Installing the TechnoMotive Datalogger

NOTE! Please be certain to read about the possible side-effects of using the Datalogger found at the bottom of this document.

Before You Begin. Note that while the wires on both ends of the Datalogger are properly strain-reliefed, we highly recommend that you don't unplug either end by pulling on the cable. Also, since the diagnostic port is located above the driver's left foot, care should be take to insure the wire doesn't get tangled up with the driver. While tucking the wire behind the carpeting is expedient, it inevitably falls out. Any permanent or semi-permanent installation should use twist ties or Ty-Raps to keep the wire out of the driver's way.

Figure 1 - Locating the Diagnostic Port
  1. Locate the Diagnostic Port. On all 90-94 DSMs, the diagnostic port can be found next to the main fuse panel on the top left side of the driver's footwell. Figure 1 is from a 1990 DSM.

Figure 2 - The Diagnostic Port Exposed
  1. Remove the Diagnostic Port Cover. First remove the fuse block cover by lifting on the tab shown in Figure 1. Pull the black shroud cover up and over the side of the diagnostic port.

Figure 3 - Matching the Plug Notches
  1. Align the Diagnostic Plug. Be sure to match up the notches between the plug and the port before insertion. These are highlighted in Figure 3.

Figure 4 - Inserting the Plug
  1. Gently Set the Plug into the Port. As shown in Figure 4, insert the plug without applying any force. There might be a gap between the top board and the top of the plug at this point.

Figure 5 - Inserting the Plug all the way
  1. Press the Plug into the Port. Using your thumb and index finger, press down on the small nuts indicated by Figure 5. There should no longer be a gap between the top board and the top of the plug.

Figure 6 - Installing the Power Line
  1. Hook the Datalogger to Power. Now you must select an empty fuse holder to power the Datalogger. Figure 6 shows the available sockets on a 1990 DSM. Later models have fewer free fuses. You should consult a shop manual in order to make the best selection. Please note that one pin of the fuse socket will have power, and the other pin will not - you may have to try both of the pins. Since there is a powered circuit in the RS-232 connector shell of the Datalogger, you should pick a power source that is off when the engine is off. Fuse #2 and fuse #8 would be good choices (fuse #8 is populated in Figure 6 because this particular DSM's owner is using it for a high-powered headlight circuit). Fuse #13 and fuse #15 are connected to power at all times and are therefore less desirable choices for a permanent installation. Power is connected to fuse #15 in Figure 6 because this particular DSM's owner was doing a power drain test to see if the Datalogger would drain the battery. It seems to not be a problem as long as the car is run at least once per week. After a fuse is selected, the yellow power line should be tucked between the fuses so the cover can close.

Figure 7 - Finishing Up
  1. Cleanup. If you have tucked the power wire down, you should be able to easily close the fuse cover as shown in Figure 7. Do not attempt to pull the black diagnostic port cover over the Datalogger - it will not fit. Dress the cable so that it won't fall onto the the driver's left foot. You can use the black port cover to hold the cable up in a temporary installation. Then you can tuck the cable behind the carpeting, as shown in Figure 7. Now plug the other end of the cable into your laptop PC and you are done!

Possible Datalogger Side-Effects

There is a slight inconvenience in the way Mitsubishi designed their diagnostic system - all of the control modules in the car share the same pin for activating diagnostic mode. Since the Datalogger uses this diagnostic mode in order to gather data from the ECU, every unit in the car will be in diagnostic mode whenever the Datalogger is installed in the plug. This happens even if the Datalogger is not gathering data or is not connected to a laptop!

Being in diagnostic mode is not a problem for almost every module in the car. The ECU and the TCU (automatic-transmission computer) are designed to deliver data while the car is running. However, the ABS computer apparently is not. It seems that when the Datalogger is plugged into the port, the ABS computer shuts down and turns on the ABS light in the dashboard! You can get around this by either discconecting the ABS computer from the diagnostic line or installing a switch on that line so you can easily re-enable the ABS diagnostic mode in case you ever take it to the dealer for service. We hope to have information on how to do this in a future revision of this document.

There is another small problem that won't happen unless you are trying to set the engine timing. There are two diagnostic modes that you can put the ECU into without using a Datalogger. One of them is for setting the basic 5 degree engine timing - there is a connector in the engine bay for doing this. The other mode is for setting the basic idle speed - ground the connector in the engine bay and ground the pin in the diagnostic plug that puts the ECU into diagnostic mode. Have you guessed what the problem is yet? If the Datalogger is installed and you try to adjust engine timing by grounding the connector in the engine bay, you will actually be putting the ECU into basic idle speed mode instead. So just remember to remove the Datalogger before you try to set the timing.

©1998 Technomotive
July 19th, 1998