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Being Automotive Technicians today, we know that there are many sensors and modules now that use only 5 volts. It is so the vehicle has a consistent voltage reference to refer to. They control MAP Sensors, Throttle Position Sensors, Camshaft and Crank sensors, and much more. We have been getting many calls asking if any of our Power Probes can adjust the voltage output to 5 volts. So, we listened and are introducing a new 5 Volt Adapter accessory that works with all Power Probes, that limits the tip voltage from 12 to 5 volts.
You might be wondering how it works it’s quite simple just remove the Power Probe tip get your 5 Volt Adapter, plug it in where the tip would normally go, on top of your Power Probe then reconnect the tip. Most importantly, attach the aux ground cable to the tab on the right side of the 5 Volt Adapter. Now, when you actuate the rocker switch to supply positive power, you should see a red LED light, and it will light up to let you know you now have 5 volts at the tip of the tool no light no 5 volts. So, take, for instance, you have a 2015 Dodge Ram 1500 5.7 Hemi with a crank no start problem, first, check the code with a scan tool and see if you can see an RPM signal from the CKP sensor in the data. If the scan tool is reading an RPM signal, the sensor circuit is likely working, if the scan tool is not reading an RPM signal while cranking, there is likely a problem with the circuit that needs further testing.
The connector to the sensor has three wires – one is a reference power supply of 5 volts, one is the CKP signal output to the PCM, and the other is the CKP sensor ground. When you back probe the sensor ground you should get 0.0 Volts, if it does then that means it is working correctly on the ground side. Next back probe the Vref wire to the sensor and check your reading, you should see 5 volts, if not the PCM may have a problem with the 5 Volt Vref circuit. You can now add 5 volts to the sensor and check to see if the CKP sensor is responding as it should. If the Red LED on the 5 Volt Adapter goes dim when connected to the sensor or circuit that indicates that there is a short somewhere on the circuit. Since this 5-volt reference circuit also controls many other sensors the problem may be with the wiring or a different sensor. When looking at a wiring diagram for the vehicle, you can see that the Camshaft position sensor and wiring are also tied to the same 5-volt reference circuit. Since the PCM is controlling all the ground and signal we would then disconnect the Camshaft position sensor. By back probing the sensor and applying 5 volts to the 5V terminal on the sensor we find that the Red LED on the 5 Volt Adapter is back on the 5 volts comes up on the Power Probe. By performing a visual inspection we found that the CMP sensor circuit wire harness has been rubbing against the engine block causing a short to ground in the circuit. Now to just repair the CMP wiring and clear the codes to verify the repair and test drive the vehicle. Check out this 5 Volt Reference tool video we made. Our part number is PPT5VA01CS and will be available October 15, 2017, from your local tool Dealer! 5 Volt Reference Adapter