October 2020

OCTOBER 2020 AFTERMARKET 23 www.aftermarketonline.net purchased the VCM2 interface so this seemed the ideal time to put it to the test and get to grips with it. I am familiar with several if the other manufacturer’s tools and portals but this one was new to me so I enlisted the help of my good friend and fellow Top Tech Winner of 2019 – Neil Currie. He remotely demonstrated how to use the portal and where to find the information. The information was limited in this instance and all we could find was a bulletin relating to the wastegate actuator. The symptom and one of the DTCs matched but this had already been replaced, twice, so it was time for some testing. The fault codes suggested that it wasn’t boost pressure- related, more the position of the actuator being incorrect. A thorough visual inspection showed us that it was a simple electro/vacuum controlled wastegate system consisting of a wastegate vacuum actuator with built in 3 wire position sensor, vacuum solenoid control valve, vacuum pump, the engine computer (PCM) and the wiring and pipework to connect it all. With a vacuum gauge I checked the vacuum to the solenoid valve which was good and the controlled vacuum on the other side which was also good. I manually applied vacuum to the actuator with a hand pump which proved there was no leak and that it moved freely from min to max stops. The serial (live) data allowed us to see the command or duty as a percentage for the solenoid valve and the actual position on the sensor in volts. This confirmed that it was a conventional 5-volt position sensor with a 5 volt supply and ground from the PCM and a signal wire back to the PCM which typically would range from between 0.5 – 4.5 volts. It also allowed us to monitor the command and the actual position the point it faulted. What I could see is that when the fault occurred the command went to zero and the position voltage went low which in turn fully opens the wastegate thus reducing/limiting boost pressure. Did the command stop, which caused the solenoid valve to stop applying vacuum and exhaust the diaphragm to atmosphere? Or did the PCM see an abnormality in the position and decide to switch the command to zero? There is always a delay in serial data and the refresh rate is not always fast enough to capture a glitch or see which of the two lines of data changed first. Electrical We can’t trust the live data but we can trust the oscilloscope so I set it up to monitor the electrical side. I did this in three stages: Stage 1: All three wires at the position sensor. Firstly, I monitored the 5-volt supply and ground at the sensor and then the signal wire at the sensor and back at the PCM and watched to see what happened at the point of fault. There was no abnormality in the 5-volt supply or the ground and both signal wire readings were identical. Stage 2: The solenoid valve which has just two wires. One is a 12-volt supply and the other is the switched ground which is turned on and off at a high frequency by the PCM. This is called a duty cycle. The longer it is on for the more vacuum is applied to the diaphragm and the longer it is off the ore of that vacuum is vented to atmosphere. At the solenoid I monitored the 12 volts supply which is nominal battery voltage (NBV) and the PCM-switched ground. During the off period it shows battery voltage (NBV) and during the on period it shows 0 volts. Both readings were what we expected to see. We could have added a third measurement here and monitored the current which would tell us more about the actual internal movements of the solenoid but what I saw in Stage 3 showed this wasn’t necessary. Stage 3: I monitored the Solenoid Duty and the position sensor signal. The vehicle was run and made to fault again and this time we could see exactly what happened first; the cause and the symptom. Fig.1 shows that the command/duty is suddenly switched off and the position signal starts to fall shortly after. So where next? The above tests may sound long-winded but in fact took no more than 20 minutes as accessibility was easy. Again with the help of Neil I connected the Ford diagnostic tool and logged into the FDRS online software. We looked through the functions and saw that there was a relearn function for the position sensor. Thinking I may have struck gold, I downloaded and ran the function which sadly once again made no difference. I was confident I had tested everything correctly. What was left? Two key parts had been replaced and eliminated from the investigation. The wiring and connections were confirmed to be good. That only left the PCM itself or the software within it. The power of networking is great and once again I conferred with Neil who agreed with my thoughts and process. Back on FDRS he demonstrated how to check when the software was last updated and also how to run a software update. With battery support connected I followed the on-screen prompts until the new calibration file was fully installed. With the RPM raised for a longer period of time the fault did not reoccur. An extended road test (See Fig.2) confirmed all was good. Fig.3 demonstrates the system in correct operation. You can see how when the required boost pressure is achieved the PCM adjusts the duty cycle to reduce the vacuum and open the wastegate in order to reduce and regulate boost pressure. What have I taken away from this job? It begs a question; at what point in the diagnostic process do you attempt a software update? Maybe I could have tried this earlier on in the process. My experience with other manufacturers has shown me that normally if there is a software update it is to fix a known fault or to alter certain parameters to account for wear and there will be a bulletin for it. I’m sure I am not the first person to see this fault but even with help I couldn’t find a technical service bulletin for it and clearly neither did the technician in the Ford dealership. I am happy though. The car is fixed, I got paid and I know next time I will be reaching for that OEM tool and information much quicker, and confidence to use it! Fig. 3