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July 2015 39 easier test point. Remember that old saying "work smarter not harder?" The crank-sensor wire travels to the PCM. The PCM itself is located behind the glove box and provides a very easy ac- cess test point (Figure 7). Now, it's always nice when the wire diagram and the pin connec- tors all match. But we've learned over the years that they are not al- ways right. And that was the case with this vehicle. Back probing the listed pins proved that neither the pin locations nor the wire colors matched what we had in reality. So, how were we going to find the right wires? Remember critical thinking? We knew that the cam signal would be a square wave and the crank signal was a sine wave. We just went looking for them. The car would sometimes run OK. So we got it to run and idle and then we simply back-probed each pin until we located both signals (Figure 8). With the lab scope connected and displaying both signals, we went for a test drive. At first, both signals were perfect and the car ran great (Figure 9). We went back to our shop, shut the engine off and tried to restart it. Now the sig- nals gave us the evidence we need- ed (Figure 10). Our crank signal remained steady and regular, while the cam signal clearly was erratic and would drop out. Needless to say, the engine did not start either. Our cam sensor is bad and needs replaced. On this engine, the cam sensor is mounted into a housing assem- bly that can be rotated to adjust the timing. And the OEM only sells it as a complete assembly. However, you can simply replace the sensor (Figure 11). We actually called three parts stores until we found one that had the sensor list- ed individually and not a part of the more expensive assembly. There is one 10mm bolt that holds it in place. It's a very easy replace- ment, and there is no adjustment to timing necessary. With the new cam sensor installed, we per- formed several cold starts and road tests and the problem was no longer there. Critical thinking and finding the evidence again led us to the problem. ■Duane Mariage owns Marco Automotive in Springfield, Mo. He is an adjunct automotive instructor at Ozarks Technical Community College and offers advice at realfixesrealfast.com Figure 8 Figure 9 Figure 10 Figure 11 Three Easy Steps to Ensure You Are Providing World-Class Brake Service There are three critical steps that you must have as part of your brake service to ensure it operates the way your customer expects. Your customer is going to compare how their brakes performed when they first purchased their vehicle to your brake service. So what's the differ- ence between your brake job and the brakes on a new vehicle? Simply stated, it is cleanliness and tolerance. The top three critical steps to a world-class brake service: 1. Cleanliness: Do not leave grease marks on rotor surfaces, brake pads, or anywhere it could end up on those surfaces. Wash your hands, wash the rotors and use clean gloves. 2. Lateral runout: If you machine or replace the rotor, you must ensure you have as close to zero lateral runout as possible. 3. Break in those pads: You have one chance to introduce the pad to the rotor. If the first two steps above aren't done correctly, then this step doesn't matter. Follow the pad manufacturer's recom- mended process. One chance is all you get to properly introduce the pad to the rotor. When done correctly with zero runout, your customer will know you did the job right. Advance Professional offers 99% brake coverage on cars and light- duty trucks on the road today. To learn more about Advance Professionalʼs full line of brakes, call your local Advance or CARQUEST delivery location. Circle No. 32 on Reader Card