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How to Replace an Audi G28 Engine Speed Sensor Charles the Humble Technician shows you how to replace the G28 Engine Speed Sensor. The sensor is located at the top of the transmission just above the flywheel ring gear. It sends a message to the ECU via an uncolored wire T55/49, then to the tachometer located on the instrument cluster. 1. Engine Speed Sensor The grey wire is situated on the edge of transmission, directly above the flywheel ring. This sensor sends signals through the grey wire to pin T55/49. audi a4 car key replacement utilizes this information to regulate boost and fuel. It also sends a signal to the G5 tachometer in the instrument cluster. The sensor is used to connect the G40 Camshaft position Sensor. The ecu must be aware when the crankshaft is TDC and the location of the camshaft so it can activate spark and injectors in the right way. If this sensor fails the ECU will throw an error code P00160 which indicates that the Crank Shaft and Intake Camshaft aren't in sync, possibly indicating the chain is stretched or a jump link on the upper timing chain. The code won't appear without the additional information provided by other sensors (G4 or G40). It can be a bit difficult to test as there are several pins on the connector and they all have different functions. The most effective method to test it is by measuring the resistance between the ECU and the sensor. When the sensor is fully functional, it should read about 1000 ohms. Check for signs of coolant, or oil in the connector bay if you have issues with this component. 2. Injectors Yesterday, while accelerating at full speed from the highway paytoll, i experienced massive power loss like the engine is running out of gas or injectors are not firing any more. I pulled out the spark plugs this morning, 3 were soaked in gasoline, and the fourth was unclean. I placed a tissue over each injector hole and when I start the engine with no sparks, the 3 with gazoline jump right out. The 4th one remains closed. I checked the ground connection of ECU pins 14,30, and 48/55. I got 0ohm. Therefore, i think the issue is in another place. I also tried to reset PID but without success. The car can start when the G28 is unplugged and runs fine when it is connected but it still has intermittent misfire issues at higher RPM. The coolant temperature sensor (G62) shows the wrong temperature value of -49c even when i unplug it. I also noticed that the oil gauge in the cockpit shows 2 bars while the actual pressure is zero. I'm not sure what to do. I think I've all other possibilities out. I'm concerned that i may have missed something. If anyone has suggestions, please chime in! TIA! 3. Fuel Pump The fuel pump in the g28 is activated by a signal sent by the RPM sensor. The GM-style transmitter functions similarly to the G4 sender and both work on the 80,100,200, UrS, and RS2 vehicles. You can easily locate a spare in a wrecking shop or parts store. It is easy to test them – just put your DMM into resistance mode and measure the distance between pins 1 and 2 (with the bump at the connector's end facing up). They must be infinite ohms. 4. ECU Our 20vt turbo (3B, AAN, ABY and ADU) engines have an ECU that must know the position and speed of the crankshaft to make decisions regarding fuel injector timing etc. To accomplish this, it makes use of a Crank Position Sensor (G4) and an Engine Speed Sensor (G28). If either of these goes bad you will get codes on the diagnostic scanner which can cause the engine to shut down. A failing G28 sensor could result in an inaccurate gearbox speed counter, a gearbox that shifts more quickly than normal, and/or a misfire in gear. It is likely that the sensor is failing and needs to be replaced if you experience any of these signs. They're cheap and easy to find especially when they're a Bosch sensor like ours. Alternately, GM's version this part is an excellent choice. 5. Tachometer A damaged engine sensor could cause a number of problems in your vehicle. It's a vital component of your Audi's transmission, because it communicates to the ECU about how fast or slow the car's crankshaft is rotating. When this sensor fails, it could cause problems for the transmission, as well as the rest of the car's components. The G5 engine sensor is located at the outskirts of transmission, above the flywheel ring. It sends signals via an uncolored wire to the ECU pin T55/49. The ECU then processes this signal to control the flow of fuel, timig and boost, and also transmitting it to the G5 tachometer inside the instrument cluster. You can test the sensor for failure by checking continuity between it and the tachometer, between ECU pin T55/49 and the instrument cluster connection via pin T6a/1 (trace [79trace [79]) as well as between T6a/1, and the instrument cluster pin T26a/12. There should be an average resistance of 1000 ohms between these two points. This is a typical part across the Audi 80 100, 200, UrS and RS2 range from 1985 MC to the 1997 UrS AAN and 1995 RS2 ADU, so the best ones might be availble in wrecking yards.