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How to Replace an Audi G28 Engine Speed Sensor In this video, Charles the Humble Mechanic shows how to replace the G28 engine speed sensor. The sensor is located at the edge of transmission over the flywheel 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 on the edge of transmission, above the flywheel ring. The sensor transmits a signal via the grey wire to pin T55/49. The ECU then uses this information to control the flow of fuel, timig and boost. It also sends a signal to the G5 tachometer in the instrument cluster. The sensor is used to correlate the G40 Camshaft position Sensor. The ecu needs to be aware of when the crankshaft has reached TDC and also the position of the camshaft, so that it can activate the spark and injectors. If this sensor fails, the ECU will display an error code P00160. This indicates that the Crank Shaft is out of line with the Intake Camshaft. It could also indicate an issue with the chain or a jump in the chain link of the upper timing chain. However, the code won't appear on its own, without additional information from other sensors (G4 and G40). Testing can be a bit difficult as there are two different connector pins and they have different functions but the most effective way to test it is to measure the resistance between the sensor and the ECU. If the sensor is operational, it should be reading around 1000 ohms. Look for signs of coolant, or oil in the connector bay if you have issues with this part. 2. Injectors Yesterday, when i was accelerating to the fullest speed from highway paytoll, i experienced a big cut 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 and found that 3 were soaked with gasoline and the 4th was dry. When I start the engine with no sparks, i place a tissue on the top of each of the injector holes, the 3 drenched with gazoline jump out but the 4th stays shut. I inspected the ground connection on ECU pins 14/55/30/55/48/55/14/55/48/ I get zero Ohm. So i assume the problem is in another place. I also tried to reset the PID with no success. The car will start when the G28 is disconnected, but it works fine when the G28 connected. However The Keylab persists at higher RPM. The temperature sensor for the coolant (G62) shows the wrong temperature of -49c, even if I unplug it. I also noticed that the oil gauge in the cockpit shows 2 bars when the actual pressure is 0. I'm not certain what to do, but i feel i have pretty much ruled out everything else. I'm concerned that i may have missed something. Let me know If you have any suggestions! TIA! 3. Fuel Pump The fuel pump in the g28 is activated by a signal by the RPM sensor. The GM-style transmitter functions similarly to the G4 sender and works on the 80,100,200, UrS, and RS2 vehicles. You can easily find a spare in a wrecking shop or parts store. It is easy to test them: simply put your DMM into resistance mode and determine 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 are equipped with an ECU that has to know the position and speed of the crankshaft to make decisions about timing of the fuel injectors, etc. It makes use of a Crank Position Sensor G4 and an Engine Speed Sensor G28 to achieve this. If you are experiencing issues with either of these, the diagnostic scanner will display the codes that could trigger the engine shutting down. A failing G28 sensor can cause an inaccurate speed counter for the gearbox, a gearbox that shifts more quickly than normal, or a misfire while in the gear. If you are experiencing any of these problems, it is likely that your sensor is deteriorating and should be replaced. The good thing is that they are very cheap and easy to find particularly in the case of the Bosch model, which is what we have. You can also choose the GM version of this part is also a good choice. 5. Tachometer A failing engine sensor could cause a myriad of issues within your vehicle. It is a crucial part of the Audi's transmission as it sends information to the ECU about how fast or slow the vehicle's crankshaft is spinning. If the sensor fails, it could cause problems for the transmission and the other car's components. The G5 engine sensor is located at the outskirts of the transmission, over the flywheel ring. It transmits an electrical signal through an uncolored wire to the ECU pin T55/49. The ECU then processes this signal to regulate fuel, timig and boost and then sends it on to the G5 tachometer in 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 on pin T6a/1 (trace [79]) and between T6a/1 and the instrument cluster pin T26a/12. You should see the resistance to be around 1000 ohms between these two points. This is a typical part that is found 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 parts could be found in wrecking yards.