Inlet Air Heater Fault Codes of Volvo Engine

May. 17, 2018

MID 128, PID 45 Inlet air heater status

MID 128: Engine control unit

FMI 3 – Voltage above normal or short circuit to higher voltage
Fault code explanation:	Faulty sensor / Faulty sensor circuit
Fault indication:	DCU: Engine warning in DCU display. CIU: Flash code Flash code Electrical fault: 5.4 Value fault: None
Symptom:	Preheat relay never activated. White smoke for cold start. Start problems in cold climate.
Conditions for fault code:	The voltage on pin B25 on the EMS 2 is higher than normal.
Possible reason:	Short circuit to B+ in cable harness between B25 and preheat relay.
Suitable action:	1 Check cable harness and connectors between B25 and preheat relay.

FMI 4 – Voltage below normal or short circuit to lower voltage
Fault code explanation:	Faulty sensor / Faulty sensor circuit
Fault indication:	DCU: Engine warning in DCU display. CIU: Flash code Flash code Electrical fault: 5.4 Value fault: None
Symptom:	Induction air is hot. Preheat relay is impossible to turn off. Preheat fuse will break.
Conditions for fault code:	The voltage on pin B25 on the EMS 2 is lower than normal.
Possible reason:	Short circuit to battery negative in cable harness between B25 and preheat relay (the relay pulls).
Suitable action:	1 Check cable harness and connectors between B25 and preheat relay.

FMI 5 – Current below normal or open circuit
Fault code explanation:	Faulty sensor / Faulty sensor circuit
Fault indication:	DCU: Engine warning in DCU display. CIU:Flash code Flash code Electrical fault: 5.4 Value fault: None
Symptom:	Preheat relay never activated. White smoke for cold start. Start problems in cold climate.
Possible reason:	• Broken preheat relay. • An open circuit in cable harness between B25 and preheat relay. • An open circuit in cable harness between B57 and B60 and preheat relay.
Suitable action:	1 Check that preheat relay coil is not broken. 2 Check the contact pressure in socket B25, socket B57 and B60 in the engine connector. 3 Check cable harness and connectors between B25, B57 and B60 and preheat relay.
Measurements:	• Checking the preheat relay page 115

Circuit description

In cold climate the intake air need too be preheated. This is either done for GE engines by the preheater which is located in the inlet manifoldor or for VE engines by the glowplugs that are mounted in the cylinderhead. The preheat function is activated/deactivated by the engine control unit via the preheat relay. While the relay is not activated the potential on B25 is equal to battery voltage. When the preheat function is activated B25 alter its potential and the relay activates. A sense wire is connected between the preheater relay output and B7. The sense wire checks that the preheat element and the preheat fuse are not damaged.

MID 128, PID 94 Fuel Delivery Pressure

MID 128: Engine control unit

FMI 1 – Data valid but below operational range
Fault code explanation:	Fuel pressure is too low.
Fault indication:	DCU: Engine warning in DCU display. CIU: Flash code Flash code Electrical fault: 3.6 Value fault: 3.8
Symptom:	None.
Conditions for fault code:	The fuel pressure alarm depends on the engine revolution.
Suitable action:	1 Check fuel level. 2 Open all fuel cocks and check that no leakage occurs. 3 Check drive belt adjustment. 4 Change all fuel filters. (pre- and fine filter) 5 Check that no fuel hose is squeezed or folded. 6 Check function of fuel pressure sensor by control measuring the fuel pressure. (see workshop manual) 7 Check fuel feed pump. 8 Change fuel pressure release valve. (see workshop manual)
Measurements:	• Checking fuel pressure sensor page 117

FMI 3 – Voltage above normal or short circuit to higher voltage
Fault code explanation:	Faulty sensor / Fault in sensor circuit
Fault indication:	DCU: Engine warning in DCU display. CIU: Flash code Flash code Electrical fault: 3.6 Value fault: 3.8
Symptom:	None.
Conditions for fault code:	The voltage on pin B16 on the EMS 2 is more than 4,75 Volt.
Possible reason:	• An open circuit in fuel sensor negative cable. • Short circuited fuel sensor signal cable to 5V voltage or to battery voltage. • Faulty sensor.
Suitable action:	1 Check contact pressure in socket 18 in the engine connector B. Also check contact pressure in connector at fuel pressure sensor. 2 Check cable harness and connectors between fuel sensor and EMS 2. 3 Check function of fuel pressure sensor.
Measurements:	• Checking supply cable, fuel sensor page 115 • Checking negative cable, fuel sensor page 116 • Checking signal cable, fuel sensor page 117 • Checking fuel pressure sensor page 117

FMI 5 – Current below normal or open circuit
Fault code explanation:	Faulty sensor / Fault in sensor circuit
Fault indication:	DCU: Engine warning in DCU display. CIU: Flash code Flash code Electrical fault: 3.6 Value fault: 3.8
Symptom:	None.
Conditions for fault code:	The voltage on pin B16 on the EMS 2 is less than 0.07 Volt.
Possible reason:	• An open circuit in fuel sensor 5V supply cable. • An open circuit in fuel sensor signal cable. • Short circuited sensor signal cable to battery negative. • Faulty sensor.
Suitable action:	1 Check contact pressure in socket 16 and 17 in the engine connector B. Also check contact pressure in connector at fuel pressure sensor. 2 Check cable harness and connectors between fuel sensor and EMS 2. 3 Check function of fuel pressure sensor.
Measurements:	• Checking supply cable, fuel sensor page 115 • Checking negative cable, fuel sensor page 116 • Checking signal cable, fuel sensor page 117 • Checking fuel pressure sensor page 117

FMI 7 – Mechanical fault. The system responds incorrectly.
Fault code explanation:	Fuel pressure is critically low
Fault indication:	DCU: Engine warning in DCU display. CIU: Flash code Flash code Electrical fault: 3.6 Value fault: 3.8
Symptom:	None.
Conditions for fault code:	The fuel pressure alarm depends on the engine revolution.
Suitable action:	1 Check fuel level. 2 Open all fuel cocks and check that no leakage occurs. 3 Check drivebelt adjustment. 4 Change all fuel filters. (pre- and fine filter) 5 Chech that no fuel hose is squeezed or folded. 6 Check functionof fuel pressure sensor by control measuring the fuel pressure. (see workshop manual) 7 Check fuel feed pump. 8 Change fuel pressure release valve. (see workshop manual)
Measurements:	• Checking fuel pressure sensor page 117

Circuit description

The sensor is an active sensor, i.e. the sensor must receive operating voltage. Pin B17 on the engine control unit provides pin 1 on the sensor with an operating voltage of +5 Volt. Pin 4 on the sensor is connected to battery negative via pin B18 on the engine control unit. The output signal from the pressure sensor, pin 2 on the sensor to pin B16 on the EMS 2, is a voltage signal that is proportional to the fuel pressure.