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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 on the outside of the transmission over the flywheel gear. It sends a message to the ECU via an uncolored wire T55/49, then to the tachometer in the instrument cluster. 1. Engine Speed Sensor The sensor is located at the edge of the transmission just above the flywheel ring gear, the G28 Engine Speed Sensor sends a signal to ECU pin T55/49 through a grey wire. The ECU utilizes this information to regulate fuel and boost. replacement car key audi sends signals to the G5 Tachometer located in 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 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 are not in sync and possibly indicating chain stretch or a jumped link on the upper timing chain. The code won't appear without the additional information supplied by other sensors (G4 or G40). Testing is a bit tricky as there are two different pins for the connector and they perform different functions but the most effective method to test it is by measuring resistance between the sensor and the ECU. It should read approximately 1000 ohms if the sensor is operating at its maximum. If you are having problems 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 aren't firing at all. Today, i pulled out the spark plugs. Three were drenched with gazoline the fourth was dry. I put a piece of tissue over each injector hole and when i start the engine with no sparks, the three that have gazoline pop right out. The 4th one stays shut. I tried to test the ground connections of ECU pins 14,30, and 48/55. I found 0ohm. So i assume the problem is in another place. I also tried to reset the PID with no success. The car is able to start if the G28 is unplugged and it runs perfectly when it is connected but it still is experiencing intermittent misfires at higher RPM. The temperature sensor for the coolant (G62) shows the wrong temperature of -49c even when i unplug it. I also noticed that the oil gauge in the cockpit shows 2 bars but the actual pressure is zero. I don't know what to do. I believe that I've all other possibilities out. But i'm worried that I might have missed something. If anyone has suggestions, please chime in! TIA! 3. Fuel Pump The fuel pump in the g28 gets a signal from 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 which is why you can easily locate one at a salvage yard or at a parts store. It is easy to test them – just switch your DMM into resistance mode and measure the distance between pins 1 and 2 (with the bump at the connector end facing up). They must be infinite Ohms. 4. ECU The ECU in our 20vt turbo (3B AAN ABY) engines requires to know both the position and speed the crankshaft in order to make a decision about timing of the fuel injector, etc. To accomplish this, it utilizes a Crank Position Sensor (G4) and an Engine Speed Sensor (G28). If either of these goes badly, you will see codes on the diagnostic scanner which can lead to engine shutdown. A damaged G28 sensor could cause an inaccurate gearbox speed counter or a gearbox that shifts more quickly than normal, and/or a misfire in the gear. It is probable that the sensor is failing and needs to be replaced if you encounter any of these symptoms. They're inexpensive and easy to locate especially if they're an Bosch unit like ours. Alternatively, the GM version of this unit is also a good option. 5. Tachometer A failing engine sensor could cause a variety of issues in your car. It's an essential component of your Audi's transmission, since it relays information to the ECU about how the car's crankshaft is spinning. If the sensor fails, it will affect the performance of the transmission, as well as the other car's components. The G5 engine speed sensor is located on the outside of the transmission just above the flywheel ring gear. It sends a signal directly to the ECU at pin T55/49 through an uncolored wire. The ECU then uses and processes this signal to regulate the flow of fuel, timig and boost, and also sends it on to the G5 tachometer inside the instrument cluster. You can check for sensor failure by examining the continuity of 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 [79]) and between pin T6a/1 as well as pin T26a/12. You should see the resistance to be around 1000 ohms between these points. This is a standard part 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 ones could be available in wrecking yards.