Diagnostic System Check Instructions
The following is an overview of instructions for the general
information and 14 step System Verification included in the
Diagnostic System Check - Vehicle procedure.
Diagnostic Instructions
A link to
Strategy Based Diagnosis is provided as an overview on how a
technician should diagnose a vehicle.
A link to the Diagnostic System Check Instructions is provided.
This provides an overview of instructions and examples for the
general information and 14 step System Verification included in the
Diagnostic System Check - Vehicle procedure. The examples in this
document are intended to give the technician a general idea of what
the test step is referring to. They are not intended to list every
possible condition or situation.
Diagnostic Systems Check steps are listed by priority to guide
the technician to the appropriate diagnostic procedure to correct
the customer concern. There are many ways to determine the priority
of diagnosing a vehicle concern. Some faults can cause customer
perceived symptoms in areas unrelated to the fault. Using an
example from the System Check, after reading DTCs, the technician
is asked to verify there are no Electronic Control Unit Internal
Performance Faults present. It is important that any internal
performance issues are addressed prior to continuing through the
System Check. There is no benefit addressing other DTCs that could
be set due to an internal fault to a control module. If the fault
is present, performing the diagnostic procedure for that fault will
likely correct the customer perceived concern and possibly
eliminate other DTCs that may be set.
Not all steps of the Diagnostic System Check have to be
performed. The Diagnostic System Check tries to prioritize the test
steps with the highest priority faults first. The technician is
then lead to another document to do the actual diagnosis or repair.
The strategy is to repair higher level faults that may be the cause
of other system or component level symptoms. Additionally, the
Diagnostic System Check can only be used for a single fault at a
time. If additional faults are present, the technician must perform
the diagnostic system check for each concern until all customer
concerns are corrected.
Once a repair has been completed, General Motors diagnostic
strategy is to always have the technician verify that the customer
concern has been corrected. This is to prevent comebacks and to
ensure customer satisfaction with their dealership experience.
Therefore a link has been provided to
Diagnostic Repair Verification procedure for the technician to
verify the customer concern has been corrected.
There are some assumptions made when General Motors prepares
service information. They include the following areas which are
presumed to function as designed:
• |
The 12-volt battery is fully
charged. General Motors assumes the majority of vehicles brought in
for repair will be able to start and be driven into the service
stall. If the vehicle has a dead battery, it is slow cranking or
for any other reason the technician feels the customer concern may
be battery related, a link is provided to
Battery Inspection/Test . This procedure will guide the
technician through inspecting and verifying the battery functions
properly. |
• |
Fuses should not be open.
General Motors does not call out in diagnostic procedures to verify
a fuse. The technician is expected to find an open fuse when the
diagnostic test step states to check for an open circuit condition.
Therefore a link has been provided to
Power Distribution Schematics and
Electrical Center Identification Views for technicians to
reference power sources and fuse locations if they feel there may
be loss of power due to an open fuse condition. |
• |
Ground circuits are clean,
tight, and in the correct location. General Motors assumes that the
original ground circuits have not been compromised. The technician
is expected to find a poor ground connection when the diagnostic
test step states to test the ground circuit for an open/high
resistance. Therefore a link has been provided to
Ground Distribution Schematics and
Harness Routing Views for technicians to reference ground
locations and which ground circuits may be related to the customer
concern. |
• |
All connections/connectors are
fully seated. General Motors assumes that all connections are
properly installed. The technician is expected to find an open or
poor connection when the diagnostic test step asks to test the
circuit for an open/high resistance. Therefore a link has been
provided to
Component Connector End Views for technicians to reference
which connections may be related to the customer concern.
|
• |
There are no aftermarket
devices that affect the operation of the system. General Motors can
only author diagnostic and repair information for vehicle systems
and components that are original equipment or genuine GM
Accessories. Aftermarket equipment can negatively affect original
equipment operation and lead a technician's diagnosis of a concern
in the wrong direction. Therefore a link has been provided to
Checking Aftermarket Accessories that guides a technician
through the possible causes of vehicle problems related to
aftermarket accessories. |
• |
The scan tool powers up.
General Motors assumes that power is available at the Data Link
Connector and the scan tool will power on. Therefore a link has
been provided to
Scan Tool Does Not Power Up if the technician finds that the
scan tool does not power on. |
Diagnostic System Check
1. |
VERIFY CUSTOMER CONCERN-This
step is to obtain as much information as possible from the
customer. Are there aftermarket accessories on the vehicle? When
does the condition occur? Where does the condition occur? How long
does the condition last? How often does the condition occur? Review
the service history of the vehicle for previous repairs that could
help diagnose the current concern. |
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Now that the technician understands the customer concern, they
should validate the concern on the vehicle. In order to verify the
concern, the technician should be familiar with the normal
operation of the system and refer to the owner or service manual
for any information needed. Inspect the visible system components
for obvious damage or conditions that could cause the concern.
Conduct a thorough visual inspection. Detect unusual sounds or
odors. |
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The condition described by the customer may be normal. If the
technician finds the vehicle to operate normally, compare with
another like vehicle that is operating normally, under the same
conditions described by the customer. If this is the case, explain
your findings and the operation of the system to the customer. If
the customer is dissatisfied, submit a Field Product Report. |
2. |
BULLETIN SEARCH-By searching
for related bulletins, recall/field actions and preliminary
information documents, a procedure for a known field issue may
resolve the customer concern with little or no diagnosis necessary
saving the technician diagnostic time. |
3. |
MECHANICAL CONCERNS-This step
is designed to take the technician directly to a list of symptom
diagnostic procedures. The technician is asked to verify the
symptoms exhibited by the system are mechanical in nature and not
related to an electrical system, see some examples below. If the
technician feels the concern could be related to an electrical
system, they should continue through the Diagnostic System Check to
verify the electrical functionality of vehicle. If the technician
feels the concern is exclusively related to a mechanical system, a
link to
Symptoms - Vehicle is provided to select the appropriate
symptom diagnostic procedure for the customer concern. |
|
• |
Brake noise or diagnosing
irregular pad wear |
|
• |
Engine or transmission fluid
leak diagnosis |
|
• |
Manual window or door lock
diagnosis |
|
• |
Vehicle vibration
diagnosis |
|
• |
Exhaust noise or leak
diagnosis |
4. |
VEHICLE POWER UP
VERIFICATION-The technician is asked in this step to turn the
ignition key ON and verify that the vehicle powers up. The
technician should look for clues that multiple vehicle systems are
receiving vehicle powermode messages, such as the cluster waking
up, the radio powers on, the HVAC blower is operational, windshield
wipers turn on, etc, with the key ON. This would be a rare
condition as both the powermode master and back-up powermode master
would have to be inoperable, however, if the vehicle does not power
up, a link to
Power Mode Mismatch is provided. |
5. |
CONTROL MODULE COMMUNICATION
and DTC CHECK-The technician is asked in this step to record the
following three pieces of data on the Repair Order; any control
module that the scan tool determined is not communicating, any DTC
and symptom byte set current or history, and the control module
that has set the DTC. |
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This is considered a setup step for the rest of the Diagnostic
System Check. The technician is not expected to do anything other
than record the three pieces of data provided by the scan tool on
the Repair Order. This provides the information needed to complete
the rest of the diagnostic system check. |
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To complete this step, the technician is asked to utilize the
scan tool function called Vehicle DTC Information located in
Vehicle Control Systems. This function will query every possible
control module on the vehicle requesting all DTCs. During the DTC
query, the scan tool will try to establish communication with each
control module. If the scan tool can communicate with the control
module during the DTC request, it will display PRESENT and provide
the number of DTCs set in the control module. If the scan tool
cannot communicate with a control module, it will only display NOT
COMMUNICATING. Since the scan tool cannot determine if a given
control module should be present or not, the technician is asked in
a future step to verify that the vehicle was not built with control
modules listed as NOT COMMUNICATING. |
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If the scan tool cannot establish communications with ALL of
the vehicles control modules, a link to
Data Link References is provided. A faulty control module or
fault with the serial data circuit can cause no communication with
all of the control modules on the vehicle. If any control module
communicates on the serial data circuit, continue through the
Diagnostic System check, as a future step will address any specific
non communicating or group of non communicating control
modules. |
|
Once the scan tool has completed the routine, the technician
should review each control module that has set a DTC and document
them on the Repair Order. When reviewing the DTCs, the technician
should take notice if any DTCs are powertrain related, and if so,
navigate in the scan tool to the Powertrain area and utilize the
Capture Info function. This will upload any Freeze Frame/Failure
Records stored in the control module to the scan tool in case the
data is lost from the control module. As an example, if the
technician commands a Clear DTCs function on a powertrain
controller, all diagnostic information stored in the controller is
erased. This includes Freeze Frame/Failure Records and
Inspection/Maintenance System Status indicators, if required for
your region. |
6. |
CONTROL MODULE INTERNAL
PERFORMANCE FAULTS-The technician is asked to review the DTCs
recorded in step 5 and verify there are no control module internal
performance faults set current. This type of fault may be the cause
of other symptoms or DTCs displayed by the vehicle. By addressing
this fault first, the technician may find the other concerns are
resolved. The technician should always follow the diagnostic
procedure for these types of faults prior to replacing any control
module. If the technician finds a control module has an internal
performance fault, a link is provided to
Diagnostic Trouble Code (DTC) List - Vehicle to select the
appropriate DTC diagnostic procedure. |
|
• |
B1000 Electronic Control Unit
Performance |
|
• |
B101D ECU Hardware
Performance |
|
• |
C0550 Electronic Control Unit
Performance |
|
• |
C056D ECU Hardware
Performance |
|
• |
C0570 Auxiliary Electronic
Control Unit Performance |
|
• |
P0606 Control Module Internal
Performance |
|
• |
P0607 Control Module
Performance |
7. |
CONTROL MODULE COMMUNICATION
VERIFICATION-This step is used to ensure the control modules that
are NOT COMMUNICATING were not built on the vehicle. To understand
if the vehicle was built with that option, we provide a link to the
Data Link References document where Regular Production Options
(RPOs) are listed next to ECU names and can be compared to those
the vehicle was built with. If the technician determines that a
control that is NOT COMMUNICATING should be present, the technician
is asked to follow the appropriate diagnostic procedure listed in
the
Data Link References document. |
8. |
COMMUNICATION and POWERMODE
FAULTS-This step is asking the technician to look for communication
DTCs or DTCs related to control modules powering up based on power
mode, communication enable or wake-up circuits. See in the below
table some examples of the DTCs the technician should diagnose
prior to continuing through the Diagnostic System Check. The
technician should review the list of DTCs recorded in step 4 and
verify that none of these type of DTCs are present. If so, the
technician is referred to the
Diagnostic Trouble Code (DTC) List - Vehicle to select the
appropriate DTC diagnostic procedure. |
|
• |
U0140 Lost Communication With
Body Control Module |
|
• |
U0164 Lost Communication With
HVAC Control Module |
|
• |
U0170 Lost Communication With
Passenger Presence Detection Module |
|
• |
U0402 Invalid Data Received
From Transmission Control Module |
|
• |
U0452 Invalid Data Received
From Inflatable Restraint Sensing and Diagnostic Module
|
|
• |
U1814 Powertrain High Speed
Communication Enable Circuit |
|
• |
B1428 Ignition Switched Power
Run/Crank Relay Circuit |
|
• |
B137B Accessory Power Module
Wake Up Circuit |
|
• |
C0897 Control Module Power
Moding |
|
• |
P2536 Ignition Accessory
Switch Circuit |
9. |
POWER MODE VERIFICATION-This
step verifies the Power Mode Master is receiving the proper output
state of the ignition switch. The technician should use the main
power mode input, this being either the ignition key or, on
vehicles equipped with Passive Entry Passive Start, the push button
switch. The test should not be performed using a key fob, if the
MIL is illuminated the powertrain controller may disable this
input. The technician is asked to perform the test with the driver
door open. This ensures the retained accessory power mode is
inactive during this test which could result in different scan tool
readings. The technician is only asked to verify the current Power
Mode parameter in the power mode data display list. If the
parameter does not match the actual ignition switch position, a
link is provided to perform the
Power Mode Mismatch diagnostic procedure. |
10. |
ENGINE CRANK and RUN
VERIFICATION-Here the technician is asked to verify that the engine
cranks and runs. The technician should use the main power mode
input, this being either the ignition key or, on vehicles equipped
with Passive Entry Passive Start, the push button switch, to
complete this step. The test should not be performed using a key
fob, if the MIL is illuminated the powertrain controller may
disable this input. The technician should know at this point
whether the engine cranks and runs without having to actually
performing this test step. One of the follow has probably already
occurred and this step can be skipped: The technician drove the
vehicle into the stall or verified when checking the Crank and Run
parameter in step 8. If the technician has not already somehow
verified the engine cranks in previous steps, the technician should
perform this test step. Regardless of how this step was performed,
if the engine does not crank, a link is provided to
Engine Does Not Crank or if the engine cranks but does not run,
a link is provided to
Engine Cranks But Does Not Run for the technician to choose the
correct diagnostic procedure for the actual engine application
being used. |
11. |
REMAINING DTC REVIEW-Here the
technician is asked to review any remaining DTCs that were not
addressed in previous steps. The technician is asked first to
verify there are no control module supply voltage, system voltage
or 5V circuit DTCs present. Control modules, systems or components
with insufficient or zero voltage can cause one or multiple
symptoms to exist on the vehicle. Control module voltage issues
could also be the cause of failures during a programming event. The
technician should correct voltage issues prior to addressing any
programming or configuration DTCs. The technician should then check
for any ECU programming, setup or configuration DTCs. By
programming software or configuring a control module, the
technician could correct the customer concern unobtrusively. The
remaining DTCs, which are usually specific system or component
faults, are diagnosed last. They can include ECU input and output
circuit DTCs or individual circuit faults that usually cause single
symptoms or failure modes on the vehicle and can be fixed following
the proper DTC diagnostic procedure. In general, the technician
should think about what DTCs or faults could be caused by another
DTC or fault. A failed sensor may set a component DTC and then the
system may set a DTC indicating the system cannot operate properly.
By correcting the sensor fault, the system may now operate properly
and the system level DTC will transition to history. Refer to the
examples within each category below to understand the differences
between these DTCs. If DTCs of these type are current, the
technician is referred to
Diagnostic Trouble Code (DTC) List - Vehicle to choose the
correct DTC diagnostic procedure. |
• |
B1325 Device Power 1 Circuit |
• |
C0875 Device Voltage Reference Input 2 Circuit |
• |
C1001 Adaptive Cruise Control Indicators Supply Voltage
Circuit |
• |
P0641 5-Volt Reference Circuit |
• |
P0787 Downshift Timing Solenoid Control Circuit Low
Voltage |
|
11.2 |
Programming, Setup,
Configuration or Software Performance DTCs |
• |
B3943 Steering Column Lock has Not Learned Column Integration
Module |
• |
B101E ECU Software Performance |
• |
B1019 System Configuration Error |
• |
C0558 Calibration Data Not Programmed |
• |
P0630 VIN Not Programmed or Mismatched - Powertrain Control
Module (PCM) |
|
11.3 |
Component related DTCs
|
• |
B0013 Driver Frontal Deployment Loop Stage 2 |
• |
B0163 Passenger Compartment Temp Sensor Circuit |
• |
C0045 Left Rear Wheel Speed Sensor Circuit |
• |
P0565 Cruise Control Switch Circuit |
• |
P0751 1-2 Shift Solenoid (SS) Valve Performance |
• |
B1010 System Sensors Data Mismatch |
• |
C0176 System Thermal Error |
• |
C0561 System Disabled Information Stored |
• |
P1564 Vehicle Acceleration Too High - Cruise Control
Disabled |
• |
P1625 Transmission Control Module (TCM) System Reset |
|
11.5 |
Any other remaining DTCs-The
technician should diagnose and correct any other DTCs that are left
that were not from the categories above. |
12. |
EMISSION RELATED
INSPECTION/MAINTENANCE TESTING CONCERNS-Several regions require
that a vehicle pass on-board diagnostic system tests and the
inspection/maintenance emission tests in order to renew license
plates or vehicle registration. This is accomplished by viewing the
Inspection/Maintenance System Status display on a scan tool. Using
a scan tool, the technician can observe the Inspection/Maintenance
System Status in order to verify that the vehicle meets the
criteria that comply with the local area requirements. If
inspection and maintenance checks are required in your region, and
the customer concern is related to not passing an
Inspection/Maintenance test, a link is provided to
Inspection/Maintenance System Check where the technician can
choose the appropriate Inspection/Maintenance System Check for the
actual engine application being used. |
13. |
SYMPTOM DIAGNOSIS-At this
step, the diagnostics are assuming that the only information the
technician has available to diagnose the customer concern are
symptoms of a problem. There are no DTCs set current or history.
There may be a Driver Information Center display message or a
system indicator to aid in identifying the root cause. The
technician should evaluate the symptoms and conditions described by
the customer and perform the symptoms diagnostics for the area of
customer concern. A link is provided to
Symptoms - Vehicle which contains a list of all symptoms
related to this service manual publication. |
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