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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 located near the edges of the transmission, above the flywheel ring gear. It transmits a signal to the ECU via a grey wire T55/49, then to the tachometer in the instrument cluster. 1. Engine Speed Sensor The grey wire is situated at the edges of the transmission, directly above the flywheel ring. The sensor sends a signal via the grey wire to pin T55/49. The ECU then uses this information to control the boost, fuel, and timig. It also sends an indication 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 has reached TDC and also the location of the camshaft in order to activate the spark and injectors. If this sensor fails, the ECU will throw a P00160 code which means the Crank Shaft and Intake Camshaft are out of sync and could indicate chain stretch or a jumped link on the upper chain of timing. The code will not appear without the additional information supplied by other sensors (G4 or G40). Testing is a bit challenging as there are two different connector pins, and they perform different functions however the best method to test it is by measuring resistance between the sensor and the ECU. It should read around 1000 ohms when the sensor is in full operation. If you're having issues with this part, check for signs of oil or coolant in the connector bay. 2. Injectors Yesterday accelerating full speed from highway paytoll, i experienced massive power loss as if the engine was running out of gas or the injectors are not firing at all. I pulled out the spark plugs this morning, three were soaked with gasoline and the fourth was unclean. When I crank the engine, there are no sparks, i place a tissue on the top of each hole in the injector, the 3 drenched with gazoline pop out, but the 4th one stays shut. I tested the ground connection of ECU pins 14,30, and 48/55. I found zero ohm. I'm assuming the issue is elsewhere. I also tried to reset the PID with no success. The car will start when the G28 is unplugged, and it runs fine with the G28 connected. However the intermittent misfire issue persists at higher RPM. The Key Lab (G62) even if it is not plugged in, shows a temperature of -49c. Also i noticed that the oil pressure gauge in the cockpit shows 2 bar, whereas the actual pressure is 0.0 when i rev the engine. I'm not sure what to do, as i believe that i've ruled out everything else. However, i'm afraid that I might have missed something. If anyone has any suggestions, please chime in! TIA! 3. Fuel Pump The fuel pump of the g28 receives signals from the RPM sensor. The GM-style sender is the same as the G4 and both are used in the 80, 100 200, UrS and RS2 cars so you can easily find one at a salvage yard or from a parts store. It is simple to test them by putting your DMM in resistance mode and take measurements between pins 1 (with the bump on the connector's side up) and 2 (2nd from the left on the black connector's end). They must be infinite ohms. 4. ECU The ECU of our 20vt turbo (3B AAN ABY ADU) engines must be aware of the speed and position of the crankshaft to make decisions regarding timing of the fuel injector, etc. To do this, it makes use of a Crank Position Sensor (G4) and an Engine Speed Sensor (G28). If either of these go badly, you will see codes on the diagnostic scanner which can lead to engine shutdown. A malfunctioning G28 sensor could cause an inaccurate speed counter for the gearbox and a gearbox which shifts more quickly than normal, and/or a misfire in the gear. If you experience any of these issues, it is likely your sensor is going bad and should be replaced. They're inexpensive and easy to locate, especially if they're an Bosch unit like ours. If you prefer, GM's version of this part would be an excellent choice. 5. Tachometer A failing engine speed sensor could be a cause for many issues with your vehicle. It is an important part of the transmission in your Audi since it sends information to the ECU regarding how fast or slow the engine of the car is turning. If the sensor fails, it could disrupt the performance of the transmission as well as the other car's components. The G5 engine speed sensor is located at the outside of the transmission, above the flywheel ring gear and sends a signal to the ECU at pin T55/49, via a grey wire. The ECU then processes the signal to control fuel, timig and boost, and also transmitting it to the G5 Tachometer located in the instrument cluster. You can test for sensor failure by checking continuity from the sensor to the tachometer. Additionally, you can check continuity between pin T55/49 of the ECU and pin T6a/1 of the instrument cluster (trace [79]) and between pin T6a/1 as well as pin T26a/12. You should see approximately 1000 ohms resistance between those points. This is a standard part 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.