Snap-On ScannerREAL 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

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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

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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

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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

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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

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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

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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

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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 Snap-On 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).

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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.

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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

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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.

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GM TEST METHODSMode 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

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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.

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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.

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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

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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

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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.

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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.

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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)

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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:

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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.

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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.

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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.)

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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.

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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 )

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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.

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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

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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.

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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.

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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)

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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

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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

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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

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

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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.

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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

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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

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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

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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

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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

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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

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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.

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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:

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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.