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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. This sensor is located at the top of the transmission just above the flywheel ring gear. It sends a signal to the ECU via the grey wire (T55/49), then to the tachometer in the instrument cluster. 1. Engine Speed Sensor It is located on the outside of the transmission just above the flywheel ring gear the G28 Engine Speed Sensor sends an electrical signal to ECU pin T55/49 through a grey wire. The ECU utilizes this information to control the amount of fuel and boost. It also sends signals to the G5 tachometer inside the instrument cluster. The sensor is used to correlate with the G40 Camshaft position Sensor. The ecu must know when the crankshaft is TDC and where the camshaft is so it can activate spark and injectors in the right way. If this sensor fails to function, the ECU will display a P00160 error message. This indicates that the Crank Shaft is out of sync with the Intake Camshaft. It could also indicate the possibility of a chain stretch or jump in the chain link of the upper chain. The code will not appear without the additional information provided by other sensors (G4 or G40). Testing can be a bit difficult since there are two connector pins and they perform different functions but the most effective method of testing it is to measure resistance between the sensor and the ECU. When the sensor is operational, it should be reading about 1000 ohms. If you're experiencing issues with this part, check for signs of coolant or oil in the connector bay. 2. Injectors Yesterday accelerating full speed from highway paytoll, I experienced massive power loss like the engine is running out of gas or injectors aren't firing at all. This morning i pull out the spark plugs, three were soaked with gazoline and the fourth was dry. I placed a tissue over each injector hole, and when i start the engine without sparks, the three that have gazoline pop right out. The 4th one remains shut. I checked the ground connection of ECU pins 14,30 and 48/55. I got 0ohm. I'm assuming the issue is somewhere else. I also tried to reset PID but without success. The car will start when the G28 is disconnected, but it runs fine with the G28 plugged in. However, the intermittent misfire problem still occurs at higher RPM. The temperature sensor for the coolant (G62) shows the wrong temp value that is -49c even after unplugging it. I also noticed that the oil gauge in the cockpit shows 2 bars but the actual pressure is 0. I'm not sure what to do, but i believe that i've completely ruled out all other possibilities. I'm afraid i may have missed something. If anyone has any suggestions, please let me know! TIA! 3. Fuel Pump The fuel pump in the g28 can be activated by a signal from the RPM sensor. The GM-style transmitter is similar to the G4 sender and works on the 80,100,200, UrS, and RS2 vehicles. You can easily find an extra in a wrecking shop or parts store. It is simple to test them: simply switch 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 should be infinite ohms. 4. ECU Our 20vt turbo (3B, AAN, ABY and ADU) engines have an ECU that has to be aware of the speed and position of the crankshaft in order to make a decision about fuel injector timing etc. It makes use of a Crank Position Sensor G4 and an Engine Speed Sensor G28 to achieve this. If you encounter a problem with either of these sensors, the diagnostic scanner will display codes that could lead to an engine shutdown. Some of the signs of a failing G28 sensor are an inaccurate rev counter for the gearbox and gears that shift faster than normal, and/or a misfire when in gear. It is possible that the sensor is failing and needs to be replaced if you encounter any of these signs. They're inexpensive and easy to locate particularly if they're a Bosch sensor like ours. Alternately, lost audi key of this unit is also a good option. 5. Tachometer A failing engine speed sensor could be a cause for many problems in your car. It is an important part of the transmission in your Audi since it sends information to the ECU on how fast or slowly the engine of the car is turning. This sensor can cause the transmission to fail and other components of the car to be affected. The G5 engine sensor is located near 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 control fuel, timig, and boost and then sends it on to the G5 tachometer inside the instrument cluster. You can test for sensor failure by examining the continuity from the sensor to the tachometer. Also, you can 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 and pin T26a/12. You should observe approximately 1000 ohms resistance between those points. This part is common across the Audi 80-100-200-RS2 series, starting beginning with the 1985 MC and up to the 1997 UrS An and 1995 RS2 DU, so you might find them in wrecking yards.