum Stability
The rate at which the control returns the speed error to zero after a disturbance.
*Maximum Compensation
Adjusts the control for the lag time of the fuel system and actuator. A slower fuel system requires a larger actuator compensation.
The Maximum Speed Governor steady state and transient adjustments are the same as for the Minimum Speed Governor above.
PTO Dynamics
The PTO governor uses the minimum governor stability and actuator compensation. Optimal idle and PTO performance may have to be compromised to get acceptable performance for both governors. The PTO gain should allow enough adjustment to get optimal performance. We recommend that only the PTO gain be adjusted when tuning the PTO governor. If the stability or actuator compensation need to be changed, then the minimum governor will most likely need to be retuned.
*PTO Gain
The magnitude of the response that the control has to a speed error while the PTO governor is selected.
Once the speed has been stabilized, load the PTO device. The engine speed may change for a moment, but it should quickly return to the PTO speed. Adjust the gain as needed. The minimum governor performance should have priority over the PTO governor, so changes to the stability or actuator compensation should only be done while at the minimum governor speed.
Once the dynamic responses have been tuned for optimal performance, the vehicle is ready to run. The dynamic responses have been set for unloaded conditions. Some adjustment may be required for on-the-road loaded or in gear performance.