Paccar

Verify the electronic control module (ECM) calibration is correct. Check the calibration revision history found on QuickServe® Online for applicable fixes to the calibration stored in the ECM. If necessary, recalibrate the ECM.

Possible causes:

1)Signal circuit open or shorted to ground in the OEM harness or sensor
2)Supply line open or shorted to ground.

Possible repairs:

1)Replace the OEM pressure sensor.
2)Repair or replace the OEM harness.
3)Replace the ECM.

Verify the electronic control module (ECM) calibration is correct. Check the calibration revision history found on QuickServe™ Online for applicable fixes to the calibration stored in the ECM. If necessary, calibrate the ECM.

1)Fault activation: The ECM senses current as each injector is actuated. If the ECM detects a persistent circuit error on an injector circuit, this fault will become active. If a circuit error is determined to cause excessive current, the ECM will disable the injection event for the cylinder(s) that is faulty.
2)Fault deactivation: The ECM will attempt to enable any disabled injector circuit whenever the engine is started and approximately once per minute while the engine is running. If an injector circuit fault is active and the faulty condition is repaired, the fault will become inactive once the engine is restarted or if the engine is permitted to idle for more than 1 minute.
3)If a fault condition is intermittent and especially if more than one injector fault code is in the ECM memory, look for a wire harness that can short to components inside the rocker housing or for a short circuit to ground in the injector solenoid.
4)If more than one injector fault code is occurring and the faults occur for injector circuits in the same bank, a short circuit exists.

Causes of a single injector fault are:

1)An open circuit in the engine harness(es) or injector solenoid
2)High resistance in a single injector or injector solenoid
3)Extremely low resistance in an injector solenoid (injector shorted internally but not to ground)
4)Damaged ECM.
5)If a fault condition is intermittent and especially if more than one injector fault code is in the ECM memory, look for a wire harness that can short to components inside the rocker housing or a short circuit to ground in the injector solenoid.

Causes of multiple injector fault codes in the same bank of injectors are:

1)Short circuit in the engine harness(es) – either shorts to ground or to other wires in the engine harness
2)Short circuit in any of the three injectors in the bank – shorts to ground
3)Damaged ECM.

Possible repairs:

1)Repair or replace the engine harness.
2)Repair or replace the injector harness.
3)Repair or replace the damaged component.
4)Replace the ECM.
5)Replace injector number 1.
6)Replace injector number 2.
7)Replace injector number 3.

Verify the electronic control module (ECM) calibration is correct. Check the calibration revision history found on QuickServe™ Online for applicable fixes to the calibration stored in the ECM. If necessary, calibrate the ECM.

1)Fault activation: The ECM senses current as each injector is actuated. If the ECM detects a persistent circuit error on an injector circuit, this fault will become active. If a circuit error is determined to cause excessive current, the ECM will disable the injection event for the cylinder(s) that is faulty.
2)Fault deactivation: The ECM will attempt to enable any disabled injector circuit whenever the engine is started and approximately once per minute while the engine is running. If an injector circuit fault is active and the faulty condition is repaired, the fault will become inactive once the engine is restarted or if the engine is permitted to idle for more than 1 minute.
3)If a fault condition is intermittent and especially if more than one injector fault code is in the ECM memory, look for a wire harness that can short to components inside the rocker housing or for a short circuit to ground in the injector solenoid.
4)If more than one injector fault code is occurring and the faults occur for injector circuits in the same bank, a short circuit exists.

Causes of a single injector fault are:

1)An open circuit in the engine harness(es) or injector solenoid
2)High resistance in a single injector or injector solenoid
3)Extremely low resistance in an injector solenoid (injector shorted internally but not to ground)
4)Damaged ECM.
5)If a fault condition is intermittent and especially if more than one injector fault code is in the ECM memory, look for a wire harness that can short to components inside the rocker housing or a short circuit to ground in the injector solenoid.

Causes of multiple injector fault codes in the same bank of injectors are:

1)Short circuit in the engine harness(es) – either shorts to ground or to other wires in the engine harness
2)Short circuit in any of the three injectors in the bank – shorts to ground
3)Damaged ECM.

Possible repairs:

1)Repair or replace the engine harness.
2)Repair or replace the injector harness.
3)Repair or replace the damaged component.
4)Replace the ECM.
5)Replace injector number 4.
6)Replace injector number 5.
7)Replace injector number 6.

Verify the electronic control module (ECM) calibration is correct. Check the calibration revision history found on QuickServe™ Online for applicable fixes to the calibration stored in the ECM. If necessary, calibrate the ECM.

1)Fault activation: The ECM senses current as each injector is actuated. If the ECM detects a persistent circuit error on an injector circuit, this fault will become active. If a circuit error is determined to cause excessive current, the ECM will disable the injection event for the cylinder(s) that is faulty.
2)Fault deactivation: The ECM will attempt to enable any disabled injector circuit whenever the engine is started and approximately once per minute while the engine is running. If an injector circuit fault is active and the faulty condition is repaired, the fault will become inactive once the engine is restarted or if the engine is permitted to idle for more than 1 minute.
3)If a fault condition is intermittent and especially if more than one injector fault code is in the ECM memory, look for a wire harness that can short to components inside the rocker housing or for a short circuit to ground in the injector solenoid.
4)If more than one injector fault code is occurring and the faults occur for injector circuits in the same bank, a short circuit exists.

Causes of a single injector fault are:

1)An open circuit in the engine harness(es) or injector solenoid
2)High resistance in a single injector or injector solenoid
3)Extremely low resistance in an injector solenoid (injector shorted internally but not to ground)
4)Damaged ECM.
5)If a fault condition is intermittent and especially if more than one injector fault code is in the ECM memory, look for a wire harness that can short to components inside the rocker housing or a short circuit to ground in the injector solenoid.

Causes of multiple injector fault codes in the same bank of injectors are:

1)Short circuit in the engine harness(es) – either shorts to ground or to other wires in the engine harness
2)Short circuit in any of the three injectors in the bank – shorts to ground
3)Damaged ECM.

Possible repairs:

1)Repair or replace the engine harness.
2)Repair or replace the injector harness.
3)Repair or replace the damaged component.
4)Replace the ECM.
5)Replace injector number 1.
6)Replace injector number 2.
7)Replace injector number 3.

Verify the electronic control module (ECM) calibration is correct. Check the calibration revision history found on QuickServe™ Online for applicable fixes to the calibration stored in the ECM. If necessary, calibrate the ECM.

1)Fault activation: The ECM senses current as each injector is actuated. If the ECM detects a persistent circuit error on an injector circuit, this fault will become active. If a circuit error is determined to cause excessive current, the ECM will disable the injection event for the cylinder(s) that is faulty.
2)Fault deactivation: The ECM will attempt to enable any disabled injector circuit whenever the engine is started and approximately once per minute while the engine is running. If an injector circuit fault is active and the faulty condition is repaired, the fault will become inactive once the engine is restarted or if the engine is permitted to idle for more than 1 minute.
3)If a fault condition is intermittent and especially if more than one injector fault code is in the ECM memory, look for a wire harness that can short to components inside the rocker housing or for a short circuit to ground in the injector solenoid.
4)If more than one injector fault code is occurring and the faults occur for injector circuits in the same bank, a short circuit exists.

Causes of a single injector fault are:

1)An open circuit in the engine harness(es) or injector solenoid
2)High resistance in a single injector or injector solenoid
3)Extremely low resistance in an injector solenoid (injector shorted internally but not to ground)
4)Damaged ECM.
5)If a fault condition is intermittent and especially if more than one injector fault code is in the ECM memory, look for a wire harness that can short to components inside the rocker housing or a short circuit to ground in the injector solenoid.

Causes of multiple injector fault codes in the same bank of injectors are:

1)Short circuit in the engine harness(es) – either shorts to ground or to other wires in the engine harness
2)Short circuit in any of the three injectors in the bank – shorts to ground
3)Damaged ECM.

Possible repairs:

1)Repair or replace the engine harness.
2)Repair or replace the injector harness.
3)Repair or replace the damaged component.
4)Replace the ECM.
5)Replace injector number 4.
6)Replace injector number 5.
7)Replace injector number 6.

Verify the electronic control module (ECM) calibration is correct. Check the calibration revision history found on QuickServe™ Online for applicable fixes to the calibration stored in the ECM. If necessary, calibrate the ECM.

1)Fault activation: The ECM senses current as each injector is actuated. If the ECM detects a persistent circuit error on an injector circuit, this fault will become active. If a circuit error is determined to cause excessive current, the ECM will disable the injection event for the cylinder(s) that is faulty.
2)Fault deactivation: The ECM will attempt to enable any disabled injector circuit whenever the engine is started and approximately once per minute while the engine is running. If an injector circuit fault is active and the faulty condition is repaired, the fault will become inactive once the engine is restarted or if the engine is permitted to idle for more than 1 minute.
3)If a fault condition is intermittent and especially if more than one injector fault code is in the ECM memory, look for a wire harness that can short to components inside the rocker housing or for a short circuit to ground in the injector solenoid.
4)If more than one injector fault code is occurring and the faults occur for injector circuits in the same bank, a short circuit exists.

Causes of a single injector fault are:

1)An open circuit in the engine harness(es) or injector solenoid
2)High resistance in a single injector or injector solenoid
3)Extremely low resistance in an injector solenoid (injector shorted internally but not to ground)
4)Damaged ECM.
5)If a fault condition is intermittent and especially if more than one injector fault code is in the ECM memory, look for a wire harness that can short to components inside the rocker housing or a short circuit to ground in the injector solenoid.

Causes of multiple injector fault codes in the same bank of injectors are:

1)Short circuit in the engine harness(es) – either shorts to ground or to other wires in the engine harness
2)Short circuit in any of the three injectors in the bank – shorts to ground
3)Damaged ECM.

Possible repairs:

1)Repair or replace the engine harness.
2)Repair or replace the injector harness.
3)Repair or replace the damaged component.
4)Replace the ECM.
5)Replace injector number 1.
6)Replace injector number 2.
7)Replace injector number 3.

Verify the electronic control module (ECM) calibration is correct. Check the calibration revision history found on QuickServe™ Online for applicable fixes to the calibration stored in the ECM. If necessary, calibrate the ECM.

1)Fault activation: The ECM senses current as each injector is actuated. If the ECM detects a persistent circuit error on an injector circuit, this fault will become active. If a circuit error is determined to cause excessive current, the ECM will disable the injection event for the cylinder(s) that is faulty.
2)Fault deactivation: The ECM will attempt to enable any disabled injector circuit whenever the engine is started and approximately once per minute while the engine is running. If an injector circuit fault is active and the faulty condition is repaired, the fault will become inactive once the engine is restarted or if the engine is permitted to idle for more than 1 minute.
3)If a fault condition is intermittent and especially if more than one injector fault code is in the ECM memory, look for a wire harness that can short to components inside the rocker housing or for a short circuit to ground in the injector solenoid.
4)If more than one injector fault code is occurring and the faults occur for injector circuits in the same bank, a short circuit exists.

Causes of a single injector fault are:

1)An open circuit in the engine harness(es) or injector solenoid
2)High resistance in a single injector or injector solenoid
3)Extremely low resistance in an injector solenoid (injector shorted internally but not to ground)
4)Damaged ECM.
5)If a fault condition is intermittent and especially if more than one injector fault code is in the ECM memory, look for a wire harness that can short to components inside the rocker housing or a short circuit to ground in the injector solenoid.

Causes of multiple injector fault codes in the same bank of injectors are:

1)Short circuit in the engine harness(es) – either shorts to ground or to other wires in the engine harness
2)Short circuit in any of the three injectors in the bank – shorts to ground
3)Damaged ECM.

Possible repairs:

1)Repair or replace the engine harness.
2)Repair or replace the injector harness.
3)Repair or replace the damaged component.
4)Replace the ECM.
5)Replace injector number 4.
6)Replace injector number 5.
7)Replace injector number 6.

Verify the electronic control module (ECM) calibration is correct. Check the calibration revision history found on QuickServe® Online for applicable fixes to the calibration stored in the ECM. If necessary, recalibrate the ECM.

Two different failure modes of the engine coolant temperature sensor can trigger this fault code. Either the sensor is not reading ambient air temperature after an extended period with the engine not running or the engine coolant temperature is not changing with engine operating conditions.

Possible causes:

1)Stuck in-range engine coolant temperature sensor
2)High resistance in the engine coolant temperature sensor signal or return lines.

Possible repairs:

1)Replace the thermostat.
2)Replace the engine coolant temperature sensor.
3)Replace the ECM.
4)Repair or replace the engine harness.

Verify the electronic control module (ECM) calibration is correct. Check the calibration revision history found on QuickServe® Online for applicable fixes to the calibration stored in the ECM. If necessary, recalibrate the ECM.

Make sure the ECM unswitched battery supply is coming directly from the battery and not the starter. If unswitched power is coming from the starter, it is possible for the battery voltage to drop low enough during cranking to set this fault active.

This fault can also be caused by resistance in the ECM battery supply (+) or (-) circuits. Resistance in these circuits can cause the voltage level at the ECM input to drop low enough to set Fault Code 343 active.

Possible repairs:

1)Tighten the loose connections and clean the terminals.
2)Charge or replace the battery.
3)Repair or replace the OEM harness.
4)Replace the blown fuse(s).
5)Repair or replace the OEM power harness from the OEM power connector to the batteries.
6)Repair or replace the ECM power harness.
7)Repair or replace the OEM harness.
8)Replace the ECM.