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How to Replace an Audi G28 Engine Speed Sensor Charles the Humble Technician shows how to replace the G28 Engine Speed Sensor. This sensor is located near the transmission's edge just above 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 at the edges of the transmission, above the flywheel ring. The sensor sends a signal via the grey wire to pin T55/49. The ECU utilizes this information to control 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 has to know when the crankshaft has reached TDC, and the position of the camshaft, in order to activate the spark and injectors. If this sensor fails, the ECU will display a P00160 error message. This means that the Crank Shaft is out of sync with the Intake Camshaft. It could also be a sign of a chain stretch 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 is a little tricky to test because there are various connector pins, and they all have different functions. more info here to do it is by measuring the resistance between the ECU and the sensor. It should read approximately 1000 ohms if the sensor is at full operation. Examine for evidence of coolant or oil in the connector bay if you are experiencing problems with this part. 2. Injectors Yesterday, while accelerating from the highway paytoll at full speed I noticed a significant drop in power. It was like the engine was running out of gas. Or my injectors weren't firing. I took out the spark plugs this morning, 3 were soaked with gasoline and the 4th was dry. I put a piece of tissue over each injector hole, and when I start the engine without sparks, the 3 with gazoline jump out. The 4th one stays closed. I tested the ground connection on ECU pins 14/55, 30/55 and 48/55. I got zero Ohm. So i assume the problem is in another place. I also tried to reset PID but without success. The car will start when the G28 is disconnected, but 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 temperature of -49c, even if I unplug it. I also noticed that the oil gauge in the cockpit shows 2 bar while the actual pressure is 0. I'm not certain what to do, but i believe that i've ruled out everything else. I'm afraid i may have missed something. Please let me know if you have any ideas! TIA! 3. Fuel Pump The fuel pump in the g28 is activated by a signal from the RPM sensor. The GM-style transmitter functions similarly to the G4 sender, and both operate on the 80,100,200, UrS, and RS2 vehicles. It is easy to find an extra in a wrecking shop or a parts store. Testing them is easy 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 end of the connector). They must be infinite Ohms. 4. ECU The ECU of our 20vt turbo (3B AAN ABY ADU) engines must know the position and speed the crankshaft in order to make a decision about fuel injector timing, etc. In order to do this it utilizes a Crank Position Sensor (G4) and an Engine Speed Sensor (G28). If you encounter a problem with either one of these, the diagnostic scanner will display codes that could cause an engine shutdown. A failing G28 sensor could cause an inaccurate speed counter for the gearbox or a gearbox that shifts more quickly than normal, and/or a misfire in the gear. If you have any of these issues, it is most likely that your sensor is going bad and needs replacing. They're cheap and easy to find, especially when they're a Bosch model like ours. You can also choose the GM version of this unit is also a good option. 5. Tachometer A malfunctioning engine sensor can cause a myriad of issues in your vehicle. It is a crucial part of your Audi's transmission, as it sends information to the ECU about how the car's crankshaft is rotating. If the sensor fails, it will affect the performance of the transmission and the rest of the car's components. The G5 engine speed sensor is situated on the outside of the transmission above the flywheel ring gear. It sends a signal to the ECU at pin T55/49 through a grey wire. The ECU then processes the signal to control the flow of fuel, timig and boost and then sends it on to the G5 Tachometer located in the instrument cluster. You can check the sensor for any failure by checking the continuity between it and the tachometer, between 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. It should show approximately 1000 ohms resistance between those two pins. This is a standard component across the Audi 80 100, 200, UrS and RS2 range from 1985 MC through the 1997 UrS AAN and 1995 RS2 ADU so good ones could be available in wrecking yards.