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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. The sensor is situated at the top of the transmission above the flywheel ring gear. It transmits a signal the ECU via the grey wire (T55/49), then to the tachometer within the instrument cluster. 1. Engine Speed Sensor The grey wire is located on the edge of transmission, directly above the flywheel ring. This sensor sends 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 is used to correlate with the G40 Camshaft position Sensor. The ecu must know when the crankshaft is TDC and where the camshaft is located so that it can trigger spark and injectors in the right way. If this sensor fails when it fails, the ECU will display an error code P00160. This means that the Crank Shaft is out of alignment with the Intake Camshaft. It could also be a sign of an issue with the chain or a jumpy chain link in the upper timing chain. However, the code won't appear on its own without additional information from other sensors (G4 and G40). It's a bit tricky to test as there are various pins on the connector, and each has its own functions. The best way to do it is by measuring the resistance between the ECU and the sensor. When the sensor is fully operational, it should be reading approximately 1000 ohms. you can check here for evidence of coolant or oil in the connector bay if you are experiencing issues with this component. 2. Injectors Yesterday, while accelerating at full speed from the highway paytoll, I experienced an abrupt drop in power as if the engine was running out of gas or injectors aren't firing at all. I took out the spark plugs this morning, three were soaked with gasoline and the fourth was dry. I put tissue over each injector hole, and when i start the engine with no sparks, the three that have gazoline pop right out. The fourth one remains shut. I tested the ground connection on ECU pins 14/55/30/55/48/55/14/55/48/ I get zero ohm. I'm assuming that the issue is elsewhere. I also tried to reset the PID with no success. The car will start when the G28 is disconnected, but it is running fine with the G28 connected. However the intermittent misfire issue persists at higher RPM. The temperature sensor for the coolant (G62) shows the wrong temperature value of -49c, even if I unplug it. Also i noticed that the gauge for oil pressure in the cockpit shows 2 bar when the actual pressure is 0.0 if i crank up the engine. I'm not sure what to do. I believe that I've eliminated everything else. However, i'm afraid that i might have missed something. Let me know should you have any suggestions! TIA! 3. Fuel Pump The fuel pump in the g28 can be activated by a signal from the RPM sensor. The GM-style transmitter functions similarly to the G4 sender and works on the 80,100,200, UrS, and RS2 vehicles. It is easy to find the spare in a salvage shop or a parts store. Test them out – put your DMM in resistance mode and measure the resistance between pins 1 (with the bump on the connector end up) and 2 (2nd from the left on the black connector's side). They should be infinite Ohms. 4. ECU Our 20vt turbo (3B AAN, ABY and ADU) engines have an ECU that needs to know the speed and position of the crankshaft in order to make a decision about timing of the fuel injectors, etc. To do this, it utilizes a Crank Position Sensor (G4) and an Engine Speed Sensor (G28). If either of these go bad you will get codes on the diagnostic scanner which can lead to engine shutdown. Some of the symptoms of a failing G28 sensor are an inaccurate rev counter in the gearbox, gears shifting quicker than normal, and/or a misfire when in gear. It is probable that the sensor is failing and requires to be replaced if you experience any of these signs. They are cheap and easy-to-find, especially when they're a Bosch model like ours. If you prefer, GM's version of this part is an excellent choice. 5. Tachometer A malfunctioning engine sensor can cause a number of problems within your vehicle. It's a crucial component of the transmission in your Audi, as it transmits information to the ECU about how fast or slow the engine of the car is turning. This sensor could cause the transmission to fail and other components in the car to be affected. The G5 engine sensor is located at the edge of the transmission, just above the flywheel ring. It transmits signals via an uncolored wire to the ECU pin T55/49. The ECU utilizes this signal to regulate fuel and boost, as well as timig. It also relays it to the G5 Tachometer inside the instrument cluster. You can check the sensor for any failure by checking the continuity between it and the tachometer, between the 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. You should see around 1000 ohms of resistance between these two points. This is a common component across the Audi 80 100, 200, UrS and RS2 range from 1985 MC through the 1997 UrS AAN and 1995 RS2 ADU, so the best parts could be found in wrecking yards.