Group 28 Troubleshooting
MID 128 PID 45 Preheater Status
The preheat relay is provided battery voltage at all times through the supply wire. If the
EECU requests preheat operation (based on engine temperature), the control wire will
be grounded through the EECU. Preheating is standard on the D7C engine with one
preheat relay/element. Preheating is optional on the D12B engine with two preheat re-
lays/elements.
Fault Codes
FMI 3
Short circuit to battery voltage.
Conditions for fault code:
•
Output activated.
•
Short circuit to battery voltage on EB31.
Possible cause:
•
Short circuit to battery voltage on wire between pre-
heating relay and EECU.
•
Short circuit in the preheating relay.
Reaction from the EECU:
•
Fault code is set.
•
Yellow lamp is requested.
•
The EECU switches off the output.
Noticeable external symptom:
•
Yellow lamp lights up.
•
The preheating relay is not activated.
•
White smoke for cold start.
•
Difficult to start in extreme cold.
FMI 4
Short circuit to ground.
Conditions for fault code:
•
Output switched off.
•
Short circuit to ground on EB31.
Possible cause:
•
Short circuit to ground on wire between preheating
relay and EECU.
Reaction from the EECU:
•
Fault code is set.
•
Yellow lamp is requested.
Noticeable external symptom:
•
Yellow lamp lights up.
•
The intake air is warm since the preheating relay is
on all the time.
•
High current consumption.
FMI 5:
Break
Conditions for fault code:
•
Output switched off.
•
Open circuit.
Possible cause:
•
Blown fuse to the supply for preheating relay.
•
Open circuit in wire between EECU and preheating
relay.
•
Open circuit in the preheating relay.
•
Open circuit in supply wire to preheating relay.
Reaction from the EECU:
•
Fault code is set.
•
Yellow lamp is requested.
•
The EECU switches off the output.
Noticeable external symptom:
•
Yellow lamp lights up.
•
The preheating relay is not activated.
•
White smoke for cold start.
•
Difficult to start in extreme cold.
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