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How to Replace an Audi G28 Engine Speed Sensor In this video, Charles the humble mechanic demonstrates how to replace the G28 engine speed sensor. This sensor is located near the transmission's edge over the flywheel gear. It transmits a signal to the ECU through an uncolored wire T55/49, then to the tachometer in the instrument cluster. 1. Engine Speed Sensor The grey wire is located on the edge of transmission, directly above the flywheel ring. The sensor transmits an electrical signal through the grey wire to pin T55/49. The ECU uses this information to regulate boost and fuel. It also sends an indication to the G5 Tachometer in instrument cluster. The sensor serves as a reference point to connect with the G40 Camshaft Position Sensor. The ecu must be aware when the crankshaft is TDC and the location of the camshaft so it can trigger spark and injectors according to the situation. If this sensor fails to function, the ECU will display a P00160 error message. This indicates that the Crank Shaft is out of alignment with the Intake Camshaft. It could also indicate a chain stretch or a jumpy chain link in the upper timing chain. The code won't appear without the additional information provided by other sensors (G4 or G40). It's a bit tricky to test as there are several connector pins, and they all have different functions. The best way to do it is by measuring the resistance between the ECU and the sensor. It should read about 1000 ohms when it is operating at its maximum. Check for signs of coolant or oil in the connector bay if there are problems with this part. 2. Injectors Yesterday, while accelerating at full speed from the highway paytoll, i experienced an abrupt drop in power like the engine is out of gas or injectors aren't firing at all. In the morning, i removed the spark plugs. Three were drenched with gazoline the fourth one was dry. I put a piece of tissue over each hole in the injector and when i start the engine without sparks, the three with gazoline jump out. The 4th one remains shut. I tested the ground connection of ECU pins 14,30, and 48/55. I found zero ohm. I assume that the problem is somewhere else. I also tried to reset PID but without success. audi spare key replacement will start when the G28 is disconnected, but it runs fine with the G28 plugged in. However, the intermittent misfire problem continues to occur at higher RPM. The coolant temperature sensor (G62) shows the wrong temp value -49c even when i unplug it. I also noticed that the oil gauge in the cockpit shows 2 bar but the actual pressure is zero. I don't know what to do. I think I've ruled everything else out. But i am afraid I might have missed something. Let me know if you have any ideas! TIA! 3. Fuel Pump The fuel pump in the g28 is activated by a signal from the RPM sensor. The GM-style sensor is the same as the G4 and both function in the 80, 100, 200, UrS and RS2 cars which is why you can easily locate one at a junkyard or in a local parts store. Test them out – put your DMM in resistance mode and take measurements between pins 1 (with the bump on the connector's end up) and 2 (2nd from the left on the black end of the connector). They must be infinite Ohms. 4. ECU Our 20vt turbo (3B, AAN, ABY and ADU) engines are equipped with an ECU that must know the speed and position of the crankshaft in order to make decisions regarding timing of the fuel injectors, etc. It utilizes a Crank Position Sensor G4 and an Engine Speed Sensor G28 to accomplish this. If you encounter a problem with either of these sensors, the diagnostic scanner will show codes that could lead to an engine shut down. Some of the signs of a failed G28 sensor are an inaccurate gearbox rev counter and gears that shift faster than normal, and/or a misfire when in gear. If you have any of these problems, it is likely that your sensor is going bad and should be replaced. The good thing is that they are quite affordable and easy to find, especially in the case of the Bosch model, which is what ours are. You can also choose the GM version of this unit is also a good choice. 5. Tachometer A failing engine speed sensor could be a cause for numerous issues in your car. It's a crucial component of the transmission in your Audi, as it transmits information to the ECU on how fast or slowly the engine of the car is turning. When this sensor fails, it can affect the performance of the transmission as well as the rest of the car's components. The G5 engine sensor is located at the edge of transmission, above the flywheel ring. It sends signals via a gray wire to the ECU pin T55/49. The ECU then processes this signal to regulate the flow of fuel, timig and boost and then sends it on to the G5 Tachometer located in the instrument cluster. You can check for sensor failure by examining the continuity from the sensor to the tachometer. You can also verify continuity between pin T55/49 of the ECU and pin T6a/1 of the instrument cluster (trace [79trace [79]) and between pin T6a/1 as well as pin T26a/12. It should show around 1000 ohms of resistance between those two pins. This is a common feature across the Audi 80-100-200-RS2 series, starting from the 1985 MC up to the 1997 UrS AN and the 1995 RS2 Du, so you might find them in wrecking yards.