december2022 - A8
FAULT CODES
Diagnosing faults on modern vehicles
The complexity of today's vehicles means technicians are flooded with additional data
when diagnosing vehicle faults. Here are ways and tools to help diagnose these faults.
By Damien Coleman
VEHICLE
PRE-2002
Number of
Systems
Engine
Fault Codes
Engine Data
Parameters
Engine
Special
Functions
≈6
<50
<30
<3
2022
VEHICLE
25 - 40*
>2000
>100
>20
*Depending on options and trim level.
under-boost fault will only be set after
a test drive.
M
otor vehicles have become
increasingly more complex
over the last two decades
to meet ever-tightening emissions
regulations, increased fuel economy
requirements, and passenger comfort
and safety.
This added complexity means technicians
are flooded with additional data
when diagnosing vehicle faults. Below is
a table outlining the difference between
a modern vehicle and a vehicle from 20
years ago; this is only a high-level example
to illustrate the differences.
FAULT CODES
However, with all the additional fault
codes and data parameters, the technician
is given more information that can
help quickly and accurately diagnose any
8 DECEMBER 2022 VehicleServicePros.com
faults. For most fault codes, there are
several possible sub-codes. These subcodes
give the technician an indication
of the condition which caused the fault
code to be stored. An example of this is
shown below for turbocharger system
fault codes:
* Turbocharger boost pressure - Negative
deviation (under-boost)
* Turbocharger boost pressure -
Positive deviation (over-boost)
* Turbocharger boost control circuit
- Voltage high
* Turbocharger boost control circuit
- Voltage low
If a fault code won't clear with the
ignition on and engine off, or the fault
returns immediately once the ignition is
switched on, the issue is most likely not
mechanical in nature. An over-boost or
LIVE DATA
Many data lists will have two parameters
for specific components or subsystems.
In the screenshot (on page 9)
we have 'actual' and 'specific' boost pressure.
Comparing these data parameters
is important to ensure the vehicle is
operating under the conditions expected
by the management system. There will
be a certain amount of latency between
these parameters, but the returned values
should be similar.
Command and feedback are also
evident here with the data parameters
for the boost pressure actuator, activation
value (%), boost pressure actuator,
and feedback value (%). This shows the
control from the engine control module
acting on the turbocharger vane position
actuator and the feedback from the
turbocharger position sensor, which is
inferred as a percentage.
* Parameter 1 - Actual boost pressure
* Parameter 2 - Specific boost pressure
* Parameter 3 - Boost pressure actuator,
activation value (%)
Albertshakirov | Dreamstime.com
http://www.Dreamstime.com
http://www.VehicleServicePros.com
december2022
Table of Contents for the Digital Edition of december2022
Editor's Note: The technician shortage is getting real
Sneak Peek
Most Wanted
Electric vehicles - coming to a shop near you
In Focus
Diagnostic Tech: Using digital tools to reduce the friction of running a shop
Show Me Your Truck: 'Look at that Bad Larry!'
Go Sell Something: Writing a sales pitch
Driving Sales
Tales From the Road: An entrepreneurial spirit
SEMA/AAPEX Wrap-up
Diagnosing Progress
Common diagnostics and trends in hybrid and electric vehicles
Diagnosing faults on modern vehicles
The real cause of P0420/P0430 DTCs
How diagnostic tools cut through the ADAS confusion
When the tools become the tutor
Diagnostic products
december2022 - 1
december2022 - 2
december2022 - 3
december2022 - Editor's Note: The technician shortage is getting real
december2022 - 5
december2022 - Sneak Peek
december2022 - 7
december2022 - 8
december2022 - 9
december2022 - 10
december2022 - 11
december2022 - Most Wanted
december2022 - 13
december2022 - Electric vehicles - coming to a shop near you
december2022 - 15
december2022 - 16
december2022 - 17
december2022 - 18
december2022 - 19
december2022 - 20
december2022 - 21
december2022 - In Focus
december2022 - 23
december2022 - 24
december2022 - 25
december2022 - Diagnostic Tech: Using digital tools to reduce the friction of running a shop
december2022 - 27
december2022 - 28
december2022 - 29
december2022 - Show Me Your Truck: 'Look at that Bad Larry!'
december2022 - 31
december2022 - Go Sell Something: Writing a sales pitch
december2022 - 33
december2022 - 34
december2022 - Driving Sales
december2022 - 36
december2022 - 37
december2022 - Tales From the Road: An entrepreneurial spirit
december2022 - 39
december2022 - SEMA/AAPEX Wrap-up
december2022 - 41
december2022 - 42
december2022 - 43
december2022 - 44
december2022 - A1
december2022 - A2
december2022 - A3
december2022 - Diagnosing Progress
december2022 - A5
december2022 - Common diagnostics and trends in hybrid and electric vehicles
december2022 - A7
december2022 - Diagnosing faults on modern vehicles
december2022 - A9
december2022 - The real cause of P0420/P0430 DTCs
december2022 - A11
december2022 - How diagnostic tools cut through the ADAS confusion
december2022 - A13
december2022 - A14
december2022 - A15
december2022 - When the tools become the tutor
december2022 - A17
december2022 - A18
december2022 - A19
december2022 - A20
december2022 - Diagnostic products
december2022 - A22
december2022 - A23
december2022 - A24
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