Diagnostic procedure
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Diagnostic procedure. Training for the future. Diagnostic Procedure. So, where do we start?. Training for the future. Diagnostic Procedure. Listen to the customer complaint. Listen to the car’s complaint. So, where do we start?. Loaded electrical light check. Carry out basic checks.

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Diagnostic procedure

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Diagnostic procedure

Diagnostic procedure

Training for the future


Diagnostic procedure

Diagnostic Procedure

So, where do we start?

Training for the future


Diagnostic procedure

Diagnostic Procedure

Listen to the customer complaint

Listen to the car’s complaint

So, where do we start?

Loaded electrical light check

Carry out basic checks

Check battery supplies

Whilst car running

Measure voltage

Post to post

14.2 v

DC voltage

AC voltage

must be less then 0.3 volts

Training for the future


Diagnostic procedure

Diagnostic Procedure

Listen to the customer complaint

Listen to the car’s complaint

So, where do we start?

Loaded electrical light check

Carry out basic checks

Check battery supplies

Check battery grounds

Disable car from start

Block

Measure voltage drop (whilst cranking)

Negative Post to …

All must be less then 0.3 volts

Chassis

Clamp

Training for the future


Diagnostic procedure

Diagnostic Procedure

Listen to the customer complaint

Listen to the car’s complaint

So, where do we start?

Loaded electrical light check

Carry out basic checks

Check battery supplies

Check battery grounds

Extract codes

Codes OBD I & OBD II

Inform customer

Obtain budget commitment

Training for the future


Diagnostic procedure

Diagnostic Procedure

Obtain technical information

Supplies

So, where do we start?

electronic control module

inputs

outputs

grounds

Keep customer informed of progress

Prepare invoice

Diagnostics

R and R

Inform customer of final budget

Training for the future


Diagnostic procedure

Diagnostic Procedure

Diagnostic tools!

Training for the future


Diagnostic procedure

Diagnostic Procedure

Scan tool

Understanding DTC - P0123

Diagnostic tools

PPowertrain

BBody

Code ID

CChassis

U Communication

0Generic

1 Manufacturer specific

1- 8Specific area of concern

Training for the future


Diagnostic procedure

Diagnostic Procedure

Oscilloscope

Diagnostic tools

So, you want to measure an injector pattern

Back emf

Supply Voltage

Pintle bounce

Ground

Injection Pulse width

Training for the future


Diagnostic procedure

Diagnostic Procedure

But, before one engages in diagnostic procedure, one mustunderstand how the system works and what the parameters ought to be (data list, waveforms,voltages, current, resistance etc).

And above all 'should the component fail - what will the symptom be?’

Training for the future


Diagnostic procedure

Diagnostic Procedure

Throttle control

How does the system work?

Conventional throttle control

TPS (input)

Throttle body

TPS input

Ecm controls output timing injection etc

electronic control module

AF input

Accelerator peddle

Cable controls butterfly

Training for the future


Diagnostic procedure

M

Diagnostic Procedure

Throttle control

How does the system work?

Electronic throttle control

TPS (feedback)

electronic control module

Electronic accelerator peddle

Ecm controls motor (butterfly)

Training for the future


Diagnostic procedure

Diagnostic Procedure

Sun-load sensor

How does the system work?

Single zone

Dual zone

Training for the future


Diagnostic procedure

Diagnostic Procedure

Catalytic converter

How does the system work?

+ volts

+ volts

time

time

Pre Cat Ox sensor

Post Cat Ox sensor

Catalytic converter

Training for the future


Diagnostic procedure

Diagnostic Procedure

Sensors

How does the system work?

+ volts

Magnetic

time

- volts

volts

Optical

time

volts

Hall Effect

time

Training for the future


Diagnostic procedure

Diagnostic Procedure

Current limiting

How does the system work?

No current limiting (ign coil)

Linear current limiting (ign coil)

Switched current limiting (injector)

Training for the future


Diagnostic procedure

+

-

+

-

Diagnostic Procedure

Differential amplifiers

electronic control module

Inverting and non inverting Inputs

How does the system work?

+ volts

time

electronic control module

+ volts

time

Training for the future


Diagnostic procedure

Diagnostic Procedure

TPS

Should this component fail what will the symptom be?

If there was a sudden drop in voltage?

tps

Training for the future


Diagnostic procedure

Diagnostic Procedure

Injector

Should this component fail what will the symptom be?

Good pattern at idle

Good pattern snap throttle

Good pattern back-off

Training for the future


Diagnostic procedure

Diagnostic Procedure

Trigger module

Should this component fail what will the symptom be?

Good current limiting

Uncontrolled oscillation

bad current limiting

Training for the future


Diagnostic procedure

Diagnostic Procedure

Ox Sensor

Should this component fail what will the symptom be?

Lazy Ox sensor

Bad earth

Snap throttle

Closed loop

Good Ox sensor

Training for the future


Diagnostic procedure

Diagnostic Procedure

Immobiliser

Should this component fail what will the symptom be?

Electronic key

Smart key reader

Body control unit

Electronic cont mod

Training for the future


Diagnostic procedure

Diagnostic Procedure

Should one of these components fail How will it relate to customer’s complaint?

Reading technical information

Supplies (DC & AC)

electronic control module

inputs

outputs

grounds

Training for the future


Diagnostic procedure

Diagnostic Procedure

Charging systems

Reading technical information

Engine running

Ignition ON

Ignition off

System shut down

Ignition off

Engine starts

Cranking

Training for the future


Diagnostic procedure

Diagnostic Procedure

Hard wired

What is CAN bus?

Non - CAN bus systems

ect

ecm

dashboard

tcm

(conventional system)

air con

other

Training for the future


Diagnostic procedure

Diagnostic Procedure

Sharing of information

Similar to a Fax machine

What is CAN bus?

Puts a message on the ‘BUS’

Other control units share information

It is NOT unilateral

ect

ecm

It is ‘Bidirectional’

dashboard

CAN bus systems

tcm

air con

other

Training for the future


Diagnostic procedure

Diagnostic Procedure

How to diagnose

What is CAN bus?

DTC

Myriad of DTC’s – which one would you tackle first?

Must decipher which control unit is ‘logging’ the DTC code

ecm

CAN bus systems

dashboard

tcm

air con

Training for the future


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