Tool Briefing 1 DUPLICATE THE CUSTOMERS CONCERN As always, the first step in diagnosing a vehicle is confirming the condition exists in the conditions the customer states the issue occurs. By doing this, you will also be able to confirm you have completely and correctly repaired the vehicle. 2 SCAN THE VEHICLE Scan the vehicle to check for any fault codes. Note any codes that are present as well as any freeze frame data. It is also a great idea to see if all the monitors have been completed and to check the results through Mode $06 in your scan tool to determine if any of the monitors are close to failing or if they are within the normal range. Monitors that are close to failing can assist you in diagnosing intermittent issues. You may also be able to use Mode $06 to detect which cylinder or cylinders are misfiring. Observing data PIDs such as coolant, intake air and fuel temperatures can give clues to possible issues. Coolant temps that are too high can be signs of internal engine issues that may cause symptoms similar to what was experienced. Fuel or air temp PIDs that are not normal can also assist in your diagnosis. As with any diagnosis, both short and long fuel trim values can contribute valuable clues to determine how the engine management system is adjusting the fuel mixture to the engine. 3 OBTAIN VEHICLE INFORMATION After confirming the issue exists and when it occurs, you are equipped with enough data to utilize your information resources, such as Mitchell 1 ProDemand, to determine if any TSBs are available. Since GDI implementation is relatively new, there are many relevant TSBs ranging from mechanical or electronic component replacement to reprogramming PCM strategies. An example of mechanical failure on some of the early VW GDI applications is the camshaft lobe that drove the high-pressure fuel pump would wear prematurely due to extra pressure from Circle 215 on card, or enter at www.VehicleServicePros.com OCTOBER 2016 PROFESSIONAL TOOL & EQUIPMENT NEWS 73 “e-inquiry” on VehicleServicePros.com the pump. The symptom of this is lowerthan expected fuel pressure on the highpressure side with the PCM commanding higher-than-normal pressure. The repair of this issue was to replace the camshaft and high-pressure pump. Another mechanical failure example includes the high-pressure pump leaking fuel into the crankcase. The symptom of a leaking pump is fuel in the crankcase. The TSB recommends replacing the pump and completing two successive oil changes to remove excess fuel from the crankcase. Using your vehicle information system can not only help you discover a common issue quickly, but also to determine the recommended repair for the failed component(s). 4 PERFORM ADDITIONAL DIAGNOSTIC TESTS Once you have determined if there are any DTCs and/or TSBs, it is time to utilize some other necessary tools. GDI systems require the low-pressure system be capable of delivering the correct volume of fuel at the correct pressure to the high-pressure pump. One of the first tests you should perform is a pressure and volume test on the low-pressure system. We use the Mityvac MV5545 fuel system tester to complete this test. This kit has a fuel pressure gauge as well as a flow meter to test the volume of fuel being delivered. Keep in mind it is necessary to use your scan tool to command the pump to operate at 100 percent. Due to the extremely high fuel pump pressure, GDI high-pressure tests cannot be performed with a mechanical tester, you must observe the fuel pressure PID using your scan tool. Another useful test is to use your vacuum gauge to measure engine vacuum at an intake manifold vacuum source. Engine vacuum is not only an indicator of the mechanical condition of the engine, but results of vacuum testing may lead you to find carbon deposits causing rough idle symptoms. Carbon buildup on intake valves in GDI systems are caused by a couple of things. On most GDI systems no fuel is injected into the intake system, so blow-by SEMA Booth #10154
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