Volvo Symptom D12D US02 Service Manual page 41

Group 20
so, has the truck been serviced or repaired according
to the instructions?
•
Some countries have stricter environmental regulations
for diesel fuels than others. These fuels give lower
exhaust emissions than standard fuels, yet often also
reduced engine power output and slightly increased
fuel consumption. Therefore the type of fuel must be
considered when complaints concern slightly lower
power output or higher fuel consumption.
•
Check if the vehicle has been in the workshop before.
Check what checks and repairs have been carried
out. This must be done before fault-tracing for engine
Fault Tracing
Intermittent faults can be difficult to trace since the fault
may not occur when the vehicle is brought in to be
checked.
Fault tracing should be performed based on what the
driver has experienced. The information that the driver
has provided in conjunction with the gathering of factual
data should form the basis of how the problem should
be resolved.
Whenever possible, try to recreate the problem in an
environment and situation similar to the one described
by the driver.
Abnormally High Fuel Consumption
Related Symptoms
In some cases, other symptoms may be noticed. In these
cases, other Service Information may be helpful for fault
tracing:
•
Group 20: Low power output
The following checks should be carried out in order until
the fault is found. These checks also can help eliminate
components with no faults or malfunctions. The number of
tests and the order depends on the following: results from
tests and fault codes, vehicle conditions, vehicle service
and repair history, other symptoms, and information from
the driver.
Step 1: Fault Code Readings
Active and inactive fault codes which are registered can
point to faults, but can also facilitate tracing the symptom.
C2002639
D
related high fuel consumption. Check other vehicle
components:
•
All axles (complete combination) are parallel
•
No brakes are applied (or misaligned brakes)
•
Wheel alignment is correct
•
Tires have correct air pressure
•
Tires do not have excessive wear or rough wear
patterns
•
Compressor charging time is within specifications.
The compressed air system is not leaking
•
The air conditioning (A/C) compressor is not
engaged constantly
•
The fan clutch is operating properly.
Begin by determining if anything has recently happened
to the vehicle that could point to the electrical system,
but which does not have anything to do with the engine
control system.
For specific symptoms, see:
•
"Abnormally High Fuel Consumption" page 37
"High Fuel Consumption, Fault Tracing" page 36
•
"Step 1: Fault Code Readings" page 37
•
"Step 2: Visual Inspection (System Checks)" page 38
•
"Step 3: VCADS Pro Tests" page 38
•
"Step 4: Component and Function Checks" page 40
"High Fuel Consumption, Fault Tracing" page 36
Freeze frames with information for specific fault codes
can also assist in tracing causes of the symptom.
Fault tracing using relevant service information
must always be carried out for relevant fault codes.
Components/functions of special interest:
•
MID 128, Engine ECU
PID 26
PID 94
SID 1–6
SID 33
PPID 35
Fan speed %
Fuel supply pressure
Unit injectors
Fan control
EGR Mass flow (D16D)
37