Just the 2 weeks wammers
Don't worry Spadgr, i think i understand what you are getting at.
Many have heard about diagnostic equipment and will appreciate that it can read and clear faults, but i guess you probably like many others want to know more of the nitty gritty of how that helps in real life situations and what else it does that can help in the fixing of any possible faults.
I hope i can oblige.
It's a bit of an open subject, as it really depends upon the nature of a fault, but i will try to take you through a few of the more regular real world scenereos.
In many cases faults can be stored where there is no true physical fault, due to a system wobbly or through temporary disconnection of something while working on the car. In some cases this can take a vehicle system off line.
These simply require the clearing of the fault code memory.
Next up is where a fault is caused due to a poor connection (possibly corrosion) somewhere or a faulty sensor or motor / actuator such as Irishrover describes. If the fault is permanent it will re log straight away and if intermittent it will still come back. It needs a human to physically find the cause and fix it. In many cases just the fault text itself is enough of an aid. IE Open circuit water temperature sensor (intermittent), could be an iffy sensor, faulty wiring or a corroded connector and with enough effort and checking and metering it is possible to find the fault.
However in trying to locate such a fault, the ability to see the actual value returned from the sensor in real time can be really helpful, as you can watch it while you wiggle connectors and wiring etc. In some cases monitoring the live data is the only way to see whats going wrong. We also provide a couple of capturing facilities such that data can be retro analysed or saved for later comparison.
Outputs can also be very handy. Suppose you have an electric window not working. The first question is, is it the switch (Input) or the motor (output) side. By conventional means you would have to pick between pulling the door or the switch pack apart. Sods law dictating you get it wrong most times. However on the BeCM you can see if the ECU is seeing the switch input or not and you can force the BeCM to directly drive the window to see if it works regardless of the switch input. There are near 100 inputs and outputs on the Becm alone.
In the specific case you mention (TPS) you cannot check it or physically adjust it any other way than with a manufacturer dedicated diagnostic system with live data values such as ours. In fact as far as i know, for this there is no other equipment availiable that provides this without costing 10 times more.
For anyone wanting to see exactly what capabilities are provided by our equipment on any system, we quite proudly publish this on line. (I say proudly because so many with much lesser capabilities just gloss over the important detail). If you go to our web shop, select MSV-2, then software and finally multi vehicle, you will get a long list of all the ECU's our system can cover. scroll down to the ECU of interest, In your case i am assuming EDC as the engine management of the 98 DSE you list in your profile. Then click on the more information button.
For the EDC, this will give you this page
https://www.blackbox-solutions.com/shop/help/SM007.html
If you scroll down to inputs, you will see that there are 3 pages of them, The one you are interested in is in the General section and reads
# Throttle pot volts: The current voltage output from the Throttle position Potentiometer. Should go below 0.8 volts when the pedal is released and above 3.3 volts when the pedal is depressed.
Armed with this information and the equipment with the capability to show you what values you are getting from your Throttle position sensor you can check it and physically adjust it to get the right values if needed.
No doubt you will also note the many other elements that can be checked on this system alone and in fact i have hardly scratched the surface on what is truly possible with our system and as any owner will testify, to attempt to do so would be a truly monumental task.