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					Snap-On Scanner
REAL WORLD DIAGNOSTICS

General Navigation ( Controls )
 Three controls provide ALL scanner

operation
 Thumbwheel – navigates from operation to

operation  YES (Y) Button  NO (N) Button

YES Button
The general uses of the YES (Y) button are:
 Select a menu entry shown by the cursor >  Advance (continue) through test routines

and other operating programs  Choose YES when a yes or no choice is given

YES Button cont
 Capture and hold a single frame of data in a

data-viewing mode
 When armed, trigger a movie recording  Change the thumbwheel scrolling operation

when you are reviewing a movie

NO Button
The general uses of the NO (N) button are:
 Reverse a step or exit from any menu or

program
 Return to the previous menu or an EXIT

options menu

NO Button cont
 Continue to back out to the next higher

menu until reaching the Main Menu
 Abort a program in process  Choose NO when a yes or no choice is

given

Quick ID Function
Press and hold the Quick ID button to apply power to the scanner from the internal 9 volt battery. Then enter vehicle identification before you connect the scanner to vehicle power. The scanner will display a vehicle connection message at the end of vehicle identification. Release the Quick ID button and connect to the vehicle as instructed on the display

Quick ID Function cont.
 The 9 volt battery located under the left

handgrip, also supplies power to the scanner to hold the following information:
 The last complete vehicle or system

identification entered into the scanner

Quick ID Function cont.
 Any data recorded as a movie or saved in

memory by holding a frame of data
 Most custom setup selections  Fixed line selections in the data display

until you change vehicle identification

Demonstration Program
 Almost all scan tools have internal demo

modes of operation. The Snap-On Scanner might have the best and most detailed you will ever see.
 These demo’s are built in to ALL of the

cartridges. USE THEM

Demonstration Program cont
 In order to use the engine demo program on

Ford and General Motors, enter D1M in this order when ID is entered.
 In order to use the engine demo program on

a Chrysler, just place the cursor on the demo selection in the Main Menu

Demonstration Program cont
 In order to use the ABS demo program on

Ford and General Motors, enter S1M in this order when ID is entered.
 In order to the ABS and other demo

programs ( Transmission, CCD etc.) on a Chrysler place the cursor on demo selection in the Main Menu.

Custom Setup
 LED Menu  Communication setup  English / Metric  Backlight

Custom Setup cont.
 LED MENU – Different vehicles use the

LED’s in specific ways. An example of this is GM vehicles use LED #1 to indicate open or close loop and LED #2 to indicate above or below 450mv being read by the oxygen sensor. LED’s #3 & #4 are programable

Custom Setup cont.
 LED MENU – On a Chrysler vehicle the

normal procedure would be for LED #1 to indicate rich or lean engine operation and LED #3 to indicate the whether or not the PCM is receiving a signal from the Knock sensor. LED’s #2 and #4 are not used. On other vehicles always look at custom setup to see what the LED’s are being used for.

Custom Setup
 COMMUNICATION SETUP – This mode

is used to match the baud rate of the SnapOn Scanner to any other device you are trying to communicate with (e.g. printer or software programs like Scan Gra-Fix you are using on your computer).

Custom Setup cont.
 ENGLISH / METRIC – This mode is used

for preference on seeing codes and data information in either English or Metric

Recording a MOVIE
 The Snap-On Scanner can record operating

data from any vehicle system that transmits information in the codes & data mode. This includes some transmission control computers, as well as engine control systems. This is sometimes referred to as snapshot or flight recorder capability. The recorded movie provides 75 to 100 frames of operating data for troubleshooting problems.

Recording a MOVIE cont.
 A recorded movie is very useful for solving

intermittent driveability problems. The movie is armed to record from the codes & data exit menu triggered by pressing Y while reviewing codes & data. A movie stays in scanner memory until the movie in rearmed to record another movie or until vehicle identification is changed

Scan Gra-Fix

Scan Gra-Fix

General Motors
A typical GM Main Menu lets you select the following general functions:
 Codes and Data – This selection allows

you to read trouble codes and view information from the PCM

General Motors cont
 Functional Tests – This selection allows

you to use specific engine operating tests.
 Movie – This selection allows you the

ability to record the data while road testing the vehicle or while using the dyno.

General Motors cont
GM TEST METHODS
Mode Resistance across pins A & B Scanner Screen Open Infinite ( open circuit ) Codes & Data (normal) C & D and road test ______________________________________________________ Diagnostic 10 kilohms Codes & Data ______________________________________________________ Backup 3.9 kilohms Functional Test ______________________________________________________ Field Service 0 ohms (shorted) Functional Test

General Motors cont
OPEN or NORMAL MODE  When pins A & B are not connected, an open circuit (infinite resistance) exists between them. This is sometimes referred to as “road test” mode, the PCM operation is not altered for any special diagnostic condition.

General Motors cont
DIAGNOSTIC MODE  In the diagnostic mode, the scanner places a 10 kilohm resistive load across pins A and B. This pulls the voltage on pin B down to about 2.5 volts and “turns on” the data stream to the scanner. This mode may be called the “special” or the “10k” in some manuals.

General Motors cont
DIAGNOSTIC MODE cont  The 10 kilohm load also affects PCM and engine operation in one or more following ways  Bypasses internal clock or timer  Adds a calibrated amount of spark advance  Energizes air switching solenoid KOEO

General Motors cont
 either energizes or disables canister purge

solenoid  fixes idle speed, idle air counts and injection pulse width  changes EGR operation during some engine running conditions  forces an idle air count reset at part throttle  prevents new DTC’s from setting while the 10 kilohm load is present

General Motors cont
BACKUP MODE  The PCM of a fuel injected engine contains a backup program and lookup tables that control fuel metering in case of a major system failure. When operating in backup mode, the PCM is powered by the ignition feed circuit and relies only on the signals from the distributor (tach), TP sensor and ECT sensor.

General Motors cont
BACKUP MODE  This mode of operation is sometimes referred to as “limp-in” which allows the vehicle to be driven to a shop for repair. The vehicle will not run normally because of the inhibited fuel control and restricted spark advance. On some vehicles, the mode will “time-out” every 50 miles, but will restart again and continue to operate.

General Motors cont
BACKUP MODE  A 3.9 kilohm resistive load must be placed across pins A and B of the ALDL to engage the backup mode. This mode is sometimes referred to as “3.9k” mode. If the vehicle runs better is this mode suspect air intake and/or fuel metering signals to the PCM to be faulty (e.g. MAF sensor)

General Motors cont
FIELD SERVICE MODE  When pin B is shorted to pin A in the ALDL connector, the PCM enters the field service mode. The field service mode can be used for different purposes, which include:

General Motors cont
FIELD SERVICE MODE  KOEO the MIL will flash DTC’s. Field service also energizes PCM controlled solenoids, allowing you to check for proper solenoid operation and current draw. On some vehicles the ignition timing is set to a fixed degree of advance so you can check and adjust base timing.

General Motors cont
FIELD SERVICE MODE  When a fuel injected engine is running in field service mode, the MIL does not flash DTC’s, but it will continue to flash. It flashes rapidly, several times per second, when the engine is in open loop and slowly, about once per second, when the engine is in closed loop.

General Motors cont
 Custom Setup – This selection allows you

to tailor the Snap-On Scanner to your preferences (e.g.- metric or english, LED menu programming, baud rate communication for printing etc.)

General Motors cont
 Fast-Track Troubleshooting – This

selection will take you over to the Troubleshooter Diagnostic cartridge. You will find detailed diagnostic information for driveability problems with and without trouble codes, along with tests and repair procedures

Ford KOEO
 Key-on, engine-off test – This test displays

on-demand hard codes present with the ignition on, but the engine not running. These are usually electrical open and short circuits and must be serviced first,before any other codes.

Ford KOEO cont
 For EEC-IV systems, the key-on, engine off

test also displays continuous memory soft codes of intermittent faults from PCM memory. These memory codes should be serviced last, after any other hard codes

Ford KOER
 Key-on, engine running test – This test

displays on-demand hard codes present with the engine running. These should be serviced second, after any KOEO hard codes and before any memory codes. Most 1988 and later Ford vehicles will not perform a KOER test if any KOEO hard codes are present and uncorrected

Ford Wiggle Test
 The engine-off and engine-running wiggle

tests place the scanner and the PCM in a standby mode to indicate an intermittent problem caused by wiggling electrical harnesses. If a fault occurs during a wiggle test, it is recorded in the PCM memory as a soft intermittent code. The KOEO test must be repeated to read the code.

Ford Functional Tests
 Computed Timing – This test allows you to

check ignition timing with the engine running at a controlled idle speed and a fixed amount of timing advance ( 20 deg ) above base timing ( which is 10 deg )

Ford Functional Test cont
OUTPUT STATE TEST  This test allows you to switch discrete PCM signals to system actuators on/off so that you can test component operation directly with a voltmeter or lab scope. In this test, the throttle serves as a toggle switch to cycle all PCM controlled actuators.

Ford Functional Tests cont
CYLINDER BALANCE TESTING (SEFI)  This test checks the operation of sequential fuel injection systems by disabling individual fuel injectors according to the firing order and noting engine rpm changes for each cylinder. A one stage test was used on 1986 and some 1987, after that the three stage test was introduced.

Chrysler
FUNCTIONAL TESTS  Fuel Pressure Test  Read J2 Volts  CDR Tester  Engine Off Tests  Engine Running Tests

Chrysler cont.
 Fuel Pressure Test – This test lets you

energize the Chrysler auto shutdown relay and operate the electric fuel pump. This will pressurize the fuel rail or throttle body assembly so you can check fuel system pressure. The key thing to remember here is that the PCM will ignore the program of waiting for a reference signal to operate the pump.

Chrysler cont.
 READ J2 VOLTS – Circuit J2 or FJ2 on

Chrysler vehicles is the ignition supply circuit to the PCM. It runs from the battery, through the ignition switch and/or the ASD relay to the SMEC or SBEC connector. We all seem to realize how important the EEC Power relay is on a Ford vehicles, but fail to realize the ASD on a Chrysler is even more important because it also feeds the ignition coil.

Chrysler cont
 CDR TESTER – These tests are designed

for a technician who is familiar with Chrysler’s Diagnostic Readout (CDR) tester. In this mode, the Snap-On scanner operates exactly like a CDR tester or a Diagnostic Readout Box (DRB)

Chrysler cont.
ENGINE OFF TESTS – This mode allows you to run a series of tests from Chrysler service manuals. The tests follow this general order  A review of fault codes  A group of switch tests to check the operation of driver-controlled switches

Chrysler cont.
ENGINE OFF TESTS cont.  An Actuator Test Mode (ATM) to check the operation of actuators, such as fuel injectors, the coolant fan and relay, and others  A group of tests to check the operation of sensors, such as the oxygen sensor, throttle position sensor and others

Chrysler cont.
 Chrysler Fault Codes – it is very important

to remember to diagnose DTC’s in numerical order. Also, most Chrysler PCM’s will use bookends of 88 and 55 for fault code diagnostics, any number between these two are DTC’s. If only 88 and 55 and shown, this means the self diagnostic system is working and there are no DTC’s

Chrysler cont.
CHRYSLER SWITCH TESTS – It is extremely important on today’s vehicles to check for proper switch operation. With computer operation modes such as fuel deleanment and torque converter clutch operation depending on correct readings

Chrysler cont.
ACTUATOR TEST MODE (ATM) – This test allows you to check the operation of PCM controlled actuators by ignoring the normal input. This is a very valuable diagnostic tool if used properly. Example of this would be firing the ignition coil without the PCM seeing an engine reference signal.

Chrysler cont.
ACTUATOR TEST MODE cont.- these test include:  01- Ignition Coil  02- Fuel Injectors  03- Automatic Idle Speed (AIS) Motor  04- Radiator Fan Relay  05- A/C WOT Cutout Relay

Chrysler cont.
ACTUATOR TEST MODE cont.  06- Auto Shutdown Relay (ASD)  07- Canister Purge Solenoid  08- Shift Indicator Light  09- Alternator Field Circuit  10- Auto Trans Lockup Solenoid  11- EGR Solenoid

Chrysler cont.
You can probably to more diagnostics and resetting of adaptive memory on a Chrysler vehicle then any other vehicle. Memory resets include:  Code clearing  Adaptive fuel  Min throttle  Idle air control  Emission service reminder

Chrysler cont.
Other diagnostic usage of the Snap-On Scanner includes CCD system on 1988 and newer Chrysler vehicles, which include:  Automatic Transaxle  Body Computer  Serial Bus Traveler  Standalone Serial Bus Traveler

Chrysler cont.
CCD system:  Electronic Vehicle Information Center  Electronic Temperature and Compass  Electronic Instrument Cluster  Electromechanical Instrument Cluster  Engine Node  Air Suspension

Imported Vehicles
There are a lot of pre-OBD II imported vehicles that do not have communication connectors, but I find most techs don’t realize that the Snap-On Scanner could still be a very valuable diagnostic tool. Many times you can use manual entry mode, which simply means that you would still QUICK ID the vehicle and the scanner would tell you the method for extracting the codes.

Imported Vehicles cont.
Once you “pull the codes” you will find a complete list of possible codes for that vehicle on the scanner display, simply place the cursor next to the pulled codes number and mark it. Now enter the Troubleshooter cartridge and follow the diagnostic tree for the circuit problem. All this without a physical connection to the vehicle

Chrysler cont.
SENSOR VALUE TEST – Chrysler computer system is probably the best at working off of back-up programs. It is extremely important to check sensor value in this mode to see if the value in the codes and data is the correct value or a computer substituted value. REMEMBER, The value in sensor value test is the “REAL McCOY”

Serial Scan Data
A scan tool retrieving serial data reads the digital signals the PCM supplies. A scan tool doesn’t read raw analog signals, such as voltages, the sensors send and receive

Serial Scan Data cont
On board computers change all their analog inputs into digital inputs before using them. Analog signals, most often voltages, are the way sensors communicate with the PCM. The PCM converts these voltages to digital signals so it can use the information.

Serial Scan Data cont
The scan tool taps into the PCM while all this is going on and retrieves whatever information the PCM will let it take. The PCM makes the data available; the scan tool just interprets it and displays the readings

Using a Scan Tool
A scan tool might display data in a different way than it received that data. For example a scan tool may display the coolant temperature when you expect to see the coolant sensor’s voltage. There are two reasons for unexpected scan tool readings:

Using a Scan Tool cont
 The PCM could translate a reading into a

different measurement.
 The scan tool could translate the PCM’s

reading into a different measurement

Closing Comment
 Remember, a scan tool is just that – a tool.

It’s up to you to interpret the readings correctly. It is also important that you understand the diagnostic limitations of a scan tool. Even with all the information you can get from serial data, the scan tool still doesn’t diagnose problems for you.

Closing Comment cont
 Don’t wait for a vehicle to come in on a

hook to look at the scan tool data. LOOK AT GOOD VEHICLES. So you will know what “normal” readings should be.


				
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