Most repair orders start with a complaint that something is not working when a button is pressed, a knob is turned, or a lever is pulled. In the past, it was a simple question of resolving the power, ground, and control circuits. Most circuits were wired discreetly with switches, relays, and a lot of wiring. Modern vehicles use multiplexing to reduce the complexity of the wiring harness while adding new functions.
It works like this: when the driver hits this button for the windshield washer, it sends a signal to the module in the steering column. The signal is registered and transmitted to the body control module using a serial data bus. Another module under the hood will provide voltage to turn on the pump. It sounds like a diagnostic nightmare. It can be if you don’t have one of these. Let’s plug in.
In the menu, we can see the different modules on the vehicle. The one we are interested in is the body control module. When we access the module, we see a few options. To diagnose the switch, we will use the live data function. Scrolling down, you can see the data PID for the switch on the stalk. If we press the button, we see the output toggle between on and off as we push the switch. We have confirmed the switch works and the modules between the steering column and body are communicating. We can now select the module for the windshield wipers. The button we will press is for the special tests. From here, we can actuate the washer motor. Nothing is coming out of the nozzles.
The next test will be checking for power at the washer bottle and pump. With minimal disassembly and a high-quality scan tool, diagnosing the customer’s complaint in less time is possible. The best part is that the diagnosis is confirmed.
This same diagnostic approach can be used for other switches, actuators, and modules. The strategy and tool can be used for everything from an EV charger port door to a headlight bulb.
The Special Test menu also has some great functions that can help you diagnose a problem, finish a repair, and confirm the fix.
Let’s say you just replaced or reflashed the ECM. For most vehicles, the crankshaft position sensor must be relearned after the procedure. This is because there are slight variations from engine to engine that can influence the crankshaft’s signal pattern. The check engine light will stay on if the crankshaft position sensor is not relearned. Also, the misfire monitor will be disabled.
The special test menu has a function to relearn the sensor. For this vehicle, the Bosch ADS-X walks you through the entire process from start to finish. Special tests can include EVAP, ADAS and many others on the vehicle. All coverage in the Bosch ADS X tools is OE-licensed, tested and validated before it gets added to the scan tool. And with coverage updates added monthly, you can be assured you will have access to the vehicle and special tests you need, when you need it.
To check the coverage of the special tests BOSCH diagnostic tool, click on the link in the description below. The site will also tell you if the tool can read live data, erase codes and what systems are covered by the software. Special tests are always being added and refined by BOSCH for current subscribers. The ADS-X has a one-year enhanced subscription that includes access to Repair-Source, wiring diagrams and other diagnostic resources. These special tests are vital software tools that can help you diagnose and repair vehicles in less time.
This video is sponsored by Bosch.
