Part 5 - The Issue

With the module now open, one can get to work with a multimeter set to measure continuity (this is often on the diode test setting; however, in the case of my multimeters, it is combined on the lowest resistance range instead). The first thing to do is to measure continuity from the 'plug' of the TPS module to the switch contacts. The centre pin of the plug is a common which is shared between both switches, the outer pins are unique to each switch. Make a note (mental or otherwise) of which pin on the plug shows continuity to which pin on the switch.

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Next, place the multimeter (still set to continuity) across each switch, ensuring that the central 'cam' that actuates the switches is in a neutral position (i.e. neither switch is closed). Both should read as an open circuit (no continuity). Next, actuate each switch in turn - actuating by hand is sufficient, the central 'cam' does not need to be used for this. When each switch is closed, it should show continuity across its contacts.

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Obviously, if one switch is constantly or never making continuity, that is a clear problem with the switch itself. The grey microswitch may or may not be removable. If it is then it can likely be replaced with a similarly-sized SPST, NO microswitch. Mechanical adaptation may be required to get it to actuate at the correct position, however. The copper strips are precisely that and the issue should be more easily visible if they are damaged.

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The final and most important test is to combine the above two steps: measure the continuity at the TPS 'plug' contacts, instead of directly across the switch. Measure continuity from left-most pin to centre pin, and then from right-most pin to centre pin. On each test, make sure to test both with the switch pressed and not pressed. Here is where I found my issue.