Paccar

PACCAR MX (2004 Emissions) Fault Code: P1266 Cylinder 2 – Torque Contribution Too High

SET CONDITIONS:
The PCI ECU (D420) detects that the combustion contribution of cylinder 2 is higher relative to the other cylinders.

DIAGNOSTIC CONDITION:
This diagnostic runs when the engine is running at a steady speed and load, and the vehicle speed is steady.

CORRESPONDING OBD READINESS MONITOR:
Fuel system monitor

RESET CONDITION:
This DTC changes to inactive when the fault is no longer detected.

REPAIR VERIFICATION:
1. Clear all DTCs.
2. Test drive or operate the vehicle to meet the following conditions:
– Corresponding readiness monitor displays ‘Ready’
– Diagnostic conditions are met
– Set conditions are met
3. Did the DTC come back? (Can be pending, inactive or active)
– No, repair successful
– Yes, repair unsuccessful

POSSIBLE CAUSES:
Fault cylinder 2 injector (overfueling)

ADDITIONAL INFORMATION:
The PCI ECU is able to detect and identify several modes of combustion failure based upon analysis of the rotational speed of the engine. The results from the cylinder-to-cylinder engine speed and the measured combustion-induced rotational acceleration are compared against a stored value which is regularly updated when no faults are present. In this way, the cylinder contribution for each cylinder can be determined.

PACCAR MX (2004 Emissions) Fault Code: P1269 Cylinder 3 – Torque Contribution Too High

SET CONDITIONS:
The PCI ECU (D420) detects that the combustion contribution of cylinder 3 is higher relative to the other cylinders.

DIAGNOSTIC CONDITION:
This diagnostic runs when the engine is running at a steady speed and load, and the vehicle speed is steady.

CORRESPONDING OBD READINESS MONITOR:
Fuel system monitor

RESET CONDITION:
This DTC changes to inactive when the fault is no longer detected.

REPAIR VERIFICATION:
1. Clear all DTCs.
2. Test drive or operate the vehicle to meet the following conditions:
– Corresponding readiness monitor displays ‘Ready’
– Diagnostic conditions are met
– Set conditions are met
3. Did the DTC come back? (Can be pending, inactive or active)
– No, repair successful
– Yes, repair unsuccessful

POSSIBLE CAUSES:
Fault cylinder 3 injector (overfueling)

ADDITIONAL INFORMATION:
The PCI ECU is able to detect and identify several modes of combustion failure based upon analysis of the rotational speed of the engine. The results from the cylinder-to-cylinder engine speed and the measured combustion-induced rotational acceleration are compared against a stored value which is regularly updated when no faults are present. In this way, the cylinder contribution for each cylinder can be determined.

PACCAR MX (2004 Emissions) Fault Code: P1272 Cylinder 4 – Torque Contribution Too High

SET CONDITIONS:
The PCI ECU (D420) detects that the combustion contribution of cylinder 4 is higher relative to the other cylinders.

DIAGNOSTIC CONDITION:
This diagnostic runs when the engine is running at a steady speed and load, and the vehicle speed is steady.

CORRESPONDING OBD READINESS MONITOR:
Fuel system monitor

RESET CONDITION:
This DTC changes to inactive when the fault is no longer detected.

REPAIR VERIFICATION:
1. Clear all DTCs.
2. Test drive or operate the vehicle to meet the following conditions:
– Corresponding readiness monitor displays ‘Ready’
– Diagnostic conditions are met
– Set conditions are met
3. Did the DTC come back? (Can be pending, inactive or active)
– No, repair successful
– Yes, repair unsuccessful

POSSIBLE CAUSES:
Fault cylinder 4 injector (overfueling)

ADDITIONAL INFORMATION:
The PCI ECU is able to detect and identify several modes of combustion failure based upon analysis of the rotational speed of the engine. The results from the cylinder-to-cylinder engine speed and the measured combustion-induced rotational acceleration are compared against a stored value which is regularly updated when no faults are present. In this way, the cylinder contribution for each cylinder can be determined.

PACCAR MX (2004 Emissions) Fault Code: P1275 Cylinder 5 – Torque Contribution Too High

SET CONDITIONS:
The PCI ECU (D420) detects that the combustion contribution of cylinder 5 is higher relative to the other cylinders.

DIAGNOSTIC CONDITION:
This diagnostic runs when the engine is running at a steady speed and load, and the vehicle speed is steady.

CORRESPONDING OBD READINESS MONITOR:
Fuel system monitor

RESET CONDITION:
This DTC changes to inactive when the fault is no longer detected.

REPAIR VERIFICATION:
1. Clear all DTCs.
2. Test drive or operate the vehicle to meet the following conditions:
– Corresponding readiness monitor displays ‘Ready’
– Diagnostic conditions are met
– Set conditions are met
3. Did the DTC come back? (Can be pending, inactive or active)
– No, repair successful
– Yes, repair unsuccessful

POSSIBLE CAUSES:
Fault cylinder 5 injector (overfueling)

ADDITIONAL INFORMATION:
The PCI ECU is able to detect and identify several modes of combustion failure based upon analysis of the rotational speed of the engine. The results from the cylinder-to-cylinder engine speed and the measured combustion-induced rotational acceleration are compared against a stored value which is regularly updated when no faults are present. In this way, the cylinder contribution for each cylinder can be determined.

PACCAR MX (2004 Emissions) Fault Code: P1278 Cylinder 6 – Torque Contribution Too High

SET CONDITIONS:
The PCI ECU (D420) detects that the combustion contribution of cylinder 6 is higher relative to the other cylinders.

DIAGNOSTIC CONDITION:
This diagnostic runs when the engine is running at a steady speed and load, and the vehicle speed is steady.

CORRESPONDING OBD READINESS MONITOR:
Fuel system monitor

RESET CONDITION:
This DTC changes to inactive when the fault is no longer detected.

REPAIR VERIFICATION:
1. Clear all DTCs.
2. Test drive or operate the vehicle to meet the following conditions:
– Corresponding readiness monitor displays ‘Ready’
– Diagnostic conditions are met
– Set conditions are met
3. Did the DTC come back? (Can be pending, inactive or active)
– No, repair successful
– Yes, repair unsuccessful

POSSIBLE CAUSES:
Fault cylinder 6 injector (overfueling)

ADDITIONAL INFORMATION:
The PCI ECU is able to detect and identify several modes of combustion failure based upon analysis of the rotational speed of the engine. The results from the cylinder-to-cylinder engine speed and the measured combustion-induced rotational acceleration are compared against a stored value which is regularly updated when no faults are present. In this way, the cylinder contribution for each cylinder can be determined.

PACCAR MX (2004 Emissions) Fault Code: P127A EGR Pressure Difference – Data Valid but Too Low

SET CONDITIONS:
The PCI ECU (D420) detects that the measured EGR gas mass flow is too low for the commanded EGR valve position for more than 20 seconds.

DIAGNOSTIC CONDITION:
This diagnostic runs:
1. When the engine speed is between 1050 and 1900 rpm and
2. The engine is running at a steady load and
3. The engine mode is SCR heating or SCR high efficiency mode or standard mode.

CORRESPONDING OBD READINESS MONITOR:
None

RESET CONDITION:
This DTC changes to inactive when the fault is no longer detected.

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? (Can be pending, inactive or active)
– No, repair successful
– Yes, repair unsuccessful

POSSIBLE CAUSES:
1. Leaking EGR system
2. Clogged EGR system
3. Contaminated EGR pressure difference sensor venturi
4. Sticking EGR valve
5. EGR pressure difference sensor deviation

ADDITIONAL INFORMATION:
1. The engine NOx emission is, among others, controlled by varying the EGR gas mass flow toward the inlet manifold of the engine.

2. The EGR gas mass flow is calculated using the EGR pressure difference sensor (F751) and the EGR temperature sensor (F749).

3. EGR gas mass flow toward the inlet manifold of the engine is controlled by the EGR valve module (L095).

IMPORTANT: The EGR position does not necessarily indicate the amount of EGR flow to the inlet manifold. The amount of EGR gas fed back mainly depends on the pressure difference between the pressure before turbine and the boost pressure, in combination with the EGR valve position.

PACCAR MX (2004 Emissions) Fault Code: P127B EGR Pressure Difference – Data Valid but Too High

SET CONDITIONS:
The PCI ECU (D420) detects that the measured EGR gas mass flow is too high for the commanded EGR valve position for more than 20 seconds.

DIAGNOSTIC CONDITION:
This diagnostic runs:
1. When the engine speed is between 1050 and 1900 rpm and
2. The engine is running at a steady load and
3. The engine mode is SCR heating or SCR high efficiency mode or standard mode.

CORRESPONDING OBD READINESS MONITOR:
None

RESET CONDITION:
This DTC changes to inactive when the fault is no longer detected.

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? (Can be pending, inactive or active)
– No, repair successful
– Yes, repair unsuccessful

POSSIBLE CAUSES:
1. Contaminated EGR pressure difference sensor venturi
2. Sticking EGR valve
3. EGR pressure difference sensor deviation

ADDITIONAL INFORMATION:
1. The engine NOx emission is, among others, controlled by varying the EGR gas mass flow toward the inlet manifold of the engine.

2. The EGR gas mass flow is calculated using the EGR pressure difference sensor (F751) and the EGR temperature sensor (F749).

3. EGR gas mass flow toward the inlet manifold of the engine is controlled by the EGR valve module (L095).

IMPORTANT: The EGR valve position does not just indicate the amount of EGR flow to the inlet manifold. The amount of EGR gas fed back mainly depends on the pressure difference between the pressure before turbine and the boost pressure, in combination with the EGR valve position.

PACCAR MX (2004 Emissions) Fault Code: P127C EGR Pressure Difference – Data Erratic, Intermittent, or Incorrect

SET CONDITIONS:
The PCI ECU (D420) detects that the measured EGR gas mass flow differs too much from the expected EGR gas mass flow for more than 40 seconds.

DIAGNOSTIC CONDITION:
This diagnostic runs:
1. Engine speed is between 1050 and 1900 rpm and
2. EGR valve position is more than 25% and
3. Pressure difference between boost pressure and pressure before turbine is more than 0.25 bar [3.6 PSI] and
4. The engine mode is SCR heating or SCR high efficiency mode or standard mode.

CORRESPONDING OBD READINESS MONITOR:
None

RESET CONDITION:
This DTC changes to inactive when the fault is no longer detected.

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? (Can be pending, inactive or active)
– No, repair successful
– Yes, repair unsuccessful

POSSIBLE CAUSES:
1. Contaminated EGR pressure difference sensor venturi
2. EGR pressure difference sensor deviation
3. EGR temperature sensor deviation
4. Boost temperature sensor deviation

ADDITIONAL INFORMATION:
1. One way in which the engine NOx emission is controlled is by varying the EGR gas mass flow toward the inlet manifold of the engine.

2. The EGR gas mass flow is calculated using the EGR pressure difference sensor (F751), EGR temperature sensor (F749) and boost temperature sensor (F804).

3. EGR gas mass flow toward the inlet manifold of the engine is controlled by the EGR valve module (L095).

IMPORTANT: The EGR valve position does not just indicate the amount of EGR flow to the inlet manifold. The amount of EGR gas fed back mainly depends on the pressure difference between the pressure before turbine and the boost pressure, in combination with the EGR valve position.

PACCAR MX (2004 Emissions) Fault Code: P128E Common Rail Fuel Pressure Control – Incorrect

SET CONDITIONS:
The PCI ECU (D420) detects that the measured rail pressure is more than 1000 bar higher than the commanded rail pressure for more than 5 seconds.

DIAGNOSTIC CONDITION:
This diagnostic runs when the rail pressure operating state is: Rail discharge.

RESET CONDITION:
This DTC changes to inactive when the fault is no longer detected.

POSSIBLE CAUSES:
1. Blocked common rail pressure release valve return pipe
2. Malfunction on common rail pressure release valve

ADDITIONAL INFORMATION:
1. The rail pressure is closed-loop controlled. A comparison is made between the rail pressure commanded by the ECU and the rail pressure feedback measured by the common rail pressure sensor.

2. The common rail pressure release valve (L094) is used to decrease the rail pressure rapidly (dumping) during normal operation.
3. The rail pressure is measured in the common rail by the common rail pressure sensor (F854).