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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. This sensor is located near the transmission's edge over the flywheel gear. It sends a message to the ECU through the grey wire T55/49 and then to the tachometer on the instrument cluster. 1. Engine Speed Sensor The sensor is located at the edge of the transmission above the flywheel ring gear the G28 Engine Speed Sensor sends an electrical signal to ECU pin T55/49 via the grey wire. The ECU utilizes this information to control the amount of fuel and boost. It also sends an indication to the G5 Tachometer located in the instrument cluster. The sensor serves as a reference 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 start spark and injectors accordingly. 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 and possibly indicating the chain stretching or a jump link on the upper timing chain. However, the code won't appear on its own, without additional information from other sensors (G4 and G40). It can be a bit difficult to test since there are several pins on the connector, and each has its own functions. The best way to do it is to measure the resistance between the ECU and the sensor. It should read approximately 1000 ohms when the sensor is in full operation. If you are having problems with this part, check for evidence of oil or coolant in the connector bay. 2. Injectors Yesterday, when i was accelerating to the fullest speed from highway paytoll, I experienced massive power loss like the engine is running out of gas or the injectors aren't firing anymore. In genuine audi key replacement , i removed the spark plugs. Three were drenched in gazoline, the fourth was dry. I placed a tissue over each hole in the injector and when I turn the engine on without sparks, the ones that have gazoline pop right out. The 4th one stays closed. I tried to test the ground connections of ECU pins 14,30, and 48/55. I found 0ohm. I assume that the problem is in another location. I also tried to reset the PID but without success. The car will start when the G28 is unplugged, and it works fine when the G28 connected. However the intermittent misfire issue persists at higher RPM. The temperature sensor for coolant (G62) shows the wrong temp value -49c, even if I unplug it. I also noticed that the oil gauge in the cockpit shows 2 bars when the actual pressure is zero. I'm not certain what to do, i think i've pretty much eliminated everything else. But i am afraid I might 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 by the RPM sensor. The GM-style transmitter is identical to the G4 and they both work in the 80 100 200, UrS and RS2 cars so you can easily find one at a junkyard or at a parts store. It is easy to test them: simply put your DMM into resistance mode and measure the distance between pins 1 and 2 (with the bump on the connector's edge facing up). They must be infinite Ohms. 4. ECU The ECU of our 20vt turbo (3B AAN ABY ADU) engines must know both the position and speed the crankshaft to determine timing of the fuel injector, etc. It makes use of a Crank Position Sensor G4 and an Engine Speed Sensor G28 to accomplish this. If either of these go bad you will get codes on the diagnostic scanner that could cause engine shut down. Some of the signs of a failed G28 sensor include an inaccurate gearbox rev counter the gears are shifting faster than normal and/or misfiring when in gear. It is probable that the sensor is failing and needs to be replaced if you experience any of these signs. The good news is they are very cheap and easily accessible, especially when you're looking at an Bosch unit which is what we have. If you prefer, GM's version of this part is an excellent choice. 5. Tachometer A damaged engine sensor could cause a number of problems in your vehicle. It's an essential component of your Audi's transmission, as it sends information to the ECU about how fast or slow the car's crankshaft is rotating. This sensor could cause the transmission to fail and other car components to be affected. The G5 engine speed sensor is located on the edge 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 this signal to control the flow of fuel, timig and boost as well as transmitting it to the G5 Tachometer located in the instrument cluster. You can determine if the sensor is in 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 and pin T26a/12. You should see a resistance of approximately 1000 ohms in these areas. This is the same across the Audi 80-100-200-RS2 range, from the 1985 MC up to the 1997 UrS An and 1995 RS2 DU, so you might find some good ones in wrecking yards.