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Power Probe IV - Testing Fuel Injectors - Quick and Easy



By David Barden

If you have a car that won’t start or is misfiring, typically one of the first things to check is whether the fuel injectors are delivering fuel to the cylinders properly. Fuel injectors are essentially just electric solenoids that only provide fuel when they are commanded by the engine’s computer. 

injector testing PP4

As with any electronically controlled system, there are many things that can go wrong that could prevent the fuel injector from working. The coil windings inside the injectors themselves could be shorted or open, they need a good source of power, and they need a good grounding signal from the ECM/PCM that is the proper duration. Any open or shorted condition in the injector wiring could also keep an injector from firing and you need to be able to detect those also.

Fuel injector test



There are a variety of currently used techniques and tools that can test a fuel injector or injector circuitry; however it usually involves using multiple tools and tests to check every aspect of the injector circuit. Complete testing could take quite a bit of time.



One powerful, time-saving feature included in the Power Probe IV is the dedicated Fuel Injector mode that can quickly and easily test the entire injector circuit with one simple probe connection.Power Probe 4 

One screen displays all the information you need; the voltage supplied to the injector, the ECM ground switching voltage, the inductive kick voltage from the injector windings, and the injector on-time in milliseconds. The LEDs at the top of the display also blink and the speaker tone sounds every time the injector fires, letting you know if it is operating consistently. Everything a scope would tell you without using a scope. 

Check out the video to see the Power Probe IV’s Fuel Injector mode in operation and how quickly you can now diagnose injector circuits.  Watch the Video

Power Probe IV


By David Barden

It was a few years ago, but I distinctly remember the day I first learned about Power Probe.

One of our technicians bought a Power Probe from the tool truck and used it to quickly diagnose an unusual lighting problem.

Power Probe 3He was so excited about how well it worked; he called a few of us over to check it out. We all played around with the Power Probe for a couple of minutes, turning on fans, lights, the fuel pump and even starting the car by activating the starter relay.

The tool’s unique troubleshooting capabilities were obvious to everyone and within a month almost every technicians in the shop owned a Power Probe and the guys who didn’t were asking to borrow mine.

The Power Probe was always a valuable tool, but there were still plenty of tests where I had to go back to the toolbox to get out my multimeter. 

Power Probe has just released their most powerful version yet, the Power Probe IV, and let me tell you, my meter may never come out of the toolbox again!

Power Probe IV

The new Power Probe IV still provides power and ground to activate components, but it’s also packed with multimeter features.  It measures DC and AC voltage (up to 200 volts while displaying Min and Max), resistance (even on powered circuits) and can display Frequency and Pulse Width!

All these are done with one simple probe connection. No more two-handed testing or trying to find new ground connections throughout the car.

The Power Probe IV also has advanced features you won’t find in any multi-meter:

fuel injector testing
  • Fuel Injector Testing
  • ECM/PCM Driver Testing
  • ECT Mode (which works along with the ECT2000 Short and Open Finder)

I love the large, easy to read LCD display and menu buttons to easily scroll through the different functions. Its controls are easy to figure out and it takes very little time to learn how to use properly. I think just about any level mechanic could pick up one of these units and use it effectively.

The Power Probe IV really is one of the most useful and powerful electrical circuit testers I have ever used, and my DVOM is going to get very lonely.

Check out the Power Probe IV introduction video and let me know what you think!

  Watch the IV In Action

How to Properly Repair Automotive Wiring


By Dave Barden

What Causes Electrical Malfunctions?

chafed harness

The majority of vehicle electrical malfunctions are usually found to be problems with the electrical wiring itself.  Wiring and connectors are constantly exposed to severe conditions like high heat, harsh chemicals, repetitive movements, and vibrations.

Wiring harnesses are also vulnerable to abrasion, stress, corrosion, or collision damage. 

To fix the vehicle you can choose to either repair the damage or replace the damaged wire harness section entirely. However, replacing a wiring harness can be expensive and very time consuming to install.

If it's done correctly, repairing damaged wiring is perfectly acceptable and can save considerable money and labor.


What Makes a Good Wire Repair?

The key to a good wiring repair is having a clean solid mechanical connection before soldering the joint, and always use heat shrink insulation to protect your wire repair.

How Can I Learn How to Solder Wires?

Soldering is an invaluable skill to have and you can learn to solder by watching our How to Properly Repair Automotive Wiring Video, and be sure to download a copy of our Basic Electrical Soldering E-book, all completely free.

       Watch The Video

Soldering Tips.

  1. Be sure to remove all of the damaged wire section.
  2. Use the Micro Torch with the Hot Knife attachment to strip and prepare the wire ends for soldering.
  3. Make sure you have a clean solid mechanical connection before soldering.
  4. Use Rosin Core Solder when soldering wires, the flux deoxidizes and allows solder to penetrate into the wire strands.
  5. Once you have enough solder on the joint, let the solder harden before moving the wire.
  6. Use a heat shrink insulation tube that has a 3 to 1 shrink ratio.
  7. When heating shrink insulation, use the heat shield accessory in the Micro Torch Kit to protect the neighboring wires.



Expect the Unexpected! Differential Pressure Feedback Exhaust

by David Barden

Little Problems, Big Failures

It’s almost always a little problem, but little problems can cause big failures. This is something I used to preach regularly to technicians I was coaching or training. Like most of you, I’ve seen my share of catastrophic failures, but when the failure is traced back to the origin, it is almost always found to be a relatively tiny flaw that snowballed into a larger problem.

under hood fireLet me give you an example… In this case, we had a Crown Victoria that had a small under hood fire that appeared to start from the (DPFE) Differential Pressure Feedback Exhaust Sensor. This was a low mileage car that was less than a year old. I was sure this was something the factory reps would probably want to look into. I placed a call to our local Field Engineer and told the technician working on it not to repair the car until they had inspected it. They inspected the car, condemned the DPFE Sensor as the culprit, and repairs were authorized to replace the sensor and any fire damaged components. Parts were ordered, but I had that nagging feeling there was something else going on here.

Later that day, the technician approached me saying the Crown Vic will be ready to go after heDifferential Pressure Feedback Sensor clears a check engine light he found. That did not immediately seem unusual as I would imagine, with the sensor melted, there would likely be a Diagnostic Trouble Code registered. But I had a suspicion and asked him to let me know what he found. There were indeed codes related to the DPFE Sensor, but he also reported that he found a stored code P0306, cylinder # 6 misfire detected. After clearing the codes the P0306 did not immediately return and our first thought was that the two were unrelated. In the service bay the car appeared to run fine. We were about to return the car to the fleet, but I couldn’t stop thinking about that misfire code and how it could possibly fit into the engine fire. Then suddenly, it hit me! I asked the tech to put the car on the hoist and drop the exhaust. “I want to see the cats.” I told him as he glared at me with that look of “Why?”. As I suspected, after the exhaust was lowered, inspection of the catalytic showed the substrate melted and almost completely blocking exhaust flow.

This made perfect sense now! A misfiring cylinder #6 overheated the catalytic damaging the substrate, the increase in exhaust backpressure forced more exhaust pressure into the DPFE eventually melting the sensor and hoses, and then continuing to spew hot exhaust under the hood, causing the small fire. Further, when tracking down the misfire, the only fault found was that the plug wire was not fully engaged onto the spark plug. This also made sense. The weakness in firing the #6 cylinder did not show up until under a load.

So a little problem created a big failure. A simple loose spark plug wire connection, led to an engine fire that could have easily destroyed the entire car. This car was nearly returned to service after replacing only the damaged parts, which only would have led to a second DPFE failure, or possibly worse! Taking the time to think about why the sensor melted in the first place, led us to more part failures, and eventually the “root cause”, the loose plug wire that started it all.

Many times we get busy and rushed, but take the time to go one step further and think about what caused the part to fail. The pay-off is well worth it! It may prevent the replacement part from suffering a similar fate; avoiding an unnecessary comeback, and a potential unhappy customer.

When diagnosing a car’s electrical system, this type of troubleshooting can be especially valuable, i.e. don’t just replace that melted relay, find out why it overheated! Is the load failing and causing too much draw? Are there any voltage losses in the circuit that would increase the current through the circuit? What is the small problem causing the large failure? Ideally, the entire circuit should be tested for any other electrical issues before simply replacing parts. Power Probe’s circuit testers are the perfect tools for this type of testing. You can check for voltage drops, load test components, verify powers and grounds, and with the smart, easy to use Power Probe testers you can quickly and accurately find those “little problems” before they can cause “big failures.”

I’m sure you guys and gals out there under the hoods have your own similar stories, even an instance where a Power Probe tester helped in your diagnosis. We can all learn something from them, so please let us know!


  Learn New Techniques



Top Tech Jeff Everett A Oxnard College Automotive Student


describe the image & student worker Jeff Everett was hired by a Toyota dealership today. Jeff received his certificate this year and plans to continue on and complete is A.S Degree. We selected Jeff as out Top Tech this semester, he received the PowerProbe III Master Kit ( donated by Mr. Dan Romero from Power Probe ) at our end of the year BBQ. Please see attached photo.


Automotive instructor teaches electrical, using the Power Probe 111

Jeff Hiben, automotive instructor from Oxnard College, explains motors and wiring to students at the career day hosted by Blackstock Junior High School in Oxnard Tuesday. Students had the opportunity to ask questions to presenters and if the questions were strong enough, they received a raffle ticket.

Read more: 
- Oxnard College

Parasitic Draws and Ways to Tackle Them

By David Barden

parasitic drawWhy does my car battery die after sitting overnight in my driveway?  This is a common question heard from customers in almost every shop.  The battery could be nearing the end of its life, you left something on like your lights, or a component is causing a parasitic draw.  A parasitic draw can be defined as any electrical device that draws electric current when the ignition key is turned off.

All modern vehicles draw some power from the battery even when the vehicle is off. The vehicle needs a small amount of power to maintain memory in the PCM and to keep settings in things such as clocks, radios, etc. This low power draw is expected, and normally the amp draw is low enough that the vehicle can sit for long periods of time without problems. When other items are using more power than expected or not shutting down correctly, your battery will discharge faster than normal and in a worst case scenario; leave your vehicle with a dead battery.

A Parasitic Draw Test is used to measure how much power the vehicle is consuming when it is shut off, and determine if it's a normal amount or an excessive amount of current draw. This test is typically done by disconnecting one of the battery cables and placing a meter in series between the battery and cable to capture all current going into the vehicle.

Although you can measure the vehicle draw with an inductive amp pickup, due to the very low milliamp readings involved, the in-circuit testing method is desired (even using standard multi-meters) over using an inductive clamp due to the more accurate readings obtained. However, it can be risky connecting standard multi-meters in-line for current testing as they are usually limited to about 10Amps max and any unintentional load can blow expensive, hard-to-find meter fuses. The HOOK has the advantage of the Adjustable Circuit Breaker and up to 65 Amp current capacity so there is no danger to the circuit or the tool when using The HOOK in this case.

However, connecting the Power Probe Hook to measure parasitic draw is a little different than how you would usually connect a standard multi-meter. Since the Hook is always connected to the battery, it is just a matter of dis-connecting the negative cable, and then supplying ground through the Hook to complete the circuit.  Watch this video for proper testing and techniques for locating the specific circuit causing an excessive drain.

Click Here to Download the Fuse Charts

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