Paccar

PACCAR MX (2004 Emissions) Fault Code: U177B Accelerator Pedal 1 – Voltage Too High or Short Circuit to Supply on ECU (D420) Pin (B41)

SET CONDITIONS:
This DTC is set when the ECU detects a higher voltage than expected on the signal or control circuit of the ECU.

DIAGNOSTIC CONDITION:
The diagnostic runs continuously when the ignition is keyed on.

CORRESPONDING OBD READINESS MONITOR:
None

RESET CONDITION:
The DTC changes to inactive after the diagnostic runs and passes.

REPAIR VERIFICATION:
1. Clear all DTCs.
2. Test drive or operate the vehicle to meet the diagnostic conditions and set conditions.
3. Did the DTC come back?
– No, repair successful
– Yes, repair unsuccessful

POSSIBLE CAUSES:
1. The sensor or actuator signal wiring has a short circuit to supply.
2. A malfunction of the sensor or actuator

PACCAR MX (2004 Emissions) Fault Code: U177C Accelerator Pedal 1 – Voltage Too Low or Short Circuit to Ground on ECU (D420) Pin (B41)

SET CONDITIONS:
This DTC is set when the ECU detects a lower voltage than expected on the signal or control circuit of the ECU.

DIAGNOSTIC CONDITION:
The diagnostic runs continuously when the ignition is keyed on.

CORRESPONDING OBD READINESS MONITOR:
None

RESET CONDITION:
The DTC changes to inactive after the diagnostic runs and passes.

REPAIR VERIFICATION:
1. Clear all DTCs.
2. Test drive or operate the vehicle to meet the diagnostic conditions and set conditions.
3. Did the DTC come back?
– No, repair successful
– Yes, repair unsuccessful

POSSIBLE CAUSES:
1. The sensor or actuator signal wiring is interrupted.
2. The sensor or actuator signal wiring has a short circuit to ground.
3. A malfunction in the power supply of the sensor or actuator
4. A malfunction of the sensor or actuator

ADDITIONAL INFORMATION:
Multiple sensor related voltage-too-low DTCs can indicate a malfunction within a 5-V sensor power supply circuit of the PCI ECU.

PACCAR MX (2004 Emissions) Fault Code: U177D Accelerator Pedal Sensor 1 Duty Cycle – Data Valid but Too High on ECU (D420) Pin (B41)

SET CONDITIONS:
The PCI ECU (D420) detects that the duty cycle of accelerator pedal position sensor 1 is higher than expected.

DIAGNOSTIC CONDITION:
This diagnostic runs continuously when the ignition is on.

CORRESPONDING OBD READINESS MONITOR:
None

RESET CONDITION:
This DTC changes to inactive when the fault is no longer detected. To validate the repair, monitor the accelerator pedal sensors with the diagnostic service tool.

REPAIR VERIFICATION:
1. Clear all DTCs.
2. Test drive or operate the vehicle to meet the diagnostic conditions and set conditions.
3. Did the DTC come back?
– No, repair successful
– Yes, repair unsuccessful

POSSIBLE CAUSES:
Faulty accelerator pedal or wiring

ADDITIONAL INFORMATION:
The accelerator pedal position is determined by two sensors (1 and 2) inside the accelerator pedal. The sensor outputs are PWM signals at a fixed frequency of 180 to 220 Hz. Sensor signals 1 and 2 are reversed compared to each other, meaning that by pressing the accelerator more, sensor 1 shows a decreasing PWM signal and sensor 2 shows an increasing PWM signal. The PCI ECU monitors both sensors separately and together.

PACCAR MX (2004 Emissions) Fault Code: U177E Accelerator Pedal Sensor 1 Duty Cycle – Data Valid but Too Low on ECU (D420) Pin (B41)

SET CONDITIONS:
The PCI ECU (D420) detects that the duty cycle of accelerator pedal position sensor 1 is lower than expected.

DIAGNOSTIC CONDITION:
This diagnostic runs continuously when the ignition is on.

CORRESPONDING OBD READINESS MONITOR:
None

RESET CONDITION:
This DTC changes to inactive when the fault is no longer detected. To validate the repair, monitor the accelerator pedal sensors with the diagnostic service tool.

REPAIR VERIFICATION:
1. Clear all DTCs.
2. Test drive or operate the vehicle to meet the diagnostic conditions and set conditions.
3. Did the DTC come back?
– No, repair successful
– Yes, repair unsuccessful

POSSIBLE CAUSES:
Faulty accelerator pedal or wiring

ADDITIONAL INFORMATION:
The accelerator pedal position is determined by two sensors (1 and 2) inside the accelerator pedal. The sensor outputs are PWM signals at a fixed frequency of 180 to 220 Hz. Sensor signals 1 and 2 are reversed compared to each other, meaning that by pressing the accelerator more, sensor 1 shows a decreasing PWM signal and sensor 2 shows an increasing PWM signal. The PCI ECU monitors both sensors separately and together.

PACCAR MX (2004 Emissions) Fault Code: U177F Accelerator Pedal 1 Frequency – Data Valid but Too High on ECU (D420) Pin (B41)

SET CONDITIONS:
The PCI ECU (D420) detects that the frequency of accelerator pedal position sensor 1 is more than 220 Hz.

DIAGNOSTIC CONDITION:
This diagnostic runs continuously when the ignition is on.

CORRESPONDING OBD READINESS MONITOR:
None

RESET CONDITION:
This DTC changes to inactive when the fault is no longer detected. To validate the repair, monitor the accelerator pedal sensors with the diagnostic service tool.

REPAIR VERIFICATION:
1. Clear all DTCs.
2. Test drive or operate the vehicle to meet the diagnostic conditions and set conditions.
3. Did the DTC come back?
– No, repair successful
– Yes, repair unsuccessful

POSSIBLE CAUSES:
Faulty accelerator pedal or wiring

ADDITIONAL INFORMATION:
The accelerator pedal position is determined by two sensors (1 and 2) inside the accelerator pedal. The sensor outputs are PWM signals at a fixed frequency of 180 to 220 Hz. Sensor signals 1 and 2 are reversed compared to each other, meaning that by pressing the accelerator more, sensor 1 shows a decreasing PWM signal and sensor 2 shows an increasing PWM signal. The PCI ECU monitors both sensors separately and together.

PACCAR MX (2004 Emissions) Fault Code: U1789 CAN Communication – Message (PROBA_BBM_to_Eng) Out of Range, Starter Interrupt from Body Builder Module

SET CONDITIONS:
This DTC is set when a CAN message is received correctly, but the content (signal value or status) is out of the expected range.

DIAGNOSTIC CONDITION:
The diagnostic runs continuously when the ignition is keyed on or when the engine is running.

CORRESPONDING OBD READINESS MONITOR:
None

RESET CONDITION:
The DTC changes to inactive after the diagnostic runs and passes.

REPAIR VERIFICATION:
1. Clear all DTCs.
2. Test drive or operate the vehicle to meet the diagnostic conditions and set conditions.
3. Did the DTC come back?
– No, repair successful
– Yes, repair unsuccessful

POSSIBLE CAUSES:
1. A corrupt or empty CAN message
2. A malfunction in the system from which the message originates

ADDITIONAL INFORMATION:
1. A ‘message out of range’ DTC is activated by the receiving ECU but indicates a malfunction within another system which communicates with this ECU.
2. The cause of the DTC must be sought in the system from which it originates.

Example:
1. [ECU 1] detects an incorrect or missing signal from [sensor A].
2. [ECU 1] sets [DTC 1] (In this specific case, an open circuit DTC).
3. [ECU 1] constantly informs [ECU 2] about the status of [sensor A] via CAN messages.
4. Since the data received from the sensor is not available or not plausible, an ’empty’ CAN message is sent from [ECU 1] to [ECU 2].
5. [ECU 2] interprets the empty message as being out of the expected range and sets the ‘out of range DTC’ [DTC 2].