Scanmaster 2 Scantool

by Modern Musclecar

This is the most exciting products that we have come up with in a long time.  Actually, Bruce gets the credit for this one. One day he and I were tuning a customer's car. Bruce had a knock detector on his dash and every time he would get on this car, the lights would flash and the buzzer would buzz. We half expected the motor to let go so we took it back to the shop to get the OTC and the Turbolink with a scan tool hooked up. Even though the box on the dash was going crazy, both scan tools were saying zero knock. Even after putting race gas in the car and turning down the boost so we were sure we weren't knocking, the box was still making noise. We changed to our knock detector and even though it was better, it still didn't agree with the scan tools. This is when Bruce said, "Why can't we build a knock detector that shows degrees of knock on a readout instead of these silly lights?". This hit me like a ton of bricks and I realized he was right, we were doing this all wrong. Once I started thinking about it, I figured we could make something that shows knock, but O2 volts and TPS as well. This is when the Scanmaster was born. This completely self-contained box is about the size of a small radar detector or a pack of cigarettes and hooks up to the ALDL connector under the dash and mounts on top of the radio or dash. This unit comes complete with all hookups and instructions for tuning your car with it.

- It displays O2 volts so you can tell if your car is running rich or lean.
- Displays knock from the computer so you know for sure if your car is detonating.
- Has a recall button so at the end of a run you can recall the lowest O2 (lean mixture), highest knock retard, and the MPH as when they append so you know if it's on the launch or through the traps.
- With the engine off and key on, the Scanmaster displays the TPS voltage making it easier than ever to tune your car to its full potential.
- It can also display MAF, block learn, coolant and air temperatures, trouble codes, and more.

PLEASE NOTE: The Scanmaster does NOT require special chips!


 On initial key-on, DP6 will flash quickly as the Scanmaster synchronizes to the serial data stream.  The software version will be displayed on the left side.


Waiting Mode

 Once the Scanmaster has synchronized with the ECM, the display will change to “--- ---“.  During this time DP1 flashing indicates normal update mode (slow) or DP2 flashing indicates TURBO update mode (fast).


Run Mode

 When the engine is started the Scanmaster will enter RUN MODE and will display O2 milivolts (exhaust oxygen sensor) on the left display and Retard Degrees (detonation level) on the right display.  If Turbo update mode is selected, (requires special ECM chip) then the display will update twice per second (triple speed).


Expanded Modes

Pressing the MODES button selects expanded modes for display.  The data available for display depends on the chip installed in the ECM.  Refer to the Expanded modes reference for details.


Record Mode

While in RUN MODE if the TPS voltage exceeds 3.00 volts the Scanmaster will change the RECORD MODE.  In RECORD MODE the highest Retard reading and the lowest O2 Milivolt reading are stored in memory.  RECORD MODE is indicated by DP3 on.  The stored readings can be recalled at any time before the engine is turned off.  (See RECALL MODE).  Pressing the RECALL button while recording will erase any readings currently in memory.  This is used to delete ‘false knock’ from memory while racing.  Note:  RECORD MODE begins after 1 second delay (DP3 blinks).


Recall Mode

While in RUN MODE, pressing the RECALL button changes the Scanmaster to RECALL MODE.  In this mode, any previously recorded O2 and Retard readings will be displayed and DP3 will flash quickly.  Turning the engine off erases stored reading!  Pressing the MODE button while holding the RECALL button will display the speeds (MPH) of the recorded values.




  1. Disconnect the battery negative cable under the hood.
  2. Mount the Scanmaster inside the car on/under the dashboard radio pod or wherever is convenient.
  3. Extend and connect the BLACK wire to a ‘good’ ground.
  4. Extend and connect the RED wire to a fused power source, “IGN” terminal in fuse box is a good location.
  5. Connect the WHITE wire to the Serial Data signal.  The Serial Data is located at the ALDL connector under the dashboard the left of the radio pod.  Either use a .125” blade spade connector on the GREEN wire and insert into pin E of the ALDL connector; or use a crimp-loc connector and splice into the Orange Serial Data wire on the back of the ALDL connector.
  6. Reconnect the battery and test the Scanmaster.




The following is a method of tuning that I have been very successful with. You must be aware, however, that racing and getting maximum power from your car puts a huge strain on parts and you may have some type of failure.  Modern Musclecar will not be responsible for damage to any car that might be caused by improper use of this information.

We will be dealing with O2 voltage and the dreaded knock when tuning with the Scanmaster.  O2 voltage gives us an idea of Air/Fuel ratio.  The higher the number the richer the mixture.  Most cars run the best with an O2 of .750 to .770 Millivolts.  This is only a baseline and your car might like to be a little leaner (lower number) or richer (higher number) but this should get you in the ball park.  The readings you get will only be as good as your O2 sensor.  We do not recommend “heated O2’s” as we have found them to go bad without giving a code and giving a bad reading.  Leaner is meaner, the leaner you go, without knock, usually the faster you will go.  Beware, if you go too lean you will break something.  The following is a simple system for dialing in your car, without breaking parts.  Remember always tune for MPH, ET is only as good as your launch, you may tune up the car and make more HP causing tire spin that slows down the ET.  As long as the MPH is going up, you should be going in the right direction.


  1. Set the TPS.  .42 to .46 at idle and 4.6 to 4.9 at WOT is where you want to be. 
  2. Make a baseline pass.  Keep a notebook of fuel pressure setting, boost level, and Scanmaster readings in high gear.
  3. As long as the O2 is above the target (.750) raise the boost as high as you dare for the type of gas and head gaskets you are using.  Watch the knock retard, if you see it go up you need more fuel or octane.  A few degrees on the shift is OK as long as it goes away in the next couple frames.  If you see a lot of knock that is not going away or getting worse, take your foot off the gas.  You can always make another pass.
  4. Once you get the boost level to what you feel is max, (without knock) check the O2, if you are above the target start turning the fuel pressure down at 2 pound steps until the car starts to knock or stops going faster.  If the car starts to slow down go back up on fuel pressure and double check.
  5. Keep notes on all your passes.  Temperature and barometric pressure make a difference in the way your car will run.  If you pay attention to what your car is telling you, you will both be much happier.
  6. Always make 2 runs to confirm results, if you see knock lift and go back to the last good settings and make another pass.  A few degrees of knock at the top end is OK.
  7. If you make a major change to your car all your data changes, raise the fuel pressure, lower the boost, and start over.

Hope you enjoy Scanmaster, if you need help please call us.


SCANMASTER V2.0 Release Notes. (Feb 1996)


The Scanmaster 2.0 now displays the Open-loop/Closed-loop status.  Decimal point DP5 (the decimal in the Knock Retard value) will blink when the engine is running in open loop.


A few notes regarding the displayed values for O2 and Knock retard.  These 2 values are not interpreted by all scan tools the same way.  In its current configuration the O2 value displayed is in agreement with OTC2000/4000 and Turbolink.  However, the Scanmaster knock retard values agree with Turbolink.  Both the OTC 2000 and 4000 display knock retard values significantly higher than Turbolink.  Scanmaster 2.0 can now be selected to display values to agree with the OTC reading; during the Power-up phase of Scanmaster operation (display shows 2.0 .) press the left button (MODE) (display will show 2.0 . .).  The knock retard values will now read the same as an OTC would show.  These differences do not affect the way the engine runs, the difference comes frome the way the ALDL data is interpreted.


Scanmaster 2.0 can be configured at the factory to permanently display knock retard values scaled to match the OTC displays.  Contact your distributor for details.





Making a Scanmaster portable -

Go to Radio Shack and by a cigarette lighter plug and wire the power and ground to it.  By a .125"(1/8") spade connector and put it on the signal wire so it could just be plugged into the proper slot on the ALDL connector.  This will make the whole unit easily removable and completely portable between cars.


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