Volvo

The aftertreatment control module (ACM) uses the aftertreatment diesel exhaust fluid (DEF) dosing pressure sensor value to adjust and maintain DEF pressure at the DEF dosing valve by controlling DEF pump speed. If the pressure decreases below expected value when the pump is in initial pressure build-up mode or if the pressure increases above expected value when pump is in idle speed mode, the ACM considers DEF pressure outside of normal operating range and indicates a malfunction in a DEF dosing pressure sensor.

Conditions for diagnostic trouble code (DTC):
1) DEF dosing pressure too high based on existing conditions

Observable symptoms
1) Low aftertreatment diesel exhaust fluid (DEF) solution consumption

Probable cause
1) Clogged internal bleed orifice
2) Blocked return line (damaged or frozen)
3) Crystallization in filter
4) Aftertreatment DEF Dosing Pressure Sensor

The Idle Validation Switch is open at the idle position and transmits no voltage to the (VECU) Vehicle Electronic Control Unit. At approximately 1-13% pedal position the Idle Validation Switch closes and completes the circuit to the (VECU) Vehicle Electronic Control Unit.
The (VECU) Vehicle Electronic Control Unit then sends a voltage signal to the Engine Control Module (ECM) indicating accelerator pedal position. If both communication links (J1939, J1587) are faulty the pedal demand functionality enters limp-home. During limp-home the (IVS) Idle Validation Switch is used for ramping requested torque.

Conditions for diagnostic trouble code (DTC):
1) Accelerator pedal (AP) released
2) Short circuit to battery voltage on A14.EB:15

Observable symptoms
1) The limp home mode does not function
2) Yellow check lamp illuminated

Probable cause
1) Short circuit to voltage supply, signal wire
2) Connector
3) Accelerator pedal
4) Engine control module (ECM)

The Idle Validation Switch is open at the idle position and transmits no voltage to the (VECU) Vehicle Electronic Control Unit. At approximately 1-13% pedal position the Idle Validation Switch closes and completes the circuit to the (VECU) Vehicle Electronic Control Unit.
The (VECU) Vehicle Electronic Control Unit then sends a voltage signal to the Engine Control Module (ECM) indicating accelerator pedal position. If both communication links (J1939, J1587) are faulty the pedal demand functionality enters limp-home. During limp-home the (IVS) Idle Validation Switch is used for ramping requested torque.

Conditions for diagnostic trouble code (DTC):
1) Accelerator pedal pressed down more than 50?%
2) Short circuit to ground on A14.EB:15
3) Open circuit between ECM: Engine Control Module (ECM) and Vehicle Control Unit (VECU)

Observable symptoms
1) The limp home mode does not function
2) Yellow check lamp illuminated

Probable cause
1) Open circuit on signal wire
2) Connector
3) Accelerator pedal
4) Engine control module (ECM)

The preheat Relay controls the preheater from an electric signal from the Engine Control Module (ECM). This function is used to warm up the inlet air during cold conditions. This provides more reliable starting and reduces exhaust emissions during cold starts. Vehicles can be equipped with or without the preheater.

Conditions for diagnostic trouble code (DTC):
1) Output activated
2) Short circuit to battery voltage on A14.EB:25

Observable symptoms
1) Intake air heater (IAH) relay never activated
2) Difficult to start in extreme cold
3) White smoke at cold start

Probable cause
1) Engine wiring harness
2) Connector
3) Intake air heater (IAH) relay

The preheat Relay controls the preheater from an electric signal from the Engine Control Module (ECM). This function is used to warm up the inlet air during cold conditions. This provides more reliable starting and reduces exhaust emissions during cold starts. Vehicles can be equipped with or without the preheater.

Conditions for diagnostic trouble code (DTC):
1) Output activated
2) Short circuit to battery voltage on A14.EB:25

Observable symptoms
1) Intake air heater (IAH) relay never activated
2) Difficult to start in extreme cold
3) White smoke at cold start

Probable cause
1) Engine wiring harness
2) Connector
3) Intake air heater (IAH) relay

The preheat Relay controls the preheater from an electric signal from the Engine Control Module (ECM). This function is used to warm up the inlet air during cold conditions. This provides more reliable starting and reduces exhaust emissions during cold starts. Vehicles can be equipped with or without the preheater.

Conditions for diagnostic trouble code (DTC):
1) Output not activated
2) Open circuit

Observable symptoms
1) Intake air heater (IAH) relay never activated
2) Difficult to start in extreme cold
3) White smoke at cold start

Probable cause
1) Engine wiring harness
2) Connector
3) Fuse: FE8
4) Intake air heater (IAH) relay

This diagnostic trouble code (DTC) detects faults in the main software. Faulty main software can result in engine no start symptoms.

Conditions for diagnostic trouble code (DTC):
1) Faulty data in program memory

Observable symptoms
1) Engine does not start

Probable cause
1) Engine control module (ECM)